Converting a 532nm 50mw laser pointer to a 200mw 808nm Infrared laser

[mvisconte]

I appreciate the feedback.
I didn't think about the fact that I'm not going to be TRYING to burn anything - focusing the beam and holding on spot with the intent of making it hot.

I'm hoping to use it for photobiomodulation (LLLT). This normally involves illuminating a point for anywhere from a couple of seconds to a minute or more, or "painting" an area for a larger amount of time. With adequate divergence, I wouldn't worry about thermal effects.

I looked at the O-Like offerings, which look great, but if I can get the same power level out of a modified $10 50mW green laser pointer as from a $100 AA pen, I'll try the green LP first.

So I guess my current plan will be to pick up a FastTech 200mW 18650 LP and hope that I can get into the head to remove the assembly. Based on the comments I've seen on conversion efficiency, *IF* I'm lucky, I'll have a 1W source of 808nm with a diverging beam. I'll look at the spot w/ an IR camera to get an idea of spot size at different distances, and then estimate energy density from there.

I appreciate the comments.

 

[diachi]

I appreciate the feedback.
I didn't think about the fact that I'm not going to be TRYING to burn anything - focusing the beam and holding on spot with the intent of making it hot.

I'm hoping to use it for photobiomodulation (LLLT). This normally involves illuminating a point for anywhere from a couple of seconds to a minute or more, or "painting" an area for a larger amount of time. With adequate divergence, I wouldn't worry about thermal effects.

I looked at the O-Like offerings, which look great, but if I can get the same power level out of a modified $10 50mW green laser pointer as from a $100 AA pen, I'll try the green LP first.

So I guess my current plan will be to pick up a FastTech 200mW 18650 LP and hope that I can get into the head to remove the assembly. Based on the comments I've seen on conversion efficiency, *IF* I'm lucky, I'll have a 1W source of 808nm with a diverging beam. I'll look at the spot w/ an IR camera to get an idea of spot size at different distances, and then estimate energy density from there.

I appreciate the comments.

Keep in mind you'll need to pick up laser safety glasses for 808nm. While it's just about completely invisible to the naked eye, 1W of 808nm is no less dangerous than 1W of any other, visible wavelength. Arguably it's actually more dangerous, seeing as you can't see where the beam or any reflections are actually going. Safety glasses are an absolutely must have.

 

[mvisconte]

Thank you for reminding me. It's time I get some real ones. The glasses I got with a small 850nm laser are a joke and don't affect the beam at all.

As an side, I've seen a couple articles recently about using 780nm and 808nm lasers at low fluence and through the eyelid for treating age-related AMD, and previously for remediating methanol poisoning blindness.

Is there anything/place you recommend for the safety glasses?

 

[diachi]

Survival Laser actually sells some, not sure if anyone has tried them but their other glasses are good!

Eagle Pair® 190-540nm & 800-1700nm OD5 Laser Safety Goggles

 

[mvisconte]

Survival Laser actually sells some, not sure if anyone has tried them but their other glasses are good!

Eagle Pair® 190-540nm & 800-1700nm OD5 Laser Safety Goggles

Thanks! Off to read up on OD and safety glasses. O-Like has a pair for about $20 less, but I don't know about shipping, etc.

Maybe I can get all this figured out by the weekend and get an order together.

 

[paul1598419]

I built a 500 mW 808nm from scratch and then later upgraded it to a 1 watt. I used a G2 lens and have an IR camera for focusing the laser. I never measured the divergence, but it was pretty good as it has a 3mm spot at 12 feet. I can't say how much of that 3mm is splash as I could see the faint red dot, and it was much smaller. This was against a black matte target.

 

[mvisconte]

So I'm reading about G1 & G2 lenses - but that's going in the opposite direction that I need to go.
I NEED divergence. But it's neat reading about it. I am thinking that to really get an infinity focus would take two people... one @ the laser and one at the side of a target 30 or 40 ft out to report on the spot size - or with the neat smart phone wizardry, a remote IP cam (with a laser glass lens) and the use adjusting looking at the monitor. Then again, I don't know if it would be worth that much effort. I'm not looking to pop balloons or light matches from 40 ft, but rather to get a reasonable (but lower) energy density in a minimum illumination size - not in a max size. Some of the gadgets I've seen claim a 4.5 cm2 "spot" rather than a 3mm spot.

