[Pictures] The Infrared component of my Green DPSS laser.

[Elite6809]

Hey there. I'm a lurker here and I don't post often but I have a cheap run-of-the-mill green laser that I purchased off Amazon in January and only recently while playing around with an infrared camera I noticed something quite interesting.

My infrared camera isn't very high quality at all - in fact, it was a £0.99 webcam on offer that I simply took apart and forcibly removed the infrared filter out of. It now functions fairly normally, except infrared light from around 750nm right up past 1100nm (I've not tested it yet) appear as a purply-white colour, and is probably about as sensitive to the infrared light as to red light. It also sees into the near UV too but not as much. To prove my point, here's a picture of a television remote with a presumably 850nm LED lighting up my face:

 

[Leodahsan]

Good way to show IR.
I expected to see unfocused IR light.
Can you show us your laser pointer?

+1 by the way. I like those studies

 

[Elite6809]

Good way to show IR.
I expected to see unfocused IR light.
Can you show us your laser pointer?

+1 by the way. I like those studies

I too expected the infrared to be little more than a glow. Turns out that it's actually as focused as the laser, even my crappy camera can pick up the infrared from the bottom of my garden at night. Here's the red and green lasers together:


The red one is the little one. I got it about 10 years ago, and it runs (comparatively) brightly on three button cells, even though it's designed for two - the overvolting it probably isn't healthy but I have a stock of half-dead batteries so it's kind of necessary. The green laser is, predictably, the longer one. It's unreliable when it comes to power, if the rechargeables I use are fresh it can light up my room very much at night and the beam is semi-visible in daylight but if they're low on power it's laughably dim. Interestingly the green one has absolutely no safety stickers on it at all.

 

[Leodahsan]

Yeah overvolting those reddies isn't that bad.
The internal resistance of those small cells should be enough for protecting the laser diode.

Again, thanks for the pics.

 

[Blaster]

What a great write up and pics , very interesting to really show the IR component of the 532nm especially when i know exactly what you mean by the pressure gives more output on eBay pens mainly green ,but didn't know that if light pressure is applied obviously just enough just click the switch is applied that IR is still getting out even if only a little of green is seen if at all
+ 1

 

[Elite6809]

What a great write up and pics , very interesting to really show the IR component of the 532nm especially when i know exactly what you mean by the pressure gives more output on eBay pens mainly green ,but didn't know that if light pressure is applied obviously just enough just click the switch is applied that IR is still getting out even if only a little of green is seen if at all
+ 1

It did surprise me at first - I'm no expert, but my theory is the frequency-doubling crystal only starts to give off 532nm after a certain threshold of 1064nm is absorbed, so until you jam your finger on the button there's too little infrared light hitting the crystal and so only the infrared is transmitted. I could be completely mistaken, but that seems to make sense. Thanks for the comment.

 

[KapHn8d]

This was a nice little write up, man... thank you for taking the time to share your findings. +1 for that

This got me thinking about a recent discussion about DPSS IR leakage buried deep in another thread that wasn't specifically topic'd for that, so I thought I'd share some similar findings here with the group (even though this DPSS isn't green). I hope you don't mind. I think this is a neat topic for the forum since we don't "SEE" the IR component and thus it can not only throw off LPM readings (a wee bit), but also be dangerous to the eyes sometimes.

Here is a series of images I took to capture the IR emission from a JetLasers 473nm handheld (which I love, btw... the laser is awesome and JetLasers has excellent customer service).

The first two images were taken with a Canon 5D DSLR that has been converted to infrared-only by an aftermarket shop.

The first image (top) is take with the IR converted body AND the addition of a Hoya R72 filter that blocks wavelengths below 720nm. Here is the response curve of the filter:

The second image (middle) was taken with the same IR-only DSLR with no external filter to ensure no near-IR leakage to the camera sensor... so, basically, you might be getting some visible range in this depending on how good the internal conversion glass is on the body. The first shot basically is to prove it's IR only you see.

The third shot (bottom) was taken with another (stock) DSLR that has no filters or modifications to it. You see the gorgeous visible 473nm in the image, but I'm almost certain that my LPMs are quite misleading on this handheld. I don't think the 473 component is anywhere near the total read.

Sorry the perspective isn't identicle in each shot. I wasn't shooting off a tripod, just sitting on my workbench... so the camera(s) moved between takes.

I'd love to hear some more discussion around this and Elite6809's write-up.

Cheers!!
-c

 

[Elite6809]

Oh wow, those IR shots are infinitely better than my webcam hack, haha. It does seem that IR leakage is a fairly large problem in any DPSS laser, it'd just be different wavelengths of infrared being leaked. How would you be able to get around it without a massive unwieldy heatsink? My first thought turned to something like hot glass (the IR filter in cameras but facing inward), which would pass the visible but reflect the IR straight back in, but that would probably start to overheat massively if the laser is powerful enough. I guess it's something we'll just have to be careful of, until raw green/mid-blue diodes become commonplace enough to overtake DPSS. I'm sure it shouldn't take too long before those green 510nm lasers overtake 532nm DPSS lasers!

 

[KapHn8d]

Ok, I didn't even think to do this before when I took the pics because I was just focused on capturing the IR "beam"... but my buddy, hakzaw1 pointed out that I should do a before/after LPM so it would be clear to see how much of what was going on... especially since you can't really visually judge a longer exposure beamshot with a little squirt of fog in the room.

So here ya go:

 

[Leodahsan]

The first image (top) is take with the IR converted body AND the addition of a Hoya R72 filter that blocks wavelengths below 720nm.

Wow... I've never seen a IR beam shot before... :wave:
Thanks for the pics. I'd rep you but I can't now :beer:

:thanks: for the pics.

 

[Smeerworst]

Here's a picture of my 5W IR handheld
I had to put a black metal sheet on the other side sinds it burns everything in it's path.

The camera picks it up as a nice Purple /pink color.

 

[Elite6809]

Here's a picture of my 5W IR handheld
I had to put a black metal sheet on the other side sinds it burns everything in it's path.

The camera picks it up as a nice Purple /pink color.

Wow! Are you using an infrared camera or just a normal one that can see infrared somewhat? If that's a normal camera it'd be fantastically bright with an infrared one! Can you see it with your eyes? I can imagine that at that brightness you'd see some form of red glow or something.
How much was that laser, by the way? 5W is definitely packing a punch. I'm surprised (near-)visible lasers come in that power. Thanks for the pictures.

 

[Lazerbeak]

Great thread and pics everybody Your getting good KaPhn8d :beer:

~ LB

 

[BShanahan14rulz]

smeer: I like the indicator LED beam, too!

 

[Smeerworst]

smeer: I like the indicator LED beam, too!

Some people put tape on them, they are really bright!

The blue LED is very bright. Almost as bright as the green dot. Luckily it is very recessed. I need some material to stuff up the hole and block 99% of the blue light

 

[Elite6809]

smeer: I like the indicator LED beam, too!

Judging by the quality of the host there's probably an auxiliary laser dedicated just to that indicator light, haha.