determining AR coatings on unknown optics

[Skyko]

I have quite a few optics I pulled from various lasers over the years but didn't classify (bad me).

I also have a huge box of brand new optics of various types/sizes from Coherent, Harold-Johnson, and II-VI. Prisms, PL-CX, PL CC, filters, OC, HR, etc.

These are unfortunately just labeled with job number...and some of the optics have a little arrow on the side, maybe a few numbers that don't seem to mean much to me.


Right now I am really just interested in finding optics that are AR coated for 1064nm that I might want to use on my IPG fiber laser. The only one I think I know would be coated is an optic I just pulled from the fiber coupler on a yag medical laser. It is plano-convex with a 25mm FL and looks like a good start for getting a small spot from my IPG laser.

If I wanted to use some of this other stuff to make a beam expander or use a different FL focus lens, I kind of want to know how it is coated.

Any easy methods?

[als1980]

I have been looking for the same info everywhere. There doesn't seem to be an easy answer vs using a spectrometer to measure absorbance vs reflectance. If anyone has a better method to determine lens coatings I want to know. Lol! Skyco, I have a bunch of lens , let me know what you need for that IPG I may be able to help.

[Skyko]

Thanks! First I need to test out the laser and make sure it is performing to spec before I keep it. Then I will want to get the smallest spot size possible since I would like to do micromachining and the laser is kind of small for this. If I can focus down to 10 microns or so I would be able to do what I want. From what I have read and the quality of the beam from these lasers that could be possible with the right optics. The data sheet says the beam comes out at 6mm min 9mm max...sounds like it is already being run through a beam expander/collimator?

[als1980]

Most likely a small. One. If you figure out what you need I probly have it. I have wayyyy to many optics right now. Many that I can't fully identify, all brand new.

[mixedgas]

A Laser at a known wavelength and a sensitive power meter works for a close approximation. Of course you need a laser at EACH wavelength you want to measure. You just determine the transmission and reflection while placing the optic in the beam. Otherwise this requires a spectrophotometer, or a broadband source and something like a Ocean Optics USB spectrometer.
Steve

[Skyko]

you would have to make sure that placing the optic in the beam would not alter the way the beam hits the power meter head (unless it is thermal...but I don't see getting an accurate reading with a lower power source on a thermal head). If the optic was a short focal length lens, would the focused spot give a different reading on a photodiode type of detector vs an unfocused spot of the same power level? I should know this but haven't looked it up...maybe higher power density frees up more charge carriers or something in the pn junction...

[mixedgas]

A large photodiode with a thin ground glass or ceramic wafer is the norm. Done properly they are very much angle and diameter insensitive.

Steve