Opnext HL6545MG Diodes

[PNjunction]

if you sliced the cornbread diagonally from two corners, you could figure the area of each half using Pythagorean Theorem.

Someone correct me if I'm wrong.

WRONG! No more math after 3AM for me.

Pythagorean theorem is to find the length of the hypotenuse of a right triangle. The correct formula to use before eating 1/2 of Mike's cornbread is area = base x height / 2.

Back on topic... Does all this talk of cornbread mean nobody's gotten their Opnext's yet?

[JimBo]

I've got 2 of them but haven't been in my workshop for over a week

Jim

[Starburst]

Hi guys!

first stage:

http://www.laserblog.de/uploads/karl/Starburst_Rot1.jpg

http://www.laserblog.de/uploads/karl/Starburst_Rot2.JPG

I have no drivers at the moment. I will keep you up to date!!!

Best regards!

[p1t8ull]

first stage:

Looks very nice Karl
What mirror mounts are they?

Pit.

[marconi]

Lookin real nice..
A lot of peltier action there

[steve-o]

So what is the output wattage going to be?

[Starburst]

http://www.mi-lasers.com/cgi-bin/sho...rchResult.html

I bought it at ebay. Sometimes you see them on ebay!
I want to cool the diodes down to get more power out of it and i hope that the diodes won`t die to fast. I will drive them with 200 mA to get ~ 180 mW out of each diode. And with realistic calculation i want to get something about 600 - 650 mW! My only problem is the beam diameter. I look for a optic to reduct the beamdiameter! I want to use a 3x beam expander in the other way round! do you understand?

Best regards
Karl

[steve-o]

A beam collimator. I heard that a rifle scope would work but I've never tried that. There's probably better optics out there. I don't know much about NAs and optical formulas though. Maybe Spec, Marconi, or the Doctor could help you out-- and Yadda - and all the rest of the knowledgable people around here!

[The_Doctor]

Nice vote of confidence there. I'll try to honour it. First, the likeliest damage is COD, it affects the facet and is a direct product of the output power. It reaches a very high energy density and affects a very small region. What this means is that to pump enough heat out of it fast enough to protect it you'd need cryogenics, efficiently applied. A peltier might slow down long-term deterioration, but I doubt it will help much. The maximum safe output power at -20 degrees C will be almost the same as at room temperature.

NOTE: this means a LOWER drive current because cooling makes the diode more efficient. Calculating the balance for a given temperature is complex, and easier to find by trial and error. Start low, around 100 mW output or even less, with the Peltiers full on. As you turn each driver current up measuring output changes of around 10 mW, wait for the temperature to stabilise before setting all four for the next raise. If each diode is on its own Peltier, it's easier, and safer. Safer, because if one diode of four all set for max, fails, it might fail in a way that drops less voltage. It's driver will dissipate more heat, but that's not a problem. That extra heat is displaced from a common Peltier system, so the whole thing gets colder on top, making the three remaining diodes run more efficiently. As they are already at max safe output this could push them all over the edge together. While you could built a controller for the TEC to lock its temperature steady, the cost, expense, energy consumption, complexity, all rise sharply. It's much easier to use a single tiny Peltier for each diode, that way a simple constant current Peltier drive is good enough, and if a diode fails, it can't take out the others.

From what I saw of the diode I tested, and the results Pit posted, and others, I think a safe limit of 150 mW should be set, and even then I don't know if you can expect more than 1000 hours. Modulation complicates things, so try to use a constant current shunt mod drive if possible, it's the easiest to calculate, and it allows any modulation rate. Don't use average power in a APC drive, as that will overdrive the diode when it tries to drive the expected average power, unless you work out some awkward detail.

Peltiers will get you a brighter beam even at the same power, by shortening the wavelength. I don't know how low a temperature those diodes will stand, but it's usually safe to try at least 10 degrees C below makers specs, if you take care to avoid thermal contraction clamping stresses or condensation.

For the beam width reduction, I think you can use the expander in reverse. If you know the intended size of the input, and the ratio of width change, you can work out how wide its output beam would be. If your beam is narrower, stick it through the output end and you'll get a thin beam out of the input end. Get your beams' divergences as low as possible though, as those will be multiplied by the ratio of change in the width.


