808nm, Cool Stuff...! (And possible diode change, a bit of help needed please)

[marshall]

Well, tonight I decided to tear into one of my 532nm pointers...a 65mw @ 293mA+/- draw, simply because I wanted to experience the full output of 808nm IR available. The pot simply will not go higher, and I've always wanted to see what one of the 808nm pump diodes are truely capable of...output-wise.

Everything went well, except collimation (I was using a digital camera to view output at about size at about 20 feet, also my eye protection : ). Maybe I was limited by thread length/placement for the single lens in the module, but the tightest spot I could get (looked slightly smaller than 1mm...) could only be achieved at about 2-3" away, before fanning back out. This had me also thinking, maybe some light inside was not all passing the lens, as the diode emits a line or oval-type shape un-collimated (no lens), with a high divergence. I was suprised once I removed the crystals and focused a dot...as the 808nm wavelength is very similar to a 650nm red appearance, when focused sharply. It indeed did nice smoking work on black plastic. Not the dim red people speak of actually, until a few feet away, and with the beam being diverged.

I'll try not to make this too long, but I do have some important questions...

First of all, while installing and removing the module multiple times, I broke a diode lead near the base. No biggie, as I want to install a much larger diode anyways, possibly wired to an external battery, instead of merely two AAA's.

I also pulled apart one of those "35mw" gun lasers you see all over ebay from Hong Kong I grabbed for $50 bucks, just to compare internals. (On that note, almost none of them truely output 35mw, hence the <35mw sticker, saying class lllA...wierd).

Anyways, this picture shows the 65mw Leadlight module in need of a higher-outputting diode:

http://img230.imageshack.us/img230/3382/modulerear1rw.jpg

Now, after comletely desoldering, how do I get the diode out, and what type of thermo-sealant should I use for the next diode? How do I know what mw range of diode I indeed have already as well?

I know this uses a 5mm diode type, but...could I machine the heatsink to 9mm, make much more surface area for cooling (remember, no heat buildup will arise from crystals anymore as well), and install a high-outputting 9mm diode instead of a 5mm? Again, this is for strickly 808nm output, not 532nm.

Also, will I need different lens's to collimate 808nm light into a low-divergence beam, or is this hard to do past a few inches, due to the wavelength/diodes properties? The goal is lighting cigarettes (friends' that is, as I don't smoke), camp fires, black balloons, etc.

If I go ahead with a much higher outputting diode, where can I find just one or two reasonably priced, and will the drive board need mods as well?

Also, here is what I still see after removing the IR filter and crystals, it's like a tinted green lens just in front of the diode, what does this actually do? Should it also be removed to increase IR efficiency once I find a way in there?:

http://img207.imageshack.us/img207/2056/unknownlens8mt.jpg

I haven't messed with the pot on the other module (the $50 ebay "35mw" unit), but max draw on it is currently about 225mA. It uses a CR123 batt. Does this need to rise near 300mA in this case, like other pointers?

Here is a pic of the two side by side, the (was) 65mw on the left:

http://img223.imageshack.us/img223/1968/twomodules3uu.jpg

I could even flip-flop the bodies if need be, as they both see 3v input.

Any help on this topic would be greatly appreciated!

Thanks guys.

 

[Athoul]

Quick post here as I don;t have much time :/

In no particular order...

First the green lens that you found, is the IR filter..removing it will increase the IR output.

Second, leadlights have 200-300mW diodes(depending on if they are stock or modified, I consider modified to be even if they are preset at the manufacturer with higher nM diodes or even holes for turning up the pot).

You can add higher but if the crystals can't handle higher they risk cravking.

IR is invisible and will make your laser very dangerous. Also colimating Ir is harder since lower wavelengths colimate easier.

About the danger here is the main issue, IR will reflect off of many things that do not appear to be reflective unlike normal light...your chances of blinding yourself or someone else is very very high.

Hmm I don;t know if I left out anything but if so I'll add to it later, hope this helps for now.

 

[marshall]

Thanks for the info.

I realize IR is very dangerous, as is any wavelength invisable and powerful to the human spectrum. I do protect myself, and make sure there are NO reflective possibilities nearby (it aims for a black foam mouse pad).

But I'm still confused...what is the very front turqoise chip? That I assume has to be the IR filter, when removed, apparent wavelength didn't change whatsoever.

What that last crystal was glued to is a round clear looking crystal (or lens possibly), thinner towards the middle. I know the crystal which is very small and cube-shaped w/ the green/purple reflecion must be the frequency-doubler (or splitter from 1064nm to 532nm I believe). But, after I removed this crystal, I saw the 808nm red light, not the invisable 1064nm light. Is this correct? There's no way the focused 1064nm could be seen by the human eye even when tightly focused, correct?

Anyways, passing this apparent center-green-tinted lens or whatnot just in front of the diode has me confused, unless it's just a different IR wavelength filter (which would make sense in a way if it filtered non-808nm light right off the diode).

