Repair and Redesign of a 110W surgical laser unit to operational functionality.

Hello All, I was recommended over here from the LPF as I'm dealing with a unit a tad out of their usual size range.

I come to you today with my first laser (beyond those 5mW toy lasers)
I figured if I will go anywhere, I might as well go big so I purchases a second hand greenlight medical laser system. It employs a 100W (110W?) flash pumped laser.

The unit I purchased had it's screen smashed, leaving me to suspect the rest of it could well be ok! http://laserpointerforums.com/images...s/thinking.gif

Before you start worrying or having concerns about a 'newbie' with such a laser. I have read quite a lot of the safety pointers here and I have 2 pairs of greenlight glasses that game with the unit for eye protection (though I'd still treat the laser as if I didn't have them in terms of safety) I have already had the safety discussion on LPF, however I would be very welcome for any information for safe operation / working!

I have yet to fix the cooling system up however I ran the unit on startup and it seems to fault out on the self-test for the flash lamp.... http://laserpointerforums.com/images/smilies/frown.gif

Having opened up the unit, I have attached pictures of the lot, including the flash bulb. (Don't worry. I have not touched it, just held it by the plastic holder. To me the tube looks fine? al-bit the connectors on each end are a little corroded....

It does have a Q-Switch and some very fancy looking water cooled optics under the black cover (that I probibly shouldn't have removed?)


Judging by the electronics. I have a feeling I will need to work out exactly how this whole thing works and redesign the control board as there is a lot of complex functions on it that I can't / won't use. (broken display unit etc.)

I'm rather excited to get this I hope I can fix it but all is not lost if I can't (it was 'only' £260) I wonder if I could Diode pump it if all goes wrong with the flash pumping circuit.

I'm fairly understanding of safety precautions in general, my other main 'hobby' is high voltage, I have a 70kV x-ray transformer plus a few others including a potential transformer.
I am somewhat of a collector of 'cool things' Well, I have a few projects I'm gradually saving up components for (Ion mill, fusor, SLS printer, laser cutter)


Some background to establish who I am on this and what experiences I have:

I'm 19Yrs, I work for a company as an Electronic / Applications Engineer and do a fair bit of electronics / CAD work there including motor design, drive design, demo design, microcontroller programming etc.

I have good experience with power electronics (500J+ capacitors, 70kV transformers, heavy duty switching power stages)

I'm currently doing an HNC in EE.

I have access to plenty of power supplies, oscilloscopes etc.

Attachment 50409Attachment 50410Attachment 50411
Attachment 50412Attachment 50413Attachment 50414
Attachment 50418Attachment 50419Attachment 50415
Attachment 50416Attachment 50417

The lamp must be submerged in flowing, non-conducting DI water. You need to email NEOS and see if "Giant Pulse Suppression" is enabled / integrated on the Q-switch driver.
!
I'm not so sure that is a flashlamp. I think I'm looking at a CW krypton arc lamp.
!
As that appears to have an integrated "BUCK" mode switching lamp driver, you have a long way to go as lamps are finicky and easily can explode. You have to figure out how to start the lamp, shut off the start boost voltage, and regulate the lamp current. Some where in there will be a series injection ignition transformer with greater then 160 VDC at 20-30 amps coming out of the secondary. When it fires, it will typically produce 20-40 KV riding on top of the DC coming from the buck switcher. The lamp is a current controlled device, while it has a slightly positive delta on its voltage/current curve, it is a device that must be current limited or it will run away. At the same time you have to have flow and water quality/tank level monitored.
!
To give you an idea, we usually let water flow thru the de-ionizer cartridge for four to eight hours before starting the lamp. Any serious conductivity in the water and the power supply, lamp, and rod usually die in a few hundred microseconds. Little details like that matter.
!
Diode pumping is out of the parameters for that rod size and doping.
!
Your calling it a 110 Watt, I see something more like sixty based on the lamp size...
!
If it all possible, using the existing controller is a must. Are you sure there is a not a big box with a separate lamp supply in it?
!
Q-Switched 1064 and 532 nanometer laser light is, IMHO, one of the most dangerous things on the planet, especially for a beginner. You need certified and tested safety goggles at these power levels and a safe beam stop. If you have never worked with sixty to two hundred watts of laser light, you HAVE NO IDEA what a safe stop is, and how dangerous the scattered light is. THIS IS NOT A TOY. Telling me not to give you the safety advice, that you heard it all on LPF, is about the quickest thing you can do to make me NOT want to help you. Less then 0.15% of the LPF population has ever been anywhere close to something like this. There are probably less then 10 people participating on LPF that could tell you how to work on one of these.
!
Looking at the device cooling, it appears to be a low duty cycle laser, I'm not seeing a large cooling system there.
Steve

- - - Updated - - -

The lamp must be submerged in flowing, non-conducting DI water. You need to email NEOS and see if "Giant Pulse Suppression" is enabled / integrated on the Q-switch driver.
As that appears to have an integrated "BUCK" mode switching lamp driver, you have a long way to go as lamps are finicky and easily can explode. You have to figure out how to enable the psu, set the current, turn on the boost voltage start the lamp, shut off the start boost voltage, and regulate the lamp current. Some where in there will be a series injection ignition transformer with greater then 160 VDC at 20-30 amps coming out of the secondary. When it fires, it will typically produce 20-40 KV riding on top of the DC coming from the buck switcher. The lamp is a current controlled device, while it has a slightly positive delta on its voltage/current curve, it is a device that must be current limited or it will run away. At the same time you have to have flow and water quality/tank level monitored.
!
To give you an idea, we usually let water flow thru the de-ionizer cartridge for four to eight hours before starting the lamp. Any serious conductivity in the water and the power supply, lamp, and rod usually die in a few hundred microseconds.
!
Diode pumping is out of the parameters for that rod size and doping.
!
Your calling it a 110 Watt, I see something more like twenty to sixty based on the lamp size...
!
If it all possible, using the existing controller is a must.
!
Q-Switched 1064 nanometer laser light is, IMHO, one of the most dangerous things on the planet, especially for a beginner. You need certified and tested safety goggles at these power levels and a safe beam stop. If you have never worked with sixty to two hundred watts of laser light, you HAVE NO IDEA what a safe stop is, and how dangerous the scattered light is. THIS IS NOT A TOY. Telling me not to give you the safety advice, that you heard it all on LPF, is about the quickest thing you can do to make me NOT want to help you. Less then 0.15% of the LPF population has ever been anywhere close to something like this.
!
Looking at the device cooling, it appears to be a low duty cycle laser, I'm not seeing a large cooling system there.
!
Are you sure there is not a separate lamp psu box inside the unit that I am not seeing in your pictures?
Steve

You mentioned pound sterling which leads me to think you may be in the UK. If so... be certain to look up Daniel Briggs on this forum and if at all possible, pay him to come look at it before getting too far along. It's absolutely not something to try and fire up without someone experienced WITH you. Reading stuff on the internet is good but fail able. You WANT someone standing alongside you willing to accept the risks associated with lighting it up.

Quote:

---

Originally Posted by mixedgas

The lamp must be submerged in flowing, non-conducting DI water. You need to email NEOS and see if "Giant Pulse Suppression" is enabled / integrated on the Q-switch driver.
As that appears to have an integrated "BUCK" mode switching lamp driver, you have a long way to go as lamps are finicky and easily can explode. You have to figure out how to start the lamp, shut off the start boost voltage, and regulate the lamp current. Some where in there will be a series injection ignition transformer with greater then 160 VDC at 20-30 amps coming out of the secondary. When it fires, it will typically produce 20-40 KV riding on top of the DC coming from the buck switcher. The lamp is a current controlled device, while it has a slightly positive delta on its voltage/current curve, it is a device that must be current limited or it will run away. At the same time you have to have flow and water quality/tank level monitored.

---

A lot of really interesting information there, I'll take some time to digest it.

Quote:

---

Originally Posted by mixedgas

To give you an idea, we usually let water flow thru the de-ionizer cartridge for four to eight hours before starting the lamp. Any serious conductivity in the water and the power supply, lamp, and rod usually die in a few hundred microseconds.

---

I will note that down. I intend to do a full teardown and check everything out, replace all water and flush it a few times.

Quote:

---

Originally Posted by mixedgas

Diode pumping is out of the parameters for that rod size and doping.

---

A pity, but I already have a near complete system here, I suppose there is no point rebuilding it to a different style.

Quote:

---

Originally Posted by mixedgas

Your calling it a 110 Watt, I see something more like sixty based on the lamp size...

---

Well, 110W is what I read on the 'factory test' paper stuck to it.

Quote:

---

Originally Posted by mixedgas

If it all possible, using the existing controller is a must.

---

I see where you are coming from. I believe I could replace it with sufficient intel and research with some assistance.
I think the current design won't be plausible due to the fact it is controlled by a touch screen which is broken and really has far too much to it to be convenient to use for laser cutting / interesting experiments.

Quote:

---

Originally Posted by mixedgas

Q-Switched 1064 nanometer laser light is, IMHO, one of the most dangerous things on the planet, especially for a beginner.

---

I'd be interested in hearing about this more.

Quote:

---

Originally Posted by mixedgas

You need certified and tested safety goggles at these power levels and a safe beam stop.

---

I am looking into a beamstop now, as for the goggles. Would you agree the goggles that came with the unit (likely from the center that used it) are suitable?
Or do they need to be checked every so often (do they degrade over time? :/)

Quote:

---

Originally Posted by mixedgas

If you have never worked with sixty to two hundred watts of laser light, you HAVE NO IDEA what a safe stop is, and how dangerous the scattered light is.

---

Well, there are two ways to learn, research it (as I am doing now) or find out the hard way and work with it, possibly blinding yourself (something I have no interest in doing)

Quote:

---

Originally Posted by mixedgas

THIS IS NOT A TOY. Telling me not to give you the safety advice, that you heard it all on LPF, is about the quickest thing you can do to make me NOT want to help you. Less then 0.15% of the LPF population has ever been anywhere close to something like this. Less then 0.05% would know how to teach about getting one of these working.
!
Steve

---

Sorry if it sounded that way. I think a better way to read it would be 'I have already had some safety discussions on LPF (enough to cause some concern / scare my balls off) and I'm interested in any other further safety information that can be provided!) That's what I said read back to me like. I have no interest in loss of eyesight. It's rather important for my life as you might have guessed.

I really appreciate your input and would be very grateful for all information you could share with me. I'm not even thinking of turning on the laser / enabling the output (if I can) without someone telling me to go ahead with it.

EDIT:


Regarding Duty Cycle, I'm not too sure, I think it can be used for longer considering there is 2 ports on the back for coolant water to be put through a big heat exchange I'm betting. All of that there is a tank and a diaphragm pump.

I think you have entered the Briggs Zone...
First thing to do is replace the DI filter with a new reliable DI cartridge, else you'll see more lamp faults followed by a lamp explosion or dead lamp power supply.
Even the indirect scatter from your beam stop is hazardous with one of these. So is the intracavity scattered light when any of the covers are off.
You need a way of viewing IR while not taking off your glasses. You need total control of the room you are in. And so forth.
!
Then you need to read Walter Kochner's book on YAG lasers before starting. It spells everything out in plain terms, except for how to operate safely.
!
As this unit has been removed from medical service, you have no idea if its missing beam handling parts. Some of them are quite critical to your safety.

Steve

Jumping from 5 mW to 110 Watts without some training and a local mentor is a bad move.
You need some time around the few watts level before you make the jump.

Kind Regards,

Steve

Quote:

---

Originally Posted by mixedgas

I think you have entered the Briggs Zone...

---

I don't get the reference. Hint? :D

Quote:

---

Originally Posted by mixedgas

First thing to do is replace the DI filter with a new reliable DI cartridge, else you'll see more lamp faults followed by a lamp explosion or dead lamp power supply.

---

Right, I'll look into it.

Quote:

---

Originally Posted by mixedgas

Even the indirect scatter from your beam stop is hazardous with one of these. So is the intracavity scattered light when any of the covers are off.

---

Note Taken

Quote:

---

Originally Posted by mixedgas

You need a way of viewing IR while not taking off your glasses. You need total control of the room you are in. And so forth.

---

What would you suggest.... room control is a problem but I suppose I should have forseen this.
This might shelf the project 'testing' phase for a while as the unit is in the companies workshop and there is a massive window to the side which employees occasionally walk past, even though the beam is below the desk level, Best not to take any chances at all.

Quote:

---

Originally Posted by mixedgas

Then you need to read Walter Kochner's book on YAG lasers before starting. It spells everything out in plain terms, except for how to operate safely.

---

Quote:

---

Originally Posted by mixedgas

As this unit has been removed from medical service, you have no idea if its missing beam handling parts. Some of them are quite critical to your safety.

---

I have the unit shown, no fiber cables etc. Unfortunately.

How do I find out?

Quote:

---

Originally Posted by mixedgas

Jumping from 5 mW to 110 Watts without some training and a local mentor is a bad move.
You need some time around the few watts level before you make the jump.

Kind Regards,

Steve

---

Well, at one point it was nearly 5mW to 400 Watts / 5kW....

As Brad mentioned, Daniel Briggs is a UK Laserist with experience in the high power yag laser arena. You very much need his help. He is a PL member.
Otherwise you need an industrial laser tech, a hospital biomedical engineer with surgical yag experience, or a laser show person with the YAG skill set such as Mr. Briggs.
You'll have to convince them that you can use this safely.
!
I'm not so sure I'd do this at my workplace, well, unless I owned the company or was paid to do it. I work in academic laser labs for a living.
!
Your at the level of laser power where your high quality beam stop needs to be water cooled and the beam spread before impacting it.
!
Again, little details that are only known to those skilled in the art. I'm supposed to write that you should scrap this and move on to another project at this point, because this is a IR Class IV system.
!
I don't know you well enough to continue helping you, and I state that not as a personal insult, but based on past experience with the wrong person getting their hands on one of these and abusing it in public. I have a friend with a 15 mm hole thru the palm of his hand from a YAG psu arcing. That laid him up in bed for something like four months. I have a local competitor with brain damage from leaning his head against the laser and touching the anode of a cap bank. Hence the next question. Why do you want one of these?
!

Steve

Quote:

---

Originally Posted by mixedgas

As Brad mentioned, Daniel Briggs is a UK Laserist with experience in the high power yag laser arena. You very much need his help. He is a PL member.
Otherwise you need an industrial laser tech, a hospital biomedical engineer with surgical yag experience, or a laser show person with the YAG skill set such as Mr. Briggs.

---

Alright then, I will have to have send him a message, I'm not sure where to find the rest of those people... :rolleyes:

Quote:

---

Originally Posted by mixedgas

I'm not so sure I'd do this at my workplace, well, unless I owned the company or was paid to do it. I work in academic laser labs for a living.

---

I'd rather avoid it too but the alternative is taking it back to my parent's house, which means I either have to put it in my bedroom or a cellar workshop that has a river flowing through it during rainy days.
I hate the idea of just sitting on it, too many of my projects are in that phase.

Quote:

---

Originally Posted by mixedgas

Your at the level of laser power where your high quality beam stop needs to be water cooled and the beam spread before impacting it.

---

I'm looking for one right now, depending on the cost I may build one myself.

Quote:

---

Originally Posted by mixedgas

Again, little details that are only known to those skilled in the art. I'm supposed to write that you should scrap this and move on to another project at this point.

---

Well... there is only one way to learn those details. (get Taught e.g. here / Mr. Briggs should he be willing) or teach myself which... honestly makes no sense and I would sooner dump the project and what I have invested in it so far, which would be a pity as there are quite a number of interesting projects I could do here and the restoration itself would be interesting.

Quote:

---

Originally Posted by mixedgas

I don't know you well enough to continue helping you, and I state that not as a personal insult, but based on past experience with the wrong person getting their hands on one of these and abusing it. I have a friend with a 15 mm hole thru the palm of his hand from a YAG psu arcing. That laid him up in bed for something like four months. I have a local competitor with brain damage from leaning his head against the laser and touching the anode of a cap bank. Hence the next question. Why do you want one of these?

---

There are a few projects I had in mind for this:

Laser Cutter
Laser Cooking (considering it's surgical uses, I wonder if you could cut slices of chicken so thin, cooking it at the same time... a curiosity at best.)
DIY SLS printer.
Investigating high voltage discharge controlled by lasers. (I need to look more into that one, Is this laser suitable to ionize air / gasses?)


I would argue that all those injuries you listed there come down to high voltage / stored energy, something I am already familiar with. I have a 70kV x-ray transformer here along with a few 4kJ+ capacitor banks.
as an electronics engineer I know how to handle electrical systems safely. It is lasers I would have doubts about.




EDIT:

based on past experience with the wrong person getting their hands on one of these and abusing it in public


I seriously lack the imagination to even work out how one could abuse such a thing in public, let alone the motive to abuse it in public.
I have no interest in chaos, I'm a techie!

Quote:

---

Originally Posted by mixedgas

As Brad mentioned, Daniel Briggs is a UK Laserist with experience in the high power yag laser arena. You very much need his help. He is a PL member.
Otherwise you need an industrial laser tech, a hospital biomedical engineer with surgical yag experience, or a laser show person with the YAG skill set such as Mr. Briggs.
!
I'm not so sure I'd do this at my workplace, well, unless I owned the company or was paid to do it. I work in academic laser labs for a living.
!
Your at the level of laser power where your high quality beam stop needs to be water cooled and the beam spread before impacting it.
!
Again, little details that are only known to those skilled in the art. I'm supposed to write that you should scrap this and move on to another project at this point, because this is a IR Class IV system.
!
I don't know you well enough to continue helping you, and I state that not as a personal insult, but based on past experience with the wrong person getting their hands on one of these and abusing it.



Steve

---

Informed OP that this is a terrible way to start out on the LPF thread and mentioned that I've got a decent amount of experience, at least for a hobbyist, and I'm still scared shitless of these things ... and for good reason... Sent him in this direction. Suggested contacting either Nigel, Rob or Dan for assistance (hopefully in person) seeing as they are in the UK and have experience with these beasts or at least similar systems at similar power levels.

Full original post...

Quote:

---

Originally Posted by diachi

A Q-switched arc-lamp pumped YAG for your first laser :wtf: ... This is a terrible idea all round. I've been messing around with lasers for 8 years and these things still scare the shit out of me - and I've been around several working models doing 40W@532nm, Q-switched. I know several people with more experience than me that refuse to go near something like this. Not just dangerous from the ridiculous output power (Major fire hazard, burn hazard, eye hazard, hazard to the space time continuum ... OK, that last one's a joke), but there's plenty of electrical components in there that'll quite happily kill you.

Which safety pointers have you read? I don't think there's really anything on this forum that adequately covers the safety measures needed for one of these.

There are a couple of people here (But more so on Photonlexicon) that know how to get these running. - including one guy who pretty much developed his own very similar system intended for show use. They may however refuse to help you due to previous issues with inexperienced operators running such systems. Much of the knowledge isn't public, and for good reason.

Modifying it to a diode pumped system is going to be far from trivial.

Edit: I know 2 or 3 people in the UK that can work on these systems - they are all active over on Photonlexicon.

---

OP has got to be a little better than a certain "Pro DJ" ... hopefully OP listens carefully and follows advice given by the experts here.

Quote:

---

Originally Posted by Diachi

OP has got to be a little better than a certain "Pro DJ"

---

'Pro DJ'? Is it worth me hearing the story?

Quote:

---

Originally Posted by Diachi

... hopefully OP listens carefully and follows advice given by the experts here.

---

[/QUOTE]
That's certainly why I'm here......

Where in the UK are you located?
Did that come from a surplus dealer in Cambridgeshire by any chance?

I'm based in Dorset myself.


It came from some guy reselling it in Merseyside.

Quote:

---

Originally Posted by TCWilliamson

'Pro DJ'? Is it worth me hearing the story?


That's certainly why I'm here......

---

Ehhh ... Long story short is that some "Pro DJ" managed to get his hands on a similar system to yours and wanted to use it for laser shows but ended up taking the "I know it all" approach when the experts here were trying to help him get it converted for show use in a safe and responsible manner. Didn't listen to pretty much any advice, safety related or technical (After all ... he knew best! :rolleyes:)... There's a little more to it than that, but that's essentially what it comes down to.

IIRC that situation is part of the reason information on converting/repairing/running these systems isn't publicly available. Can't say I disagree with keeping it that way myself. These things should be something you work your way up to after some years of experience and earning the trust of someone who knows what they are doing.

Quote:

---

Originally Posted by Diachi

Ehhh ... Long story short is that some "Pro DJ" managed to get his hands on a similar system to yours and wanted to use it for laser shows but ended up taking the "I know it all" approach when the experts here were trying to help him get it converted for show use in a safe and responsible manner. Didn't listen to pretty much any advice, safety related or technical (After all ... he knew best! :rolleyes:)... There's a little more to it than that, but that's essentially what it comes down to.

IIRC that situation is part of the reason information on converting/repairing/running these systems isn't publicly available. Can't say I disagree with keeping it that way myself. These things should be something you work your way up to after some years of experience and earning the trust of someone who knows what they are doing.

---

Well Fuck me, that has got to be the stupidest thing I've heard of.... a home brew 100W laser light in a public show... (They don't use ones that powerful... do they?) even if they do I wouldn't even think of putting any laser creation I made into a public place. (unless it was a laser cutter for example and the unit was locked down with interlocks during operation without any viewing windows)

Please, I do have some sanity....




I am listening to all advice, the only thing I am hesitating to 'avoid' is the topic of sitting on this thing for a few years, I have no interest or uses in the smaller laser diodes as my interests don't lie so much in the lasers themselves to a 'oooh pretttyy' degree, more of a 'lets see what I can invent with this tool added to my belt.'

I want to develop something new that hasn't been thought of before or improve existing technologies.

You may want to make the effort to get up to Lincolnshire on the weekend of the 17 /18th Sept for UKLEM. Lots of knowledgeable people there and Dan Briggs is likely to be there; look for the UKLEM thread on here.

I'm hesitant to mention the miscreant, reading and seeing pictures about his exploits, alleged and actual, gave many of us headaches from fear. Some people here might have felt a duty to arrange an introduction for him with the Federal authorities. Including his plans to scan his audience with 35 watts of green light point blank. I'm told he has straightened up after a few years in college and having to be self employed. Especially concerns about his statements that it was up to his unskilled audience to decide if they wanted to walk past his "Danger" sign on the door to public facilities. In other words, his free will to have fun was possibly more important then the eye safety of others who are un-aware of what they are walking into.
!
That lead to self enforced rules on PL about discussing how to bypass the controller on a common, cheap, big, green, medical laser. The schematic that is out there in the "scene" has serious errors, Thank God.
!
My point is this, mentoring people on PL has been a pleasure for me in most cases. I've arranged some graduate school interviews, and helped some PLers get scholarships based on a healthy interest in lasers. There have been a few bad apples, and two or three very dangerous ones. So now I screen whom I help. Usually the discussion on high power goes off list. Usually phone calls and/or personal visits are involved before discussions. Fair Enough?
!
PS, He still tries to get me to friend him/recommend him on Linked-In. He claims it was all an act on PL, to get attention..
Steve

Quote:

---

Originally Posted by TCWilliamson

Well Fuck me, that has got to be the stupidest thing I've heard of.... a 100W laser in a public show... (They don't use ones that powerful... do they?) even if they do I wouldn't even think of putting any laser creation I made into a public place. (unless it was a laser cutter for example and the unit was locked down with interlocks during operation without any viewing windows)

Please, I do have some sanity....

---

Actually yeah, ~50W (possibly more, I'm not caught up on recent developments...) Q-switched, frequency doubled YAGs have been used in public shows for years - decades really - nothing wrong with that if you know what you're doing. Things go very wrong, very fast, when you don't know what you're doing.

Not a YAG laser, IIRC it was a CuBr (Copper Bromide laser) but still 10s of watts and pulsed, much like the YAG lasers we're talking of: http://www.telegraph.co.uk/news/worl...blinds-30.html

Quote:

---

Originally Posted by NobleGas

You may want to make the effort to get up to Lincolnshire on the weekend of the 17 /18th Sept for UKLEM. Lots of knowledgeable people there and Dan Briggs is likely to be there; look for the UKLEM thread on here.

---

Oh yeah, that's a good point! Might even be a similar system or two there - there has been in previous years. That'll give you an idea of the incredible amount of power these things produce and may scare you out of working on this project, for now. Maybe work your way up to the high power CW stuff first... I remember being pretty much flash blinded by a beam at 20W(Or was it Dan's larger 40W...?) scanning briefly over a light post about 50 yards down the car park at one LEM.

Quote:

---

Originally Posted by mixedgas

I'm hesitant to mention the DJ, reading and seeing pictures about his exploits, alleged and actual, gave many of us headaches here. Some people here might have felt a duty to arrange an introduction for him with the Federal authorities. Including his plans to scan his audience with 35 watts of green light point blank. I'm told he has straightened up after a few years in college and having to be self employed.

That lead to self enforced rules on PL about how to bypass the controller on "That" common, big, green, medical laser.

My point is this, mentoring people on PL has been a pleasure for me in most cases. I've arranged graduate school interviews, and helped some PLers get scholarships based on a healthy interest in lasers. There have been a few bad apples, and two or three very dangerous ones. So now I screen whom I help. Usually the discussion on high power goes off list. Fair Enough?

Steve

---

Yeah ... definitely can't argue with that.

Quote:

---

Originally Posted by NobleGas

You may want to make the effort to get up to Lincolnshire on the weekend of the 17 /18th Sept for UKLEM. Lots of knowledgeable people there and Dan Briggs is likely to be there; look for the UKLEM thread on here.

---

I may be going over to Barcelona on a business trip to one of our drives suppliers around that time, I will have to check, however if not. I certainly have every intention off! It'd be nice to do such a trip.

EDIT:
looking grim there... just calculating it out, Trains = £100 plus the last 2 days remaining of my holidays this year, along with hotel, food and £40 entry.
If someone going there lived down towards Dorset I'd happily fuel share with them if they'd be willing, but it's a little much to go out of pocket until I have a car (I used a moped for transportation currently due to cost and fuel efficiency)

Quote:

---

Originally Posted by mixedgas

I'm hesitant to mention the miscreant, reading and seeing pictures about his exploits, alleged and actual, gave many of us headaches from fear. Some people here might have felt a duty to arrange an introduction for him with the Federal authorities. Including his plans to scan his audience with 35 watts of green light point blank. I'm told he has straightened up after a few years in college and having to be self employed.

---

That is.... fairly understandable from what you are saying. After all, a bad apple like that causing such an incident would bring major scrutiny on our forum and this hobby in like.
Scanning an audience with 35Watts? Bloody hell, intimidate thoughts are unsafe / faildangerous Galvo failure, someone ducking down / jumping while looking in the wrong direction. I wonder if a suitable slow scan could cut neck veins... This is getting more scary by the second.
It is good to hear he has straightened out however....

Quote:

---

Originally Posted by mixedgas

Especially about his statements that it was up to his unskilled audience to decide if they wanted to walk past his "Danger" sign on the door to public facilities. In other words, his free will to have fun was possibly more important then the safety of others who are un-aware of what they are walking into.

---

And like that, he has no right to ever touch anything more dangerous then a wired mains socket. I do hope he has came around from such thoughts...

Quote:

---

Originally Posted by mixedgas

That lead to self enforced rules on PL about discussing how to bypass the controller on a common, cheap, big, green, medical laser.
!
My point is this, mentoring people on PL has been a pleasure for me in most cases. I've arranged graduate school interviews, and helped some PLers get scholarships based on a healthy interest in lasers. There have been a few bad apples, and two or three very dangerous ones. So now I screen whom I help. Usually the discussion on high power goes off list. Fair Enough?

---

I'm glad to hear you have helped many people like that. I understand where you are coming from there. Please, screen me all you want. I'd think myself as a responsible, careful person person?

Quote:

---

Originally Posted by Diachi

Actually yeah, ~50W (possibly more, I'm not caught up on recent developments...) Q-switched, frequency doubled YAGs have been used in public shows for years - decades really - nothing wrong with that if you know what you're doing. Things go very wrong, very fast, when you don't know what you're doing.

Not a YAG laser, IIRC it was a CuBr (Copper Bromide laser) but still 10s of watts and pulsed, much like the YAG lasers we're talking of: http://www.telegraph.co.uk/news/worl...blinds-30.html

---

Yeah.... I'm feeling a lot less safe at such shows from now on... though I suppose they secure them well enough so they can't miss aim at people / failsafe galvos so the risk would be as high as getting stabbed, possibly lower, providing our recently discussed DJ isn't manning the stage.

Quote:

---

Originally Posted by Diachi

I remember being pretty much flash blinded by a beam at 20W(Or was it Dan's larger 40W...?) scanning briefly over a light post about 50 yards down the car park at one LEM.

---

Not sure how I feel about knowing that...

Food for thought, the AEL for a Class IIA laser is .95 mW into a 7 mm eye pupil. AEL = Accessable Emission Limits. Class IIA basically means the blink reflex of your eye will protect you 99.9999 percent of the time. Most of us here can tell you that 1 millwatt in the eye hurts like a bitch.
!
For industrial and certain public use the license free limit pops up to 4.95 mW. Prolonged eye exposure to a non-moving, high quality, 5 mW beam hurts like a half kick in the balls, can be very dis-orienting, and you wont do it very often.
!
Some place around 15-20-25 mW CW, temporary scarring of the retina can happen for a very high quality beam, in some individuals. Ten mW of Qswitched light with its very high peak power would be more then enough to scare me. I'd have to look at a chart and do some math, but lets call just 10-20 mW of what you could have as being very damaging with a small beam diameter. I may be way off, but that is the number that sticks in my head for a Q-Switched Yag...
!
We've seen video cameras get dead pixels with 5-10 Milliwatts of CW light, if they have a decent lens.
!
So it does not take much. The exact threshold for retinal damage is difficult to assess in a single post.
!
That Q-Switch in your laser lets it discharge the laser rod in a quick spike or series of spikes. Think capacitor discharge into a shorted load. ND:Yag has a storage time constant of about 250 microseconds, and a huge storage depth per unit volume. For yours, a guess would be a 40 to 150 nanosecond pulse if the Q-switch is active. Which makes the pulsed laser a whole new ballgame in terms of safety! When the Acoustic Q-Switch is active, it causes a loss in the cavity, preventing lasing. Energy gets stored in the rod, waiting to be dumped. When the Q-Switch opens, that rod will lase again in a pulse with very high peak power. If your laser is what I think it is, an optimal rate would be between 6,000 and 15,000 fast pulses per second.
Yet it can also lase CW, and will at greatly reduced power.
!
If your working with VFDs for motors, I'm starting to be encouraged.

Steve

Quote:

---

Originally Posted by mixedgas

Food for thought, the AEL for a Class IIA laser is .95 mW into a 7 mm eye pupil. AEL = Accessable Emission Limits. Class IIA basically means the blink reflex of your eye will protect you 99.9999 percent of the time. Most of us here can tell you that 1 millwatt in the eye hurts like a bitch.
!
For industrial and certain public use the license free limit pops up to 4.95 mW. Prolonged eye exposure to a non-moving, high quality, 5 mW beam hurts like a half kick in the balls, can be very dis-orienting, and you wont do it very often.
!
Some place around 15-20-25 mW, temporary scarring of the retina can happen for a very high quality beam, in some individuals.
!
We've seen video cameras get dead pixels with 5-10 Milliwatts of light, if they have a decent lens.
!
So it does not take much. The exact threshold for retinal damage is difficult to assess in a single post.
!
If your working with VFDs for motors, I'm starting to be encouraged.

Steve

---

Yes, my full time job is with Servo drives primarily (Controlled VFDs)
I also do a lot of experimental / power electronics work in my spare time

http://www.youtube.com/watch?v=92rUj7XKlxQ
Bare in mind this was a year ago, I was 18, I have moved on with bigger stuff now and I'm doing safer / more 'rigid' designs (actual PCB designed controllers)
That video pretty much got me my job. I've changed a lot since then in terms of 'adult knowledge / understanding' now I'm in a work place for over a year and a half now.

I'm more interested in the concept of not allowing any laser light to hit my eyes then a 'small amount' *retardo


EDIT:

Oh, another application I just got reminded of... I've wanted to do trials of a laser soldering system for certain concept that has viable commercial potential.

Go back and see what I added with an edit to the last post.


Steve

A tad expensive, but here you go:

http://www.abebooks.com/servlet/Book...6n%3D100121503

Steve

Quote:

---

Originally Posted by mixedgas

Go back and see what I added with an edit to the last post.

Steve

---

Now, that's right up my street. I just need to learn more about the Q-switcher etc. I will remove the black cover again tomorrow and take some detailed pictures for you guys to see what I'm working with there. From what it's looking like most of the drive electronics can be redone, the control board will have to be replaced anyway simply due to the fact it will not work as the HMI is broken.

Would you advise I do a careful, documented tear-down of the drive / control gear and document it all up so we know what we are working with here, or would it be better to leave it complete for now?


I'm getting really quite excited now. This will be a really interesting learning experience and certainly a project to document up and add to my Projects CV.

Quote:

---

Originally Posted by mixedgas

A tad expensive, but here you go:

http://www.abebooks.com/servlet/Book...6n%3D100121503

Steve

---

Brought :)

Found 'SOLID-STATE LASER ENGINEERING, 6TH REVISED AND UPDATED EDITION Paperback – 2011 by KOECHNER W.' for £22 on Amazon :)

Quote:

---

Originally Posted by TCWilliamson

I'm more interested in the concept of not allowing any laser light to hit my eyes then a 'small amount'

---

It's the laser output that ISN'T visible light that's even more scary. :)
.
You're in good hands with Steve and I think you're demonstrating a favorable level of budding competency in pursuing this should you want to take it all the way. I'm hoping you're able to find a way to get to the laser enthusiast meet. I think it will be very rewarding for you and worth whatever sacrifice it takes to get there. Great bunch of very knowledgeable guys over there to help you with this.

Quote:

---

Originally Posted by Bradfo69

It's the laser output that ISN'T visible light that's even more scary. :)]

---

Indeed, but did I specify which wavelength? :p

Quote:

---

Originally Posted by Bradfo69

You're in good hands with Steve and I think you're demonstrating a favorable level of budding competency in pursuing this should you want to take it all the way. I'm hoping you're able to find a way to get to the laser enthusiast meet. I think it will be very rewarding for you and worth whatever sacrifice it takes to get there. Great bunch of very knowledgeable guys over there to help you with this.

---

Thank you. Yes I really want to go to that meeting, I'll start putting my 'beer money' aside into a vase, I shall probibly be able to go then, It's in nearly two months time anyway..
(do you guys know anyone in the south I could carpool with?)

Just got some more pictures of the unit, under the black cover.....


I'm not sure what the second side is to, they arn't optically linked at all and there is no output port, it seems blocked into that specific area... any idea what is going on there?

Attachment 50441Attachment 50445Attachment 50444
Attachment 50443Attachment 50435Attachment 50436
Attachment 50437Attachment 50438Attachment 50439
Attachment 50440Attachment 50442Attachment 50446

That is the green light generation side, and it will be coupled to the IR side.
!
Now you have a problem, if you scrap the mother board, you need to control and tune the KTP temperature to +/- 0.2 C, precisely set the pulse repetition rate to a region that makes the KTP happy, generate giant pulse suppression to protect the KTP crystal, and prevent any lamp overcurrent excursion, so you do not damage the KTP. The PRF rate may be set inside the NEOS RF Driver for the Q-Switch, and NEOS is part of Gooch and Housego LTD, so their UK office may give you some data on the Q-Switch Driver. Makers of Green systems usually default to the internal pulse clock on the NEOS Q-switch driver, which produces a few tens of Watts of RF to drive the acousto-optic Q-Switch crystal. The Q-Switch crystal will be water cooled. So it needs water. Because you have a green system, there probably will be an internal 20-30 watt beam dump for the computer to calibrate the crystal with. Now you need 24 VDC at beaucoup amps to drive the RF amp in the Driver. Running the RF driver without a controlled impedance load on its output will likely kill it.
!
Also, since you have a KTP, you need to seal up the laser head to prevent ANY entry of dust or moisture onto the KTP Crystal, which are difficult to clean and you need specialized solvents to do so. We try to NEVER have to clean them. The intracavity light comes to a focus inside that crystal, and so the power density is enormous, in order to create the conditions for frequency doubling to green. Thus any dust results in degradation of the crystal because of a massive electric field from the focused light. The optical faces of the crystal are AR coated, but the sides are sensitive to moisture and solvents. So place a new, VERY clean plastic bag over the KTP mount and get a packaged, dust free, desiccant near it. Then button it back up.
!
Because you have a KTP, some of the IR optics may leak laser light to aid in tuning. So this thing will have some stray beams inside that may or may not get terminated. The temptation to peak the cavity alignment with just a single power measuring device must now be avoided, because the crystal is angle sensitive, very angle sensitive and as you move any one mirror, the beam path will rotate/translate inside the crystal and rod. Thus two meters and two or more mirror adjustments are used to preserve centering. Thus V and Z fold KTP based systems are tuned with two power detectors, one using leakage from a high reflector optic, and one on the output.
!

I'd urge you to replace the display at this point. Or at least try to find an equivalent. One thing, in the US a replacement arc lamp would be between 150-250$, so keep in mind you have only one, and find Dan Briggs.
!
is this an Aurora or Orion by AMS / Laserscope / Boston Scientific ? If not, it is certainly a clone of the design. Your in over your head, and this just became a very long term project. especially with the need of two thermal laser power meters for tuning. Most medical lasers are scrapped because the local Biomed does not have the training to tune it back to power, or because the doctor who owns it/uses it moves on or upgrades. Given you have NHS, there may be other reasons. Find Sir Briggs!
!
(Expecting Inbound from Jon about the KTP rules any minute)
!



Steve

Do you sense a recurring suggested theme here involving talking to Dan Briggs? :rolleyes: You want to make the effort, trust us. Great guy and truly knows these beasts in and out.

Well, this thread has progressed rapidly! :)

TC: To expound a bit on what others have been saying - the reason everyone is harping on safety is because this laser really should scare you. I owned one similar to yours for about 2 years, and I finally sold it because I wasn't comfortable working with it, even after spending a weekend tearing it apart and putting it back together with the assistance of two experts.

The danger with a Q-switched laser (as Steve has already pointed out) is that they act a bit like a capacitor for light. They can store up a tremendous amount of energy and then release it all in a short pulse. Even if the average visible output of your laser is only 60 watts (which is already a shitload of power!), the peak pulse power in the IR section of that laser is several 10's of killowatts.

Think about that for a moment: 10's of KW. If that doesn't give you serious pause, then you're not thinking clearly. (And we haven't even talked about the high-voltage next to flowing water hazard yet!)

A first-pulse / giant-pulse suppression circuit is a must if you don't want to destroy your optics and your KTP every time you fire it. Likewise, good water purity is a must if you don't want to blow up your power supply and/or destroy your lamp each time you fire it. (Or worse, get the shit shocked out of you!) These topics are not well-documented, at least not in the traditional materials you'll find on-line. This is why having a mentor is key.

I'll second the suggestion to attend the UKLEM, at any cost! You will meet an amazing bunch of people, have a great time, and learn a ton about lasers and laser safety. And in all likelihood, you'll leave the event with a mentor who can help you get your laser operating safely.

Lasers are an expensive hobby, and big lasers are even more expensive. You have one of the largest (in terms of power output) lasers that is easily available to the general public. About the only thing that tops your unit is a high-power copper-vapor laser, and they also produce a pulsed output and thus have many of the same risks. This point can't be over-stressed: pulsed lasers are the most dangerous lasers you will ever work with - period.

If it sounds like we are beating a dead horse, please understand that it is due to years of experience (and healthy respect) that has lead us here. (Not to mention some of the incredibly stupid things we've seen done with these monsters in the hands of the inexperienced.) We don't want an incident to happen, both to protect you *AND* to protect us, indirectly. Because every time someone does something stupid with a laser, the repercussions affect all of us. And your laser, in the hands of an idiot, is well and truly dangerous.

We're not saying you are an idiot (quite the opposite, actually), but we still need to be certain that you fully understand what you're dealing with.

Adam

Up until now, I was contemplating that 110W was the Warning Label Power. Now that I've seen test sheet photos, well, I think it is something else, like an early Greenlight...
!
Boy, I'd shoot the QC Manager, there is very little useful data on the test sheet. I can't see it being 110W green, due to the lack of beam enclosure tubes and air filters... 50 A lamp???? If its what I think it might be, that is one dangerous beast, but without intra-cavity tubes the lifetime would be short.
!
Well into the VERY DANGEROUS zone...
!
Not to mention the system while robust, is fragile. I'm also NOT seeing a 50 amp lamp PSU or cooling system in any of those pictures...
!
TC, Your really in over your head if you pursue this. I work with this sort of stuff on a daily basis, and these beasts scare me, just like they scare Buffo.
!
What I've given you so far is guidance on where to start learning. There is no where near enough info in my posts to get you going. Were it me, based on your manufacturing interests, I'd keep the rod assembly, the cooling assembly, some of the parts and the lamp PSU, and make myself a two mirror cavity IR industrial laser. That alone is a significant, but dangerous, technical challenge.
!
The green systems are not known for their beam quality, in fact, far from it. The beams wander in the cavity, and mode hop, and the fiber launch accommodates that. However, as built, they are a very poor laser for adapting to manufacturing use due to the beam position problem,,and beam cross section constantly shifting. I have helped to place a 35 watt unit in materials processing service, and the client has constant problems with beam wander at the target. He doesn't care, because his alternative was tens of thousands of dollars per year in knife blades to cut thin brass sheet.
!

Steve

Quote:

---

Originally Posted by mixedgas

That is the green light generation side, and it will be coupled to the IR side.

---

I didn't see it well, it's hard to see where the beams connect but I think I have an idea there now.

Quote:

---

Originally Posted by mixedgas

Now you have a problem, if you scrap the mother board, you need to control and tune the KTP temperature to +/- 0.2 C, precisely set the pulse repetition rate to a region that makes the KTP happy, generate giant pulse suppression to protect the KTP crystal, and prevent any lamp overcurrent excursion, so you do not damage the KTP. The PRF rate may be set inside the NEOS RF Driver for the Q-Switch, and NEOS is part of Gooch and Housego LTD, so their UK office may give you some data on the Q-Switch Driver. Makers of Green systems usually default to the internal pulse clock on the NEOS Q-switch driver, which produces a few tens of Watts of RF to drive the acousto-optic Q-Switch crystal. The Q-Switch crystal will be water cooled. So it needs water. Because you have a green system, there probably will be an internal 20-30 watt beam dump for the computer to calibrate the crystal with. Now you need 24 VDC at beaucoup amps to drive the RF amp in the Driver. Running the RF driver without a controlled impedance load on its output will likely kill it.

---

Well shit that is a lot of work / risks. I think the motherboard is a no-go still, The screen is cracked and I have no useful error messages from it too, the manual doesn't contain any needed information meaning I can't fix it unless I get help from LaserScope... which I have a feeling is unlikely.

Quote:

---

Originally Posted by mixedgas

Also, since you have a KTP, you need to seal up the laser head to prevent ANY entry of dust or moisture onto the KTP Crystal, which are difficult to clean and you need specialized solvents to do so. We try to NEVER have to clean them. The intracavity light comes to a focus inside that crystal, and so the power density is enormous, in order to create the conditions for frequency doubling to green. Thus any dust results in degradation of the crystal because of a massive electric field from the focused light. The optical faces of the crystal are AR coated, but the sides are sensitive to moisture and solvents. So place a new, VERY clean plastic bag over the KTP mount and get a packaged, dust free, desiccant near it. Then button it back up.

---

I have not done this, what I did is I opened the unit up, took the pictures and closed it once more. I figure it would be better to leave it closed now rather then risk opening it once more? Or should I open it and toss a few of those desiccant bags in there through the gap and re-seal it?

Quote:

---

Originally Posted by mixedgas

Because you have a KTP, some of the IR optics may leak laser light to aid in tuning. So this thing will have some stray beams inside that may or may not get terminated. The temptation to peak the cavity alignment with just a single power measuring device must now be avoided, because the crystal is angle sensitive, very angle sensitive and as you move any one mirror, the beam path will rotate/translate inside the crystal and rod. Thus two meters and two or more mirror adjustments are used to preserve centering. Thus V and Z fold KTP based systems are tuned with two power detectors, one using leakage from a high reflector optic, and one on the output.

---

Okay, no-pokey unless I want to completely rebuild it, I got it.

Quote:

---

Originally Posted by mixedgas

I'd urge you to replace the display at this point. Or at least try to find an equivalent. One thing, in the US a replacement arc lamp would be between 150-250$, so keep in mind you have only one, and find Dan Briggs.

---

I shall send him a message now. Worst comes to worst, a lamp isn't out of the question if I know the rest works.

Quote:

---

Originally Posted by mixedgas

is this an Aurora or Orion by AMS / Laserscope / Boston Scientific ? If not, it is certainly a clone of the design. Your in over your head, and this just became a very long term project. especially with the need of two thermal laser power meters for tuning. Most medical lasers are scrapped because the local Biomed does not have the training to tune it back to power, or because the doctor who owns it/uses it moves on or upgrades. Given you have NHS, there may be other reasons. Find Sir Briggs!

---

The unit is a Laserscope Greenlight!

Steve[/QUOTE]

------------------------------------------------------------------------

------------------------------------------------------------------------

Quote:

---

Originally Posted by buffo

Well, this thread has progressed rapidly! :)

TC: To expound a bit on what others have been saying - the reason everyone is harping on safety is because this laser really should scare you. I owned one similar to yours for about 2 years, and I finally sold it because I wasn't comfortable working with it, even after spending a weekend tearing it apart and putting it back together with the assistance of two experts.

The danger with a Q-switched laser (as Steve has already pointed out) is that they act a bit like a capacitor for light. They can store up a tremendous amount of energy and then release it all in a short pulse. Even if the average visible output of your laser is only 60 watts (which is already a shitload of power!), the peak pulse power in the IR section of that laser is several 10's of killowatts.

Think about that for a moment: 10's of KW. If that doesn't give you serious pause, then you're not thinking clearly. (And we haven't even talked about the high-voltage next to flowing water hazard yet!)

---

I'm getting this now. I swear with each post it's getting more dangerous... am I going to find out that it is abomb pumped laser from the military next? :sweat:

Quote:

---

Originally Posted by buffo

A first-pulse / giant-pulse suppression circuit is a must if you don't want to destroy your optics and your KTP every time you fire it. Likewise, good water purity is a must if you don't want to blow up your power supply and/or destroy your lamp each time you fire it. (Or worse, get the shit shocked out of you!) These topics are not well-documented, at least not in the traditional materials you'll find on-line. This is why having a mentor is key.

---

Well, I'm not probing further yet until I have one to guide me through what I should do and uh... mentor me.

Quote:

---

Originally Posted by buffo

I'll second the suggestion to attend the UKLEM, at any cost! You will meet an amazing bunch of people, have a great time, and learn a ton about lasers and laser safety. And in all likelihood, you'll leave the event with a mentor who can help you get your laser operating safely.

---

Alright then, I will. I should be able to squeeze it in without having to cut my payment for the Turbo-molecular pump I'm buying off my friend. Could make myself an awesome sputter chamber with that to make a cavity for a future project (or even one of you guys, think there would be interest in that?)

Quote:

---

Originally Posted by buffo

Lasers are an expensive hobby, and big lasers are even more expensive. You have one of the largest (in terms of power output) lasers that is easily available to the general public. About the only thing that tops your unit is a high-power copper-vapor laser, and they also produce a pulsed output and thus have many of the same risks. This point can't be over-stressed: pulsed lasers are the most dangerous lasers you will ever work with - period.

If it sounds like we are beating a dead horse, please understand that it is due to years of experience (and healthy respect) that has lead us here. (Not to mention some of the incredibly stupid things we've seen done with these monsters in the hands of the inexperienced.) We don't want an incident to happen, both to protect you *AND* to protect us, indirectly. Because every time someone does something stupid with a laser, the repercussions affect all of us. And your laser, in the hands of an idiot, is well and truly dangerous.

We're not saying you are an idiot (quite the opposite, actually), but we still need to be certain that you fully understand what you're dealing with.

Adam

---

I'm going to repeat myself once more. I ain't turning that damn thing on until you say I have no chance of blinding myself with it during operation. Even if that means building an enclosure for tests that I can close during operation with interlocks. I get that.

----------------------------------------------------------------------

----------------------------------------------------------------------

Quote:

---

Originally Posted by mixedgas

Up until now, I was contemplating that 110W was the Warning Label Power. Now that I've seen test sheet photos, well, I think it is something else, like an early Greenlight...

---

Sounds right considering it's called the Laserscope Greenlight. :D

Quote:

---

Originally Posted by mixedgas

Boy, I'd shoot the QC Manager, there is very little useful data on the test sheet. I can't see it being 110W green, due to the lack of beam enclosure tubes and air filters... 50 A lamp???? If its what I think it might be, that is one dangerous beast, but without intra-cavity tubes the lifetime would be short.

---

I can't disagree there.

Quote:

---

Originally Posted by mixedgas

Well into the VERY DANGEROUS zone...

---

I think I recall that being mentioned... At this rate I'll be building a de-militarized zone around it.
Safety is paramount.

Quote:

---

Originally Posted by mixedgas

Not to mention the system while robust, is fragile. I'm also NOT seeing a 50 amp lamp PSU or cooling system in any of those pictures...

---

I think it's just a well designed one. I've seen some impressive 50A power supplies in my time in very compact spaces. Either way, it's got to be there somewhere.

Quote:

---

Originally Posted by mixedgas

TC, Your really in over your head if you pursue this. I work with this sort of stuff on a daily basis, and these beasts scare me, just like they scare Buffo.

---

I'm starting to feel this too, but I'm not backing down, even if I have to go at the longhaul with this, redesign it into a 'simple' non q-switched unit. I want to do something with this.

Quote:

---

Originally Posted by mixedgas

What I've given you so far is guidance on where to start learning. There is no where near enough info in my posts to get you going. Were it me, based on your manufacturing interests, I'd keep the rod assembly, the cooling assembly, some of the parts and the lamp PSU, and make myself a two mirror cavity IR industrial laser. That alone is a significant, but dangerous, technical challenge.

---

Alright then. I do hesitate to take the unit apart at all. I suppose it also makes sense to keep it whole until I have exactly what I want to do planned out... I feel it's a waste to throw the Q-Switch and doubling crystal. I want to do something with them.

Quote:

---

Originally Posted by mixedgas

The green systems are not known for their beam quality, in fact, far from it. The beams wander in the cavity, and mode hop, and the fiber launch accommodates that. However, as built, they are a very poor laser for adapting to manufacturing use due to the beam position problem,,and beam cross section constantly shifting. I have helped to place a 35 watt unit in materials processing service, and the client has constant problems with beam wander at the target. He doesn't care, because his alternative was tens of thousands of dollars per year in knife blades to cut thin brass sheet.
Steve

---

Interesting...



-------------------------------------------------------------------

So, over all, beyond the book I am eagerly waiting to arrive, and going to that show in a couple of month's time.... what should I do? To be honest I'm very excited with this project as I have some clever people who are willing to teach me (from what I can see) and plenty of things to learn. I can bide my time on this and be patient still, I'd rather do that then jump in head first with such a unit, to the same way I started off with a microwave transformer before moving towards a Potential transformer then my big 70kV XRT in my high-voltage 'experiments'




EDIT:

Would I be correct in thinking I could remove the complex and tricky frequency doubler, but keep the Q-Switch in the unit so I can still do Q-switched sharp pulses if I want to in the future? (could allow me to do laser welding as a project?)

Oh, get some experience at the 1-2 Watt class of laser... Go to the regional big library with lots of books and find old laser books. Do the same at a serious university science library.
!
MIT OPEN COURSEWARE "Laser Fundamentals" with Dr. Shaoul Ezekiel. All Eight or more hours of Youtube. Yes, he speaks slowly. Yes its old. Yes, he knows what he is doing and his hardware demos are first class. Be glad its free, I once had to check out one videotape every two weeks and could not wait for the next installment. The tape set cost 250$ when I was a kid.
!
Find a copy of Laser Fundamentals, second edition, by Silfvast. The correct version has a photo of PLs own Laserman532 on the cover, with lots of colored beams from a pair of Ion Lasers.
!
Download and learn to use the cavity modeling part of PSST! Laser Software.
!
Find a University laser lab with serious science lasers locally and carefully make friends. Although if you walked in mine and said you want to get 110 watts going, that would cause some fear until I know you better. However a discussion about your qualifications to attend our college, a campus tour, and an evaluation of your math skills would be probably be forthcoming. Dress conservative, and speak slowly and carefully when making contact. If a Prof or Post-doc tells you it might be 30 days before they can see you, its not uncommon. They are very busy. There are two ways in, Cold Calls, and going thru recruiting/admissions. The later is usually not successful.
What might be more successful is visiting the departmental office in person, and asking for an introduction. Emailing for a tour rarely works.
!
One of my favorite questions to perspective trainees is "What do you want to be when you grow up?" It throws young adults for a loop, as they think its an odd question. Students who immediately say "I am grown up" usually get a far more careful evaluation as to why they want this career choice.. This is because one should never stop learning! Engineers and Academics will question you to death during your visit. A good answer is often "I don't know" or "I have not thought about that yet, Sir."
!
If your host blows a hole in a business card for you, you might just be in the right place. If he/she declines because it gets his expensive pulsed optics dirty, you might be in an even better place. If the laser is not lit during your visit, probably wrong place. (Let them suggest the business card thing, its part of the standard tour, but not something to ask for!)
!
So just say, in better English then this, " I received a big Nd:YAG and the serious laser engineers on line said I should make friends and learn before messing with it." Talk your way into a university grade laser safety course, those are free for enrolled students using lasers on most campuses and take 4-8 hours. Start with the university safety office for the course. There are some good on-line materials, find and read. I like the US Army and University of Chicago Materials.
!

