ahhhhhhhhh i hate lasers!!!!!!!!

[frank_1257]

each and every laser diode you ever use, these are called schottky diodes.


These diodes come as 1N518X X=1,2,3,4,5,6,7,8,9,0 depending on amperage / voltage I think a commonly used one is 1N5187

Some diode laser packages have this done internally allready but with c-mounts bar laser this is an absolute must to protect these diodes whats 25 cents compared to crying in your drink.


Another cheap trick is to install an MOV (thats a metal oxide varistor) for something like 3.3vdc across them these will absorb spikes forward biased.

A set of 3 130vac for usa MOVs in a triangle between ground neutral and hot,on your power supply connections, can also be very helpful and cheap to kill mysterious transients. These are available at any radio shack.

A good reflection into your diodes can kill em quick bevare of this!

digikey.com may have all 3 of these items
the closer the mov voltage to your diodes operating voltage the better these are used in pc boards/supplies to prevent spikes killing things, 3.3vdc lowest common size out there.

MOV stands for metal oxide varistor it creates a dead short when voltage gets too high!

I have NEVER killed a diode I protected this way and have actually whoops connected diodes in reverse that were protected as such and they survived.

Another thing Always ground your soldering iron to your work surface you can create damage called etopic pregnancy later when it gives birth the ESD damage can cause premature failure of your laser.

Hers another weird one do not ever pop rivet near anything that is a semiconductor the shock wave destroys the semiconductor substrate.

I cant also tell you enough times, always always always keep a short across your diodes leads before soldering .handling or placing in and out of circuit, the immediatly put a protection diode directly of the back of the laser diode and keep shorted till the driver discharged and fully connected.

Always remember to shunt short drain supplies before mounting diodes.

just had a double red go pop.

no idea why, not a clue.

anyone got any 2x 200w diodes???

would luv them before the meet!!

[mixedgas]

LASORB< we must find out about LASORB.

Since the Benner unit hangs out here, I'll ask him.

Steve

[Pangolin]

Hi guys,

Some of you know that we had an intern come to work with Pangolin for around six months. His name is Francesco, and he goes by the PL handle "Uncle Worm". Francesco is a graduate student studying lasers and laser diodes. His project at Pangolin was advanced laser diode driver studies and topics.

Some of the first things he did at Pangolin was to evaluate the existing laser diode drivers out there. We purchased numerous units and also acquired things from friends. These were anything from cheap, home-built drivers on eBay to top-level drivers from Coherent and Wavelength Electronics. After the analysis, we came to one single conclusion. We didn't like literally a single one of them... Amazing! Nobody, and I mean nobody, has taken into consideration the things we believe should be taken into consideration within a laser diode driver.

We then turne our attention to ESD protection since that is a kind of fundamental problem for all laser diodes. We acquired three separate ESD guns for the testing, and we tested every known ESD protection scheme for a laser diode. Yes, including Schottky diodes and varistors. Our conclusion is that -- basically, with few exceptions (those exceptions generally not being applicable to the types of lasers used by PL members), nothing really works.

Folks, there has been a lot of wishful thinking being done with respect to ESD protection. Engineers have put these things around a laser diode, hoping that they would work, but never actually testing them with a real ESD gun. In fact, many Schottky diodes and capacitors were themselves destroyed by ESD.

We then conceived of a few alternative ESD protection schemes and tested them with a real ESD gun. Amazingly (the reason it's so amazing is because nothing else works) our schemes work! We call the resulting device LASORB and you can read about it here: www.lasorb.com

We also built a laser diode driver with LASORB technology built in. LASORB isn't the only feature of this driver. It basically has many of the things we find missing in other laser diode drivers. We built this driver just as a test. Francesco is bugging me to sell them, but so far we just haven't decided what to do with it...

LASORB itself will certainly be for sale as a part people can buy and apply to their driver. We just need to figure out the packaging and encapsulation and that's what we are doing right now.

I will turn our little LASORB power point into a PDF and then attach it to this post in the future.

Best regards,

William Benner

[steve-o]

ESD is here!!! Winter is here. Dryness is here. I thought for sure I blew out an input to the recording studio tonite.*Spark** I'm gonna stay away from the LDs for now!! POP!! goes the Waser// Ahhhh...! ( I need an ESD workplace, bench, mat, wrist-strap, etc....mmm...
-- Lasorb, huh? What's the clamp-time? Hope it's continously conducting or measured in way less than a nanosecond..

[frank_1257]

However if not what would be really cool would be a protective device built for the diode package that could be slid over the diode leads while you had it temorarily shunted.

Like a little pcb that was round and had pressure feedthrough contacts!

Now that could be sweet cheap easy for anyone to use?

Hi guys,

Some of you know that we had an intern come to work with Pangolin for around six months. His name is Francesco, and he goes by the PL handle "Uncle Worm". Francesco is a graduate student studying lasers and laser diodes. His project at Pangolin was advanced laser diode driver studies and topics.

Some of the first things he did at Pangolin was to evaluate the existing laser diode drivers out there. We purchased numerous units and also acquired things from friends. These were anything from cheap, home-built drivers on eBay to top-level drivers from Coherent and Wavelength Electronics. After the analysis, we came to one single conclusion. We didn't like literally a single one of them... Amazing! Nobody, and I mean nobody, has taken into consideration the things we believe should be taken into consideration within a laser diode driver.