 

[mvisconte]

Ah, I meant to add that I'm looking at a 200mW green laser from fast tech - mainly for simple reasons: cheap (11 dollars), popular battery (I have dozens of spare 18650's), and at that price, if I totally screw things up, I haven't really lost much and I still have a cheap host. Pull off the cover, take out the lens assembly, try to non-destructively get out the vanadate, etc., and see if it still lases. Then try to get pictures of the beam size (using a Sony Night Shot). Oh, and try some reverse calculations to get a rough handle on power density until I can cobble together something to measure the light/heat on target. Take the current at battery, try to estimate the power dissipated at the laser diode, and then try to find a suitable conversion factor (I've read 45%, but I will have to find that reference again).

What does anybody know about 905nm diodes? ARE there any 3, 4, 5 W diodes that don't require extra special drivers?
The only ones I've seen have been LEDs (or IRLEDs) in the milliwatt range - way low for my needs, or 25W or 75W heads that need 20-30A and 200uS pulse widths... a little beyond my spare time tinkering right now.

 

[mvisconte]

Anybody use FastTech for Laser devices? It won't let me use Paypal because I ordered a 200mW green laser. Are they secure for regular credit cards?

 

[CaliKirk]

You cannot use PayPal to purchase certain items from fast tech. IIRC, lasers are one of the items that PayPal will not let them make a transaction with, (because advertised over 5mw) therefore you have to use their in house credit card service. I have had multiple successful transactions with FT though, and alot of members here have purchased countless amounts of greenies from there as well with no issues. Shipping is slow but prices are great!

 

[mvisconte]

Thank you.
Well, now I'm getting TWO and I blame it on PayPal then.
I moved the 200mW green laser off of my order and completed a bunch of flashlight, flashlight parts, and hobbyist electronics, and then to get the "free for $20 and up" tracking (or whatever), I ordered one 532 in a black host and one in a silver host. Take THAT PayPal! (Ok, I know... they don't care, and FastTech makes out better, and now everybody in the US hates me, but still.)
I'm going to get the O-Like laser glasses.
I'll check back when I start playing around with dismantle-ization and testing.

 

[Alaskan]

One thing to be aware of if converting 532nm DPSS laser pointer into a IR source, the focal length of the IR will be different than it was for the 532nm, when I converted my pointer I had to move the lens much closer to the IR output or it would not focus. If you look at my photo's you will see I had to put the G2 lens on the opposite end of the focus assembly closer to the diode.

 

[mvisconte]

I *JUST* got my two green LPs (FastTech SKUs 3801200 and 3802013) today - about 2 hours ago. I thought it would take a lot longer.
I will take some pictures and take what measurements I can, before I start any alien autopsy.

My initial impression is - there is not much IR filtering going on.
The only thing I have to go on are visual impressions and shots through a cell phone camera, and a Sony Handycam with NightShot (removes the IR filter from the optical path).

Testing:
I did a quick examination of the two units. One has a BSL (Big Scary Laser) decal, the other doesn't. I guess I don't have to be afraid of THAT one.
I did a quick functionality check down the hall. Very bright in the subdued light of the hallway. Not much information to go on there.
I unscrewed the end shield to look at it. Both units have what looks like a lens or film across the opening. As the spot size changes drastically without the end piece, I will assume it contains a lens. (Don't fault me, I didn't know what to expect.)
I did a check of spot size into a piece of tinted, thick-ish paper, looking for the spot on the side opposite the illumination. I tried white paper, but too much splatter light was visible, so I went with a thicker, darker piece of paper and the spot size was much easier to see. This would be a viable way to get a general focus point for initially focusing a laser in, if one were concerned with that aspect. With a helper and a distant target, this might also be a good way to see the actual spot size for finer adjustment.
I took the cover off again and did a quick shot from a short distance. From 18", the resulting spot is approximately 1.5" in diameter.
I shot pictures with the cell phone camera with and without the cover at different distances.
I used the Handycam in NightShot mode to look at the spot and it was easily overwhelming the system. The NightShot DOES respond to regular light, so I decided that wasn't a very good indication.
I found my Kodak Wratten gelatin filter, No. 29, and had some very interesting results:
With the filter in front of the Handycam lens, there was no difference in intensity through the view finder. Ok.
With the filter in front of the laser, there was no difference in the intensity through the view finder. Ok.
I aimed the laser through the filter onto the carpet and checked it visually. There was NO discernible spot on the carpet. I didn't linger with the beam, just in case... no sense losing my one good filter.
I aimed the laser at the carpet and *I* looked through the gelatin filter. There was a minuscule spot of illumination on the carpet.