Don't rely too heavily on this post, I'm distracted by stuff here, and it might not be very coherent.

[marconi]

Hey Crow..how ya doin mang
...This is my take:

Nice vote of confidence there. I'll try to honour it. First, the likeliest damage is COD, it affects the facet and is a direct product of the output power. It reaches a very high energy density and affects a very small region. What this means is that to pump enough heat out of it fast enough to protect it you'd need cryogenics, efficiently applied. A peltier might slow down long-term deterioration, but I doubt it will help much. The maximum safe output power at -20 degrees C will be almost the same as at room temperature.
: this means a LOWER drive current because cooling makes the diode more efficient. Calculating the balance for a given temperature is complex, and easier to find by trial and error

This is true... You wont get anymore output, just a lower current for the same power when cooled..plus the added benefit of slightly lower wavelength, but not much.. maybe visable to some..

If each diode is on its own Peltier, it's easier, and safer. Safer, because if one diode of four all set for max, fails, it might fail in a way that drops less voltage. It's driver will dissipate more heat, but that's not a problem. That extra heat is displaced from a common Peltier system, so the whole thing gets colder on top, making the three remaining diodes run more efficiently. As they are already at max safe output this could push them all over the edge together. While you could built a controller for the TEC to lock its temperature steady, the cost, expense, energy consumption, complexity, all rise sharply. It's much easier to use a single tiny Peltier for each diode, that way a simple constant current Peltier drive is good enough, and if a diode fails, it can't take out the others.

I dont know about that, I think using separate peltiers would make the TEC requirements more complicated as you would need to separately measure each diode mount.that would mean four separate TEC drivers, plus tooling.
Also, if using a larger diode mount like I did, even without any cooling , they dont over heat.. of course Im not pushing them because they will be cooled, only, just cooling to lower the wavelength.
No voltage drop problems to worry about, if you use 4 separate diode drivers as each driver controls its own diode..
Plus, I dont have to worry about shutting down the diode drivers should the temp go up.. I could add a comparator to do this, I did think about it some but decided it wasnt needed..altho easy to add.

Modulation complicates things, so try to use a constant current shunt mod drive if possible, it's the easiest to calculate, and it allows any modulation rate. Don't use average power in a APC drive, as that will overdrive the diode when it tries to drive the expected average power, unless you work out some awkward detail.

Ive always had problems with shunt modulation..It will confuse you when making measurements (unless you like being confused ) as the current consumption is backwards.
The spike problem is even worse because of taxing of the regulator.
It also makes the compensation circuit harder to deal with as I have found.
Ive never liked any of those circuits and finding a conventional driver that worked good was tuff too, thats why I did my own. But Robins driver is pretty good I must say..needs just a little more work in the frontend, but decent.
True about the APC type.. of course the diode would need a Pd for feedback
but even harder to modulate, that would be a mess for sure.

Peltiers will get you a brighter beam even at the same power, by shortening the wavelength. I don't know how low a temperature those diodes will stand, but it's usually safe to try at least 10 degrees C below makers specs, if you take care to avoid thermal contraction clamping stresses or condensation.

I agree, we really only want to keep the diode happy
Also true, too bad we cant easily seal the whole thing up and use nitrogen,hehe.

[quote] For the beam width reduction, I think you can use the expander in reverse. If you know the intended size of the input, and the ratio of width change, you can work out how wide its output beam would be. If your beam is narrower, stick it through the output end and you'll get a thin beam out of the input end. Get your beams' divergences as low as possible though, as those will be multiplied by the ratio of change in the width.

The trade-off the lower spot size is exit size of the beam is larger, gotta be careful there. I am still working on this.. but so far..not too impressed with expanders , need to work in this area more. but optics aint cheap, mang.

Don't rely too heavily on this post, I'm distracted by stuff here, and it might not be very coherent.

Hehe, I know the feeling., Ive got so much to do, and Ive got this horrible cold thats got me down for the count.. but I couldnt resist.
Ive got to finish adding analog modulation to this 1w green so that I can get it out of here, but I myself am not thinking too clearly..

Hey Starburst... What size and V and A requirements of those peltiers?