Question about back reflection...

[mliptack]

Hello everyone,

It's a very laid back day at work, I'm working for about 9.5 hours and I had one thing to do, and its done already! So I am currently working on some of my projects, one of them relates to lasers. While I was waking up this morning I was thinking about back reflection, it seems like it really becomes an issue when using PBS cubes, but I have to wonder does the offset of the PBS cube pose an issue with reflection from one diode to another?

To clarify, when using one of the razor edge mirror diode setups like arctos uses (although the way those are designed it bypasses this issue...) would the beam from one diode be a hazard to another diode if -say- you only offset the PBS cube slightly? OR is back reflection only an issue with the light emmiting from that same diode?

I hope this makes sense.

Thanks,
Max

[marconi]

Hi max
Back-reflection from the same diode is bad, but any additional photons be it from another diode can be just as dangerous.
So, Yes we want to avoid any of those red photos from going back to the facet of the diode.
Thats why the small offset..just enough to protect the diode some.
So be careful, I've toasted many just being sloppy with the mirrors..

[mliptack]

So could any light be dangerous to diodes? or what properties are damaging? I am trying to get a better grasp on some of the science behind all of equipment we use, which is why I have begun experimenting with diodes, rather than pre-made lasers.

Also, this is off topic to the original post, but is there any easy way to press diodes into an Aixiz style housing... or any housing for that matter? I have been using a drill press, but its a cheap one that is fairly flimsy. The drill press works but I have a tendency to bend the leads of the diode. If anyone has such a device that they use and wouldn't mind describing/uploading some pictures of it would be greatly appreciated!

-Max

[marconi]

Hi Max

Even the premade direct emission diode lasers are prone to this damage.

Since most are run nearly or at maximum output . the facet is what determines its maximum output.
So adding any additional power (reflecting even a few mW) is
going beyond this safe operating parameter and will damage the facet turning that nice laser diode into an LED.

[mliptack]

Ahh, which is the reason why you adjust optics under the maximum output! So in theory, would adjusting the optics with the laser at 50% be safe no matter what? (assuming you are not creating a focal point at the facet)

[marconi]

It is preferable to adjust optics at low power , Yes
That way accidents are less likely to happen.

[mliptack]

You say "less likely" so are they still possible then?

[marconi]

Anything is always possible

But with reasonable care...You should be ok

[CDBEAM]

Hi Chuck,

Well...er...maybe not full speed !!! I am progressing slowly on my RGY projector...but I am approaching the time for mounting the Red MaXYZ duals, Green Lasever, and Dichros.

The progress rate has been that of a receeding Glacier. Many other things going on....but I am enjoying the slow pace....measure 50x...cut once !!!

Anyway...I assume then it is extremely suggested to do mirror alignment with about 2VDC to the blanking input....on both the Red and Green Laser units...?????

Thanx...Bob

[marconi]

Yes, Or ..just enough to make it glow..


Understandable, Projects we like to do sometimes get put on the back burner because life gets in the way