Tour a local laser machining job shop or stereolithography facility.
!

Start figuring out how to make metal beam tunnels that can take a 120 watt hit without serious back reflections or burning out.... That will require a serious wall thickness. Then design a tunnel with fold mirrors, and figure out how to align at low power so you never hit the wall.
!
Learn how to use a milling machine, Manual AND CNC.
!
Learn what Class I is, learn what class IIIA is, Class IIIB is, Learn what Class 4 is. Bonus points if you learn about the long extinct Class V laser safety designation. Learn how to calculate safe levels of laser light from direct and diffuse reflections. Hint, always measure what is there, but the math is a good start. Learn that for CW laser light(Easy) , then go find the pulse duration and wavelength tables and thus learn how to do it for pulsed laser light (Hard!)
!
Keep your grades up, and keep your employer happy.
!
The laser is a third of the equation, the application of the laser is a third, and the supporting electronics, power, cooling, lab, and safety is a third.
!
See if any of the Laser Factories in the UK still exist, there were/are a few that make industrial YAGs.
Go Visit them!
!
Figure out why most of us do not want you to post schematics or blog about EXACTLY how this thing works.
!
Figure out how a three point kinematic mirror mount works. (Hint, Ball, Cone, and Flat)
!
Procedures, Procedures, Procedures. Make written procdures..
!
Find a copy of the Perkin Elmer or Heraeus long arc lamp /flashlamp brochures . The correct ones are 40 pages or more long and spell out how not to kill a lamp. Figure out what lamp you have.
!
Understand that the circulating power in the cavity is far more then what comes out the output coupler. Given a certain output power, and the OC mirror transmission, calculate the circulating power.
!
Learn how to calculate pulsed laser math. Given a pulse duration, repetition rate and average power, calculate the peak power per pulse. Be able to do it backwards.
!
Locate a 100-200 Mhz oscilloscope with a 50 Ohm input, and learn how to make a fast photodiode to detect your beam shape. Hint, 100 Mhz or faster PD is what you need.

!
Learn math, and as much high order math as you can learn while your young. Then practice and retain it.
!
I can keep you busy for weeks...
~
Steve

Quote:

---

Originally Posted by mixedgas

Oh, get some experience at the 1-2 Watt class of laser... Go to the regional big library with lots of books and find old laser books. Do the same at a serious university science library.

!
Find a University laser lab with serious science lasers locally and carefully make friends. Although if you walked in mine and said you want to get 110 watts going, that would cause some fear until I know you better. However a discussion about your qualifications to attend our college, a campus tour, and an evaluation of your math skills would be probably be forthcoming. Dress conservative, and speak slowly and carefully when making contact. If a Prof or Post-doc tells you it might be 30 days before they can see you, its not uncommon. They are very busy. There are two ways in, Cold Calls, and going thru recruiting/admissions. The later is usually not successful.
What might be more successful is visiting the departmental office in person, and asking for an introduction. Emailing for a tour rarely works.
!
One of my favorite questions to perspective trainees is "What do you want to be when you grow up?" It throws young adults for a loop, as they think its an odd question. Students who immediately say "I am grown up" usually get a far more careful evaluation as to why they want this career choice.. This is because one should never stop learning! Engineers and Academics will question you to death during your visit. A good answer is often "I don't know" or "I have not thought about that yet, Sir."
!
If your host blows a hole in a business card for you, you might just be in the right place. If he/she declines because it gets his expensive pulsed optics dirty, you might be in an even better place. If the laser is not lit during your visit, probably wrong place. (Let them suggest the business card thing, its part of the standard tour, but not something to ask for!)
!
So just say, in better English then this, " I received a big Nd:YAG and the serious laser engineers on line said I should make friends and learn before messing with it." Talk your way into a university grade laser safety course, those are free for students using lasers on most campuses and take 4-8 hours. Start with the university safety office for the course. There are some good on-line materials.

---

This is a lot more tricky in the UK, possibly impossible, from what I know UK universities are a lot more closed compared to US universities. Over here you have to be a student to access the library, everyone has campus badges etc. I'll have to discuss with one of my cousins who is at the Southampton university medical side of things. Southampton have a pretty massive laser lab from what I can see, along with a -massive- high voltage lab.

Quote:

---

Originally Posted by mixedgas

Tour a local laser machining job shop or stereolithography facility.

---

That would be really interesting. I'll have to hunt about to see regarding that.

Quote:

---

Originally Posted by mixedgas

Start figuring out how to make metal beam tunnels that can take a 120 watt hit without serious back reflections or burning out.... That will require a serious wall thickness. Then design a tunnel with fold mirrors, and figure out how to align at low power so you never hit the wall.

---

metal beam tunnel? ... right well the first thing to making it is knowing what it even is! Time to research.

Quote:

---

Originally Posted by mixedgas

Learn how to use a milling machine, Manual AND CNC.

---

I lack practical access but I am familiar with the workings enough to operate one with a G-Code manual.
Looking to get a home miniature mill / lathe.


Learn what Class I is, learn what class IIIA is, Class IIIB is, Learn what Class 4 is. Bonus points if you learn about the long extinct Class V laser safety designation. Learn how to calculate safe levels of laser light from direct and diffuse reflections. Hint, always measure what is there, but the math is a good start.
!
Keep your grades up, and keep your employer happy.
!
The laser is a third of the equation, the application of the laser is a third, and the supporting electronics, power, cooling, lab, and safety is a third.

Quote:

---

Originally Posted by mixedgas

See if any of the Laser Factories in the UK still exist, there were/are a few that make industrial YAGs.
Go Visit them!

---

Now that's something to do next year when my work holidays are free (I am full time employed...)

Quote:

---

Originally Posted by mixedgas

Figure out why most of us do not want you to post schematics or blog about EXACTLY how this thing works.

---

I think I have enough of an idea on that now.

Quote:

---

Originally Posted by mixedgas

Understand that the circulating power in the cavity is far more then what comes out the output coupler. Given a certain output power, and the OC mirror transmission, calculate the circulating power.
!
Learn how to calculate pulsed laser math. Given a pulse duration, repetition rate and average power, calculate the peak power per pulse. Be able to do it backwards.

---

Right-ho! I take it a good bit of that is in the book?

Quote:

---

Originally Posted by mixedgas

Locate a 100-200 Mhz oscilloscope with a 50 Ohm input, and learn how to make a fast photodiode to detect your beam shape. Hint, 100 Mhz or faster PD is what you need.

---

I have a 4 channel RIGOL DS1104Z at home, and a 400MHz beautiful beast of a LeCroy at work.
How can you detect a beamshape with a single photodiode... have you got any good references for me to read on that?

Quote:

---

Originally Posted by mixedgas

Learn math, and as much high order math as you can learn while your young. Then practice and retain it.

---

Time to contact my math's tutor once more. I can pick up where I left off (calculus) (He has a PhD in Acoustic Engineering, I'd say I'm in good hands.)

Quote:

---

Originally Posted by mixedgas

I can keep you busy for weeks...
Steve

---

Seems so... :D


I've been talking with Dan Briggs, he seems to have actually opened up, tested and sold a unit very similar to mine.
(slightly lower power it seems, but in exactly the same case / format interestingly enough, some optical differences and cooling differences only.)

