Partial mirror beam splitter for high power laser measurements

[Ed0]

I have read most of the posts here about LPMs but haven't seen any using partial mirrors to measure high power lasers with low power meters. Has anyone here tried it?
The best explanation of how to do it well with glass plates (microscope slides) that I have found is here: Sam's Laser FAQ - Extending the Range of a Laser Power Meter 2

Using two glass plates should reflect about 0.64% of the light so a 100W laser would only supply 640mW to the sensor.

 

[BowtieGuy]

I know I've seen examples of members doing this in the past, but right now the only example I could find was THIS one from a build thread by Blord; maybe it will help.
He mentions this at about pic. #29, BTW, this is a real pic. heavy thread.

 

[paul1598419]

I've seen it done using HR mirrors as well. Most of the light is reflected off, while the small % that gets through is measured.

 

[hakzaw1]

ND filters can also be used..

 

[paul1598419]

That reminds me, I lost an auction for four Edmunds ND filters on eBay. I wasn't that interested in them and they went for about $45.00 with shipping. I think I quit bidding around $38.00 in total. Still a great price for someone who really wanted them

 

[hakzaw1]

WHO KNEW-- that, so soon, our 1W LPMs would be inadequate??

--- try this
If you have lasers w/ known output you can lower power many ways -even the glass lens from dark sunglasses etc. find what % passed and use that to 'calibrate your LPM'
finding on the 'unknown' laser's power-- may be better if the same wavelength is used. A dichro, llke those inside Kasios - has a low % loss- which should be constant as the power goes up. may not be ideal... but much better than=='it pops a match in 3 seconds from 10 feet-- how many mW???
so a ND filter with unknown % splitting can STILL be used..

funniest post I EVER read:
''I can barely feel the laser on my palm or arm...
but do feel it when aimed at my LIP''--wtw?

guess that must be the 'lip-must' test--lol

 

[Light superglue]

Hi,
I have done such type of mesuring when I wanted to check the output from two NUBM44s combined with a PBS into one ~13.5W beam and the sensor of my old powermeter bought in 2007 (not sure but the vendor's nickname was probably Kenom) has limit at 7-8W.
To mesure I have used a NON-polarising beamsplitter as a half mirror and its transparency was ~30%. And some calculations were needed.

Please look at Optics section, thread "Beam splitter/combiner cubes..." somewhere closer to the end.

 

[LSRFAQ]

We professionals use thick wedges to separate the ghost beam from the Fresnel beam..

Much easier then a glass slide..

Steve