Should I yank this lens out definitely, or could it possibly help collimate the 808nm diode's output into the final adjustable lens (after passing the two crystals)? It's like there's more lens/crystals than I should be seeing, to produce the full potential desired...looks almost very inefficient, yet still extremely stong at under 300mA.

Thanks again.

 

[Athoul]

hmm the lens/crystals setup should be something like this. diode,focusing lens,ND:YVO4 chip, KTP chip, IF filter, Colimating lens. It is possible there is more then one filter as I have heard of such before...but personally I have not seen one set up that way. The ND:YVO4 is a small almost cube looking crystal of about 2x2 mm or so. In your case the ND:YVO4 and ktp might be attached to each other if you only see one cube crystal.

If you yanked out everything you would not get any 1064nm light, just the 808nm. You would be better off to only use the 808nm anyway with a focusing lens because you would have less power loss. In fact you would have the full 200-300mW of IR power.

 

[jkaiser3000]

I believe the green tinted glass infront of the diode may be an anti-reflection coating, to prevent some of the infrared light from reflecting off the glass and back into the diode. Something similar to what is used on binoculars and telescopes. That way, light emited by the diode (808nm) is transmited almost unimpeded through the glass.

Actually, for your purposes, all you need to remove is the crystal assembly, and leave everything else there, although you'll need to realighn the lenses in order to collimate the "new" wavelength.

I would recomend using more than just one lens for collimation, as it will produce a better beam. Something like a beam expander, where you use a short focal length lens to focus the light to a spot, and then a longer focal lenght lens to collimate the light. The distance between both lenses should be equal to the sum of both focal lengths. When doing this, you may want to point your laser to a wall far away, so you'll essentially be focusing the spot to infinity. That's what collimating is all about, focusing the light to as tight a spot, on a surface as far away as possible.

 

[comozo]

You probably need new lenses that are IR tranparent I will check for you. You'll need two, one negative focal length and one positive focal length. Collimated IR beam will have higher divergence than shorter wavelengths, always.

 

[bg2vo]

Lighting cigarettes is also my long time goal but is virtually impossible by using pen-size laser. I tried this many times with my 2W and 3W 808nm LD and the problem is mainly the lens. There is no need to expand the beam any more because it is already very much dispersed. I tried more than 10 lenses and the best one I found is the high power magnifying glass with f=25mm and diameter of 30mm.

 

[kickassir]

I've just collimated a 808nm ir diode from a broken leadlight.
Its 3 elements you have to remove on this laser. The Ir filter (green glassplate). The crystall(s). And the lens after the crystalls. Two lenses who
lies just in front of the diode and the collimating is all you need. There may be other ways to do this but I found this way very practical.
When you have removed the crystalls and a tiny lens in front of the crystalls,
just assemble the laser without the irfilter. Loosen the collimating lens so you can adjust the lens. Now you can just use your camera to se how the laser focuses and adjust the focus with the collimating lens.
The camera should not be to sensetive to ir because of the high output,
this will make the dot dissappear in its own light.
Find a point where the dot is almost the same size in short and long distance(e.g 30cm and 10m). Then you will have a collimated ir laser.

Be carefull:rock:!!!!

 

[comozo]

I took at look at my Edmund Industrial Optics catalog and it appears you would need what they call 'Tech Spec (tm) NIR Achromats. These lenses are coated to allow high transmission of NIR over a range of wavelengths. Have you posted for this at alt.lasers?

 

[Athoul]

The lens right after the diode in the optical train should be IR efficent, you might only need to add one extra lens...since the one after the IR filter will be suited to visible light.

 

[marshall]

Sorry I haven't responded back in a speedy manner guys, I have been tearing into some old power sources and electronics for usable parts in my free time(not neccessarily for this project, but some- yes), and remembered the thread.

I currently have four 808nm diodes and their driveboards attached. One is a Wicked...but a diode leg broke pulling it from the body... Haven't pulled the diode out, but I'm guessing it may have the most capable diode. But maybe not, as it was a standard 60mw leadlight. Unless they are all 300mw rated...wish I knew.

Anyways, 2 of the modules are from the CR123-powered 20mw-35mw weapon-mount lasers you see all over ebay going cheap from Hong Kong, one is sorta unknown to me at the moment, as it had no body, and then of coarse the wicked module which is out of commission for the time being.

So, I pulled the "<35mw" ebay module out for starters, as it was the cheapest if I'm possibly burning it up anyways(hehe). I'm trying to get a grasp on what the main functions of the drive-board are, and how I can drive more current to each diode...as now there is no need to worry about crystal-heating problems. I like experimenting, and couldn't hesitate to get something together with what I have sitting here.

Well, let's just say everything doesn't really 'fit' when interchanging parts...such as the optics. So I'll just say I'm going to go ahead and build something completely custom from the ground-up. I guess I'll give myself a christmas present : ).

I've got a 1w 9mm diode lined-up for that, as well as an idea of what I'm going to do for the package (I hate losing voltage quickly, or power for that matter, so I'd like to attach an automobile cell-phone regulator I found from radio shack which regulates any source from a 9v batt through 30v, and attach via d/c plugs with a spiral power cord). This way, it is semi-portable, so long as there is a wall w/ a/c or a battery nearby.

