My heart sank with the mw's

usakicksass · Aug 3, 2008

I was at a birthday party yesterday for a friend. I had my 200mw red laser and was showing it off. I was in a darkened hallway with a bathroom mirror straight ahead and was showing the cool beam it made. Someone asked what would happen if I shined the beam back into the laser. Now I had done this before with my green lasers(to think what could have happened to them) and nothing happened. Just as I got the beam to reflect back into the laser the power went to........ NOTHING! :'( Although I'm not a laser expert I knew what happened. Somehow I put too much energy into the diode.
What was funny was the host of the party grabbed the laser and asked what kind of batteries where in it. I removed the battery and he said he had a whole bunch of AA's. (14500)

Ace82 · Aug 3, 2008

No way!

[waiting_for_physics_geek/] ;D

P.S. I've done that with a few lasers, could it really be how you say? :-/

daguin · Aug 3, 2008

Ace82 said:
No way!

[waiting_for_physics_geek/] ;D

P.S. I've done that with a few lasers, could it really be how you say? :-/

I don't know the physics of, "why?", but I know that reflecting the beam back into the diode can kill it.

However, you do get a nice usable host out of the deal

Peace,
dave

Bionic-Badger · Aug 3, 2008

Well, fortunately, you can replace that diode pretty easily and cheaply. I also hope you were wearing eye protection while demonstrating that laser bouncing off the mirror. If it can fry your diode that quickly, imagine what it can do to your eyes!

IgorT · Aug 3, 2008

Ace82 said:
No way!
P.S. I've done that with a few lasers, could it really be how you say? :-/

Unfortunatelly, yes way..

I killed a diode like that once too.. A perfect reflection could theoretically double the amount of optical flux at the die. A diode doing 200mW after a lens already has to withstand ~240mW. Increase this to 400 and the end facets melt. Once an imperfection developes in the surface, the effect is exponential - COD.

It's pretty much the same as trying to raise the current to reach a higher power. And these diodes are already pushed close to their limits. Sometimes even reflections from a lens can be enough to push them over the limit.

MarioMaster · Aug 3, 2008

IgorT said:
[quote author=Ace82 link=1217779263/0#1 date=1217779632]No way!
P.S. I've done that with a few lasers, could it really be how you say? :-/

Unfortunatelly, yes way..

I killed a diode like that once too.. A perfect reflection could theoretically double the amount of optical flux at the die. A diode doing 200mW after a lens already has to withstand ~240mW. Increase this to 400 and the end facets melt. Once an imperfection developes in the surface, the effect is exponential - COD.

It's pretty much the same as trying to raise the current to reach a higher power. And these diodes are already pushed close to their limits. Sometimes even reflections from a lens can be enough to push them over the limit.[/quote]

Yup, unfortunately back reflection can kill diode lasers fairly easily (doesn't hurt DPSS because the crystals are already receiving the huge output power of the pump diode, so the 20% or so extra that's actually coming out being reflected back in isn't that big of a difference) it's also a much larger risk when the diode is being driven close to its limit to begin with

ixfd64 · Aug 3, 2008

Ugh, that stinks.

I thought those things only happened in cartoons. ;D

MarioMaster · Aug 3, 2008

Yeah, I know a bunch of people on Photon-Lexicon have troubles with Maxyz laser modules and back reflections (those can pop even with 20mW or so reflection from setting up a dichro or galvos, etc)

artix · Aug 3, 2008

When I shine my red laser into my core, the core turns off. But if I turn it on (without my red laser) it is fine green beam :-?

styropyro · Aug 3, 2008

Artix said:
When I shine my red laser into my core, the core turns off. But if I turn it on (without my red laser) it is fine green beam :-?

For the sake of your Core, I wouldn't shine the red laser into the Core anymore. ;D

IgorT · Aug 4, 2008

Artix said:
When I shine my red laser into my core, the core turns off. But if I turn it on (without my red laser) it is fine green beam :-?

Does the core have APC? If so, it turns off, because the APC tries to keep the power constant. Since it's measuring the red, it reduces the power, to reach the pre-set power level but can't, so it shuts down..

If the 200mW red laser used photo diode regulation, it would simply reduce the power to 100mW or so, to keep the total power at the photo diode the same.

This is why, if you have an APC laser, and measure it on certain meters, you have to hold the laser at an angle. Otherwise, the reflection will reduce the power and influence the measurement.

usakicksass · Aug 4, 2008

This is a pic of the beam on white paper. The waves are a new feature.

Had to edit this, sorry for the BIG picture.

Switch · Aug 10, 2008

This is why, if you have an APC laser, and measure it on certain meters, you have to hold the laser at an angle. Otherwise, the reflection will reduce the power and influence the measurement.

But won't happen to dpss lasers right? I mean, the reflection from the sensor head can't really reach the photodiode through the crystals can it? :-/
And I don't know of any red lasers or blurays with APC...

tomcat · Aug 11, 2008

thats dead mate... those waves are the damage to the facet of the diode

i have the same on my dead red i have a huge vertical cleave to one side rather than waves

Ryo · Aug 12, 2008

Considering a 200mW laser can burn through stuff.. shining it back on itself just doesn't seem like good thing to do.. Sorry for your loss.

hydro · Aug 17, 2008

It’s a hard lesson but now we all know.

My heart sank with the mw's

usakicksass

0

Ace82

0

daguin

0

Bionic-Badger

0

IgorT

0

MarioMaster

0

ixfd64

0

MarioMaster

0

artix

0

styropyro

0

IgorT

0

usakicksass

0

Attachments

Switch

0

tomcat

0

Ryo

0

hydro

0

Online statistics

Forum statistics

Share this page