Ok..so I mentioned using a Peltier device for measuring Laser power.
You may or may not know.
This is a pretty neat device..You will find them in A/C heat pumps ..auto air conditioners and portable coolers.,
Lab equipment to heat or cool small items...And DPSS lasers.
Because of the "Peltier effect" by applying a current to the device.. one surface gets hot the other will cool down..
Some are more efficent then others depending how old and what the application was for. And..how many elements they are comprised of.
You will find them in the better DPSS laser units to cool the diode and vanadate or another to heat/cool the KTP.
Also, It may not be known...that they will generate electricity when heated is applied to one side and heatsinked on the other.. ( Seebeck Effect )
This is the basis of my latest Laser power meter.
I have taken a small 3/8 of an inch peltier, found on ebay..
It is the type with the solder coated faces for mounting with the solder to heatsink and the other side to the device under Test.
And mounted it to a small heatsink mounted on a lens holder..
Painted the face of the device with a Black Sharpie.
Setting my Digital Volt Meter to read low AMPS scale ..I can linearly measure
power from any laser , (well, almost).
Now I dont have to care about what wavelength ..much.
well at least in the 488 to 1064 range I can...
It doesnt care either ...we are measuring heat as power.
It does not suffer from the wavelength sensitivity as the other sensors I mentioned before,...
However...It is very slow in making the measurement.
For example: My little 3/8 of an inch mounted I would hit it with 228 mW of red
gave me a reading of 4.00ma and with a multiplication factor of 57
I was able to obtain 228 as was measured on the lasercheck.
I also tried this with Green at a power of 228mW and it also read 4.00.
So...lowering the output to 22.8mw on each gave me .400ma ..
using the multiplication factor again gave me 22.8 as was also read on my
lasercheck.
It seems It is also very linear as well and can measure my 2watt diodes at 808..no problem.
I have been able to measure as low as a milliwatt and as high as 2watts without any problem.(I dont dare go higher until I add a better coating).
I have made a conversion chart for now.
The secret is to keep the heatsink always at the same temp.
Isolating the device from stray air currents and changes will help a lot.
For now , I have it mount to my Optical table lens mount with the peltier enclosed in a lens holder,
However I still need to build a box for it.
Altho I have not tried it yet,
To go Higher in power would require some way of dissapating the heat.
So experimentation with carbon is in order for me...
It does take a few seconds to measure..We are heating up the front side of the peltier. and we need to let the head settle to room temp first.
It is ceramic and thin metal.
Recovery is slow, but hey what do you want for next to nothing.
now..the next thing I plan to do is build a circuit to convert the measurement to
read in volts and this will be equated as Power in Watts. And I can add a range selector too...
Also..it is very sensitive at very low levels to temperatue and stray RF as well as my computer monitor..
I can even wave my hand or soldering iron in front of it,.. and it will see that too!!!
but the amount is very very small...I plan to mount the peltier on another temperature controlled mount..
Stabilized to some degree below or above ambