Warning on use of acrylic lens on 445nm at high power

[styropyro]

I have also smoked a lens which burned up my diode.

 

[hakzaw1]

I see no numbers using my hand held microscope--no bar code-- maybe it is under the small plastic piece on the pins-- it can be removed once all the solder is gotten off. Do Not know if it is better left on or removed--somebody will surely tell us.

Sorry these are not better.

I will try again w/ my other camera.

 

[dsholz]

If lasers keep getting more powerful, burning glass optics could become a problem soon. I've had that happen to me with very fine > 5W beams.

 

[hakzaw1]

If lasers keep getting more powerful, burning glass optics could become a problem soon. I've had that happen to me with very fine > 5W beams.

Burning glass ???? that is HOT-- but I have never worked w/ 5W s so i dunno--but that surely takes a lot of heat to burn 'glass' lenses. What nm do you have at 5Ws--?-- I am clueless on Yag CO2 etc--


BTW ------ WELCOME!!

hak

 

[jbtm]

Maybe it will be like CO2 lasers, were the mirrors are specially coated yellow, they are not cheap...who knows, something will come along to fix it...

 

[dsholz]

My experience was either at 532 nm or 1064 nm (if it was IR then it was an even larger power). The beam was very fine too, so the power densities were pretty high. Even then it only caused a small surface burn that cut down on ~30% of the light transmission. We just moved the laser beam a little to the side, to go through a part where it was still undamaged, and everything worked again.

 

[Trevor]

My experience was either at 532 nm or 1064 nm (if it was IR then it was an even larger power). The beam was very fine too, so the power densities were pretty high. Even then it only caused a small surface burn that cut down on ~30% of the light transmission. We just moved the laser beam a little to the side, to go through a part where it was still undamaged, and everything worked again.

If you have access to lasers at that power level, I would hope that you know to use proper optics... :thinking:

-Trevor

 

[blrock]

The first time I used my 10 watt 808nm fiber system I burnt my glass lense. Never thought that was possible. And I burnt several more...along with some stuff on my work desk. 10 watts is just insane. Thankfully I never powered it on until my laser goggles arrived.

And I also put 10 watts focused though a laser pointer DPM. After a BRIGHT green flash the crystal went up in smoke.

 

[dsholz]

twhite828: It was not my job to choose the optics, but I imagine they were reasonable. I do not think rare instances of superficial optical damage are unheard of in a large, complicated, high power system. I was merely trying to contribute by saying that it may become a factor in hobbyist laser devices if powers continue to increase.

 

[Trevor]

twhite828: It was not my job to choose the optics, but I imagine they were reasonable. I do not think rare instances of superficial optical damage are unheard of in a large, complicated, high power system. I was merely trying to contribute by saying that it may become a factor in hobbyist laser devices if powers continue to increase.

I am nothing if not an avid skeptic.

-Trevor

 

[cod4pwns08]

If my 445 laser is running at 600mA with the stock acrylic, will it be destroyed or should it be okay?

 

[aryntha]

If my 445 laser is running at 600mA with the stock acrylic, will it be destroyed or should it be okay?

Okay, the thing you have to understand is this. The phenomenon of "optical darkening" or "photodarkening". It's most important in fiber optics but we're beginning to see it here.

The point of this is: While the lens is clear, it'll continue transmitting your 445nm high powered light. And for a -while-, everything will seem fine. Until a LITTLE bit of darkening starts to happen.

This is when things get interesting. This starts a chain reaction or snowball effect of sorts. You'll be tooling around just fine with the acrylic, so long as its clear. Then, at one point, a few molecules in that lens get a bit too hot, a bit too agitated, and darken.

Then, suddenly, your lens is just a TINY bit darker in one spot than it was. This means it starts to absorb that 445nm light and heat up molecules around it.

Darkening leads to darkening. You get a cascade effect where the darkening accelerates, MORE light is absorbed and turned into heat, less light is transmitted, and so on and so on, until it gets catastrophic and ends in smoke.

The fact of the matter is, this happens very slowly at first, and then speeds up almost exponentially.

So, yes, if you are running an acrylic lens at these high powers, EVEN IF you've been ok for a while, change the thing out for glass, and the proper glass if you can.

I'm currently using a 405-G-1 on my 445, but that's going to move over to my new 8x 405 once I get Aixiz glass from Jayrob and Hak here.

Don't take chances on this. As Dave says, consider it a 'diode cover'. The lens may suddenly start melting, and you do NOT want to be prying that crap off your diode when it does.

 

[hakzaw1]

The above deserves a big +rep. I cannot do it at this time--but maybe you can.

And even if your rep/point count is too low to bump his(thus the blue rather than red for neg or green for pos.)- your comments will get read and the person you +repped will apprecite your input..

The above from Aryntha is a perfect example of giving back to LPF--this advice and explaination has great value to anyone who may have been saved from costly damage to thier diode. Read it and Heed it. For BR and 445 glass is a must!!

Ya'll fed the forum lately?? anything over the goal just helps out next month!!! C'mon now $2 is not a lot to ask....you will never miss it. see this post 'Feed the forum' that guy always cracks me up!!! what a genius!!!!