We have organized a phone call for Sunday. :)

My bet is that with care, you can approach a librarian and gain access. My librarian friends tell me they are pretty much bored now that most people use the internet. Public librarians find themselves being just computer help desk operators who maintain printers. People who ask for actual books are rare. Thus librarians long for the old days.. UK might have something like our free or low cost "Interlibrary Loan" too.
!
I like the DET-10A from Thorlabs.. Rumor has it they sell the bare photodiode for ~15$ and the schematic may be in the marketing literature for the DET-10A. For a person with your skills, creating a "Bias Tee" and putting the PD at the end of a 50 Ohm impedance RF Stripline cut from a scrap PCB with an exacto knife might be easy. The guys at EEVBLOG forums might enjoy helping you. I buy them for work, its worth investing, rather then building when using them at work. One can do an educated guess which PD it is, on their bare detector page.
!
There are circuits for simple "Avalanche Transistor" led pulse drivers on the web. Mine hits 750 picoseconds with 20 dollars worth of parts. That lets you test your PD.
!
Phil Hobbs has published some excellent literature on understanding laser photo diodes, on the web.
!
Pulsed photodiode stuff is all over the academic web for free. Its a common problem. Your pulses are slow by modern terms.
!
See if your college friends will let you browse "Review of Scientific Instruments" on line.
!
Ok, If I had a son, and I had to teach him the family business, these last two posts would be most of what I start with. I'd toss in Navy NEETs, and Art of Electronics Edition Two, but not three. I'd also toss in the US Army and Navy free pdfs on how to machine. Enjoy...
!
Steve

Quote:

---

Originally Posted by mixedgas

My bet is that with care, you can approach a librarian and gain access. My librarian friends tell me they are pretty much bored now that most people use the internet. Public librarians find themselves being just computer help desk operators who maintain printers. People who ask for actual books are rare. Thus librarians long for the old days.. UK might have something like our free or low cost "Interlibrary Loan" too.

---

Good point! I shall see if I can pop over to one of them when I have the time. I do actually have access to one of the university libraries as it's part of the college. I'll have to investigate.

Quote:

---

Originally Posted by mixedgas

I like the DET-10A from Thorlabs.. Rumor has it they sell the bare photodiode for ~15$ and the schematic may be in the marketing literature for the DET-10A. For a person with your skills, creating a "Bias Tee" and putting the PD at the end of a 50 Ohm impedance RF Stripline cut from a scrap PCB with an exacto knife might be easy. The guys at EEVBLOG forums might enjoy helping you. I buy them for work, its worth investing, rather then building when using them at work. One can do an educated guess which PD it is, on their bare detector page.
!
There are circuits for simple "Avalanche Transistor" led pulse drivers on the web. Mine hits 750 picoseconds with 20 dollars worth of parts. That lets you test your PD.
!
Phil Hobbs has published some excellent literature on understanding laser photo diodes, on the web.
!
Pulsed photodiode stuff is all over the academic web for free. Its a common problem. Your pulses are slow by modern terms.

---

Great. I'm going to order two of the photodiodes plus the other components come Monday.
I imagine this one is suitable: https://www.thorlabs.de/_sd.cfm?path...tnumber=FDS100 ?

Quote:

---

Originally Posted by mixedgas

See if your college friends will let you browse "Review of Scientific Instruments" on line.
I'd toss in Navy NEETs, and Art of Electronics Edition Two, but not three.

---

Thanks Steve, I'll check that out! Really, thanks for all the information you have provided me with.

.... best thread i've read here in ages. I feel i am witnessing the birth of a true laser nut. (or at least a budding electrical engineer)

I must admit i opened the thread expecting to see some one being educated in the difference between mw w W

While he states he is not interested in the oooh pretty colours, i am confident we can make a convert of him.

what happened here .....

did he attended the LEM
did he get the unit working with both eyes in working order
is there a hole burnt in the side of his employees building?
has he accidentally cut any limbs off

did this thread get siphoned of to some password protected portion of the site where, only need to know information is disseminated??

we need updates

Quote:

---

Originally Posted by zerowaitstate

.... best thread i've read here in ages. I feel i am witnessing the birth of a true laser nut. (or at least a budding electrical engineer)

I must admit i opened the thread expecting to see some one being educated in the difference between mw w W

While he states he is not interested in the oooh pretty colours, i am confident we can make a convert of him.

what happened here .....

did he attended the LEM
did he get the unit working with both eyes in working order
is there a hole burnt in the side of his employees building?
has he accidentally cut any limbs off

did this thread get siphoned of to some password protected portion of the site where, only need to know information is disseminated??

we need updates

---

The story of TCWilliamson is one wrought of misery and lack of time....

Quote:

---

did he attended the LEM

---

-TCWilliamson did indeed make a pilgrimage to LEM, staying for 2 days and one nights.

Quote:

---

did he get the unit working with both eyes in working order

---

-He failed to get the blasted thing working.

Quote:

---

is there a hole burnt in the side of his employees building?

---

-Nope.

Quote:

---

has he accidentally cut any limbs off

---

-He types with both hands.

Quote:

---

did this thread get siphoned of to some password protected portion of the site where, only need to know information is disseminated??

---

-We may never know.

Quote:

---

we need updates

---

The laser sits with many other things gathering dust, waiting to be awoken once again...

(TL;DR; Brought unit, realised just how difficult and dangerous this shit is... learnt about danger...
then learnt that it would be expensive and painfully tricky to work with the existing electrionics)


... Still wondering if the bar would be suitable for diode pumping.
... Still working out how to fund cost-effective dangerously high power lasering.

LOL.

Well sad to hear you didn't get the unit working.

I hope you enjoyed the LEM, working with lasers IS dangerously addictive, and expensive. Once you have command of those photons, its very difficult to to relinquish.

Best of luck in your ventures

Quote:

---

Originally Posted by zerowaitstate

LOL.

Well sad to hear you didn't get the unit working.

I hope you enjoyed the LEM, working with lasers IS dangerously addictive, and expensive. Once you have command of those photons, its very difficult to to relinquish.

Best of luck in your ventures

---

That said... I do still have it!

I'm considering trying to take the YAG crystal out and turning it to a diode pumped unit, but I don't know if the YAG is suitable for that.

I brought a little 2W demon yesterday, gonna build a little driver for it and have a 'play around' I'll try not to blind myself! :)

LEM was great. I do hope to go up again when I've got my own vehicle.

Last time, I brought my 70kV XRay Transformer.. pity it died under the ability to pull a full load (Had 230V @ 32A avaliable!)

I arrived too late to see the X Ray transformer in action, although I was there to witness its dismantling; did you get it going again?
Still have the IGBTs waiting for me to start one of the projects they're destined for!

I didn't see this thread when originally posted. I have done a bunch of work with the Greenlight PV lasers like yours. I ended up developing a micro-controller board that fits inside and takes over the lamp and q-switch drivers. There is an external control box with an LCD that lets you set the lamp current and q-switch pulse rate and width. It takes care of the first pulse suppression and has nifty safety features like an interlock loop, water temperature sensor, etc. I had one out at CampLEM FWIW. Ping me if you have any interest.

Hi Junktronix,

Admittedly that would be quite interesting to me... However I really need to find the time and organize renting a proper workshop for myself to engage in this project as currently this unit sits at work wrapped up under plastic sheet. I'll probably sit on this thing for a while.

I'm working on trying to get a galvo and diode working, a huge fall from this monster... much safer first laser project.

Also got a 7mm x 70mm ruby rod I came across online :)

Quote:

---

Originally Posted by Junktronix

I didn't see this thread when originally posted. I have done a bunch of work with the Greenlight PV lasers like yours. I ended up developing a micro-controller board that fits inside and takes over the lamp and q-switch drivers. There is an external control box with an LCD that lets you set the lamp current and q-switch pulse rate and width. It takes care of the first pulse suppression and has nifty safety features like an interlock loop, water temperature sensor, etc. I had one out at CampLEM FWIW. Ping me if you have any interest.

---

Whoa... I had no idea you were still producing laserscope parts dude! I know someone who might need to speak with you soon. He's got a pair of older scopes that he's probably going to need parts for. (One fell off a truck - literally - so it's going to need new flow tubes for sure.) I'll send him your way, if that's OK.

With regard to these PV units, I thought they were all locked down with those encrypted "dose card" electronics boards that would prevent the unit from operating after a given number of shots? If so, how'd you manage to reverse-engineer all that? (Or did you just bypass everything and start from scratch?) Either way, pretty cool...

Adam

I dumped all my KTP/532 parts inventory when I started working on the Greenlight PV's, which IMHO are much better machines. I do still have a few a.l.e. controller boxes available though. My controller for the PV is microcontroller based and takes over the lamp power supply and q-switch driver. Once installed, you can remove the display and smart card reader permanently. It implements first pulse suppression in software and lets you control the lamp current as well as the q-switch pulse rate and pulse width. I can usually get 60+W out of them at 25A lamp current with optimal q-switch settings. 80-110W maxed out.

I just noticed this thread. It has a familiar ring and the responses have been sorta deja vu as well.

TC,

My personal opinion is that you should carefully inventory this laser, place it in storage and build, buy or work on a substantially smaller unit for the near future. The safety issues are certainly real and I don't discount them, but my primary reason is that you will get very frustrated even if you don't get hurt.

To ENJOY this project you need test equipment and skills as well as a proper, spacious and isolated working environment. Based on your posts and the image you provided, I suspect you need all of these things. Your applications sounded a bit like a man with a hammer looking for some nails. You didn't mention just looking at a beam with this much power or knowing that you owned such a beast, but for many of us that is in fact the primary reason we would want this laser. For the applications you mention there are more cost effective and functional laser sources.

I don't want to discourage your interest in lasers; moving more slowly along the power curve will be more fun.