help with power checker

my uncle just gave me 2 laser power checkers. They are made to stick down inside copy machines and check the power of the laser. They connect to a regular multimeter, and we were able to find out the mV's of my lasers, but we could not figure out how to find out what the mw's would be. doe's anyone know of a way to check the milliwatts with these? maybe I need to plug them into something else, anyway here are some results and a picture of the checker.

Green
wicked lasers core 5mw-74mV
5mw ebay pen -180mV
pot modded 5mw ebay -402mV
supposed 3W laser... -420mV

Blue
Spartan 1W -473mV
custom 1W -488mV



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You will need to calibrate it against a laser with known output. If you can find a member near by with a LPM you can figure out the mV to mW conversion ratio. Also note that the conversion ratio will be different for each wavelength.

A product that uses a similar set up would be this optical sensor:
>>Click here<<

It uses a table to work out the mW rating from the mV input into the multimeter.

Lastly I don't recommend using this sensor with a >200mw laser. I'm not sure of the materials that are used in the sensor head, but I doubt it has high enough tolerance to deal with anything greater then 200mW... but that's just a guess and a caution.

If those power meters are for copy machines, then they're probably designed solely for IR lasers, not visible light lasers. It probably explains why your numbers are all over the place with the various green lasers you have. Any other wavelengths it picks up might just be some other wavelength the sensor responds to. It may also just be using a photodiode or something that is good only for specific wavelengths not really for a general purpose power meter.

Like the members above stated... it is an optical sensor
and needs calibrating to a known calibrated source to be
of any use as an LPM.

And as stated above you WILL need an optical correction
factor for the optical response of that particular sensor for
each Laser wavelength you want to test.

As it is... you can only compare identical wavelength Lasers
and see which one has a higher output but not how many
milli watts. Once the sensor starts to warm up... you have
probably reached or surpassed its power density (the highest
power level it can safely handle).


Jerry

I can't see it from the picture but it looks like a lasrge area photodiode. Is that circle relatvely dark? In the picture it's reflecting the light.
Photodiodes are wavelength sensitive and as stated need a correction chart. With green lasers the IR leakage gives false measurements results that can't be compensated easily. Depending on the photodiode used it will become nonlinear at a few mw and probably saturate completely at a few tens of mw, maybe 100mW but that's pushing it. Photodiodes aren't ment to measure such high powers without attenuation, they may even be damaged by high power lasers.