We then turne our attention to ESD protection since that is a kind of fundamental problem for all laser diodes. We acquired three separate ESD guns for the testing, and we tested every known ESD protection scheme for a laser diode. Yes, including Schottky diodes and varistors. Our conclusion is that -- basically, with few exceptions (those exceptions generally not being applicable to the types of lasers used by PL members), nothing really works.

Folks, there has been a lot of wishful thinking being done with respect to ESD protection. Engineers have put these things around a laser diode, hoping that they would work, but never actually testing them with a real ESD gun. In fact, many Schottky diodes and capacitors were themselves destroyed by ESD.

We then conceived of a few alternative ESD protection schemes and tested them with a real ESD gun. Amazingly (the reason it's so amazing is because nothing else works) our schemes work! We call the resulting device LASORB and you can read about it here: www.lasorb.com

We also built a laser diode driver with LASORB technology built in. LASORB isn't the only feature of this driver. It basically has many of the things we find missing in other laser diode drivers. We built this driver just as a test. Francesco is bugging me to sell them, but so far we just haven't decided what to do with it...

LASORB itself will certainly be for sale as a part people can buy and apply to their driver. We just need to figure out the packaging and encapsulation and that's what we are doing right now.

I will turn our little LASORB power point into a PDF and then attach it to this post in the future.

Best regards,

William Benner

[Pangolin]

-- Lasorb, huh? What's the clamp-time? Hope it's continously conducting or measured in way less than a nanosecond..

We don't have the equipment to measure it, but the theoretical reaction time is between 200 and 800 picoseconds. Although we don't have the equipment to measure it, empirically we can say that it works, so it must be sub-nanosecond...

Also, while developing this we discovered some funny things. Basically, things people to to protect against ESD but... won't work. For example, big thick piece of copper at the end of a long cable that goes to the laser head? Sorry, it won't work... If the laser diode is more than 5cm (round trip) from the ESD protection means (including a shunt), it won't protect the laser diode against ESD.

I will get our PowerPoint up here to show you guys. It's pretty interesting...

Bill

[frank_1257]

I work with large commercial diode lasers a lot.

Many use multiple diodes wired in series, all on one thermoelectric cooler, or several adjacent ones.

Most diodes I have worked with have the thermally mounted base as the anode(positive).

What is done is that the diode module bar fiber package etc is mounted of a carefully milled flat piece of aluminum or copper usually .2-.25 inches thick and several times the base of the laser diode by a factor of 4 typically this forms a heat spreader usually a piece of indium foil is used to form a conformal gasket underneath as air voids are BAD!

This metal heat spreader is in turn mounted on to your peltier coldplate or in your instance your optical baseplate if passively cooled.

In order to deal with the common anode and to electrically isolate things to prevent bad things from happening as you have experienced a piece of metal foil that is covered on both sides so it does not conduct electricity is placed between it and this final surface.

This is a trade off for electrical isolation versus the drawback of increased thermal resistance.

You must also use plastic nylon shoulder washers and a hole punch to create clean round holes in the material bigger than the screws passing through.

I got some of this in a auction on ebay it is sold by melcor incorporated I believe this material ( a parrafin way coated foil) may also in some instances be installed with a very thin layer of silicone grease.

Know all this is PIA but every laser I see commercially built is mounted like this.

Occasionally I see multiple diode common anode systems, the chances of unwanted current paths is sadly something to consider and work around.

This isolation is a way to battle these problems.

I in example just this past week bought a combo green red laser module with one driver board an engineered well? chinese built laser it had no paperwork or warnings and arrived with a dead green laser I tested on a non-conductive bench and it was allready toast although the red still worked when i notified the seller ebay snoctony he immediatelly said this was why due to both housings coming in contact I suspect it was already shorted like this and will no longer but there the ship time was for Xhit.

If I can learn how to have pictures hosted I will post 3-4 pictures of how this is done.

I suspect that most any commercial laser mfg is going to have an engineered electrical isolation method built in but cheaper lasers and certainlly DIY red is going to encounter this type problem.

I am a liscensed electrician and long time electronic tech but not a complete laser guru but I can assure you this is a MAJOR source of your RED PBS combined diodes going south.

If you do try to forgo this step be damn sure your drivers are suitable for common anode operation!!!!!!!!!!!!!!!!! A one board multi diode driver would be sweet. If electrically isolated it might be possible to run both red diodes series wired? on just one driver as long as both diodes are closely matched( In example the same production run from the mfg.)

just had a double red go pop.

no idea why, not a clue.

anyone got any 2x 200w diodes???

would luv them before the meet!!

[Pangolin]

OK all,

I promised that I would upload the LASORB Power Point. Well, you can find it here:
http://www.pangolin.com/_Files/LASORB.pdf

That's the Power Point we showed on the ILDA cruise.

I hope you like it!

Bill

[steve-o]

Nice! When will they be on the market? Do they ever short (like a transorb) or open?
I'd like 4 pleez . I have (4) 300 dollar diodes I'd like to protect.

Are you guys planning on selling that improved driver circuit?

[frank_1257]

Seems lasorb is about the only way I could have pictured such a thing!

However if not what would be really cool would be a protective device built for the diode package that could be slid over the diode leads while you had it temorarily shunted.

Like a little pcb that was round and had pressure feedthrough contacts!

Now that could be sweet cheap easy for anyone to use?