Back on track with the current IR leadlight project...I had to try and make somethig work (although I do need to order the right lens's to collimate this thing past 1.7"!!!).

At about 3am, after staring and poking myself with questions, I finally stuck the drive-board and diode holder (and heatsink) from the ebay laser in the leadlight body. It was the only "part" of the module which will fit correctly, as it has a step-out in diameter. So, I couldn't use the front lens designed for this particular module...not that it really mattered.

You guys are right, I do need a different lens setup to focus this thing. All I get with the front (532nm standard) lens, is incorrect light gathering, and no collimation. Since the Wicked's final lens holder body slid in and sat on the ebay module, it was the closest I could come to focusing the light.

My results as follows:

Started w/ the collimation lens near the diode (by the way, this diode also has a visable and clear lens it's clamped to inside the heatsink, but I can't see the same apparent green tint as the Wickeds'). By starting with this lens close, all that could be achieved was very poor divergence. The more I moved it forward (away from the diode), the smaller of a focus I could get, at a closer range. Finally after getting it out to the point where a small dot was focusable, I started noticing two opposing glares (1/8 moon shaped), telling me going out further with the lens would just be bouncing un-collected light from the IR beams oval edges. The output is oval-shaped as well to a substantial degree.

This does the job...it puts out power in a very small area, but only has about a 5mm range falling near 1.7" out, to burn things.

This pointer is fine I guess, I just want to push more power through the diode. The pot peaks at 225-240ish depending on input voltage, and this is very low. Maybe I should short the pot, lol. But in reality, a 500mw collimated setup in this leadlight body would be nice. Maybe I'll grab a diode for it...does anyone offer higher-driving boards that will solder-up? Or is it a resistor I need to change?

On a last note, when I over-drove the board with 3.5v instead of 3v, the diode had less power. Switched back to fresh AAA's and it had full power again with no problems the whole night. When testing mA @ 3.5v (or trying to, to get a throughput reading at least before it fried), I'd see 320-350ma for about a 1/4 sec, then my multimeter would quickly display 'off' while IR was emitting. I imagine there is an overload drop for protection or something of that matter, as more voltage isn't getting me more output.

Hmm, back to the drawing board...

Snapped a quick couple for you guys:

http://img464.imageshack.us/img464/7037/irlaser8hf.jpg

http://img464.imageshack.us/img464/8498/ircloseupmeltingfoam3bx.jpg

 

[Athoul]

Another thing to point out is that the IR wavelength has a greater divergence then 532nm. I'm not sure how effective it will be at more then a few inches from the laser aperature. Anyway post how it goes

 

[marshall]

Hmm...this has become a toughy...now I don't know if I want to stay emitting at 808nm, or couple a stronger diode to a crystal set (ones larger than what I possess).

Can anyone tell me how to test the output of the 808nm diodes I have, without a light meter? Will any LED be suitable for the "standard" poor-man's test method, at 808nm? I'd like to see which is most capable, and if they are all approximately 300mw diodes @ the same input mA. As soon as I enter this post I am going to collimate a diode I feel is strongest with some huge crystals (like 2.5mm width and 2.5mm of height). Crystal depth is a little hard for me to measure, and I'm not exactly sure what the 'optimal' length for the longer and shorter crystals should be, to push a lot of 808nm through them.

I like burning things up to prove myself wrong (yikes, did I just say that?), so I'm going to push 350mA in short bursts and rise from there until failure of this particular diode in front of me. I have two of these specific diodes, and this could give me a good referance point for the other. I fed it an inducted and converted a/c->d/c burst of over 300mA last night, directly to the diode, a few times in a row- but not past 1 second. I know it sounds crazy, but the output uncollimated was emmense. It looked like 150mw of 532nm(!!!) just by feeding it myself, without the drive board attached.

I know...I'm going to solder this baby and it's going to go poof after about 2 seconds, but at least I will have an image stuck in my head...and who knows...maybe it won't go poof?

I'll be back soon with the results!

 

[marshall]

Ahh...

This stupid power supply...what is it with me getting low mA!!!? Now driven through the "safe" circuit I'm pulling 240mA peak. Looks like it has way too much circuit resistance...

So, away with the modded regulator...I'm driving a straight 350mA @ 3.05v as soon as I eat this sandwich.

How are you guys actually driving 400mA with your boards? Or is it the fact that those are the ones w/ 500mw diodes installed? I'm trying to figure which resistor to jump, but a little hesistant until I get a confirmation.

Thanks guys.

 

[Athoul]

I think those are 300mW or 350mW diodes. To get the mA draw you need to turn up the pot and possibly bypass one of the resistors or change it to a lesser one. Anything over about 400mA will reduce the life of the diode though, but shouldn't burn it out right away...some diodes might handle it some won't...it depends on how fussy that paryicular one is.

I don't think you can do the LED test with an IR laser, but if you can it would need an IR LED.