Findings:
1. I know it's not the same as laser protective glasses, but I am impressed at how well my impromptu testing went. The gelatin filter (No. 29) worked a treat for a quick-n-dirty visual and camera check.
2. The fact that the nightshot mode still showed a very bright, very large spot tells me that plenty of IR is getting through. I assume this is 1064nm. While this is interesting, I am still going to take the dad-blamed thing apart, because I need the 808nm beam.
3. My main interest is in the diverged (and non-DPSS) beam. The very large spot size witnessed when no final lens assy is in place makes me much more confident that I won't be roasting flesh if aimed at a hand or knee during testing.

Before I go any further, I'll try to get some end-cap amperage readings. I'll need these to come up with power density estimates for the 808nm beam, and knowing them will give a general sanity test for "how much power IS that sucker cranking out" - especially if the battery supply math points to low numbers. If it's using 100mW at the battery terminals, it can't put putting out 200mW at the light end. :-D

Thanks for bearing with me.



References:
FastTech:
BSL: https://www.fasttech.com/products/3801203
No label, so this one must be safe, right? : https://www.fasttech.com/products/3801200


Kodak (PDF):
http://motion.kodak.com/KodakGCG/up...b_And_Post_Production/Kodak_Filters/W2-29.pdf

 

[mvisconte]

Quick end-cap test:
The laser pointers are billet as 200mW
End-case amperage and battery voltage measurements from each:
Black one: 420mA, 4.20v ~= 1.76W consumption
Silver one: 320mA, 4.14v ~= 1.32W consumption
I know this doesn't mean anything until I get a power-out reading, I'm just trying to document as I go.

 

[Alaskan]

I removed the whole crystal assembly from mine leaving only the IR diode, so there was no 1064 out of mine after that, only 808nm. This was a "5 mw" chinese laser would put out over 50mw of 532nm, and over 200mw of IR after collimation, 300mw prior to shooting through the G2 lens which was really a "S1" knock off of the G2.

 

[mvisconte]

I've got 4W of 808nm and it's meaningless unless you have a black surface.

I haven't gotten any further than unscrewing the outer lense assembly from my 200mW FastTech (18650) laser pointers - mainly just to see what the laser assembly looks like.

I did a blind "back of hand" test with the laser pointer, with and without the final assembly... I an say that I didn't feel anything for a few seconds.
Then, because I'm a curious kid, I repeated the experiment against some more... tender... skin. I have some scrapes that are still in the healing process, but w/out scabbing, so I used those as a target.

In both cases it didn't "burn", per se, but it felt just like the pricking of a pin. Maybe that's why balloons burst. :crackup:
On the damaged skin, the effect was immediate.
This was at close proximity - essentially touching - so the spot size was close to what is coming from the vanadate assembly.

Maybe this weekend I can get some usable pictures of the units, emitter assembly, spot sizes, splash, etc.

I wish I could get the pictures from the NightShot handy cam... I think that the residual IR in the final beam is interesting, and important for folks to see. But that's essentially a viewer-only device... no tape to transfer to/from and I can't read the memory stick that comes with it.
If I get anything, it will be by using a cell phone camera to view the handycam monitor. Talk about low res!

I can see that I'll have to brush up on my optics and find a way to build a compact beam expander - and possibly columnator, but I don't think that will be a big issue. As long as I reliably know the spot size at a defined close distance, I can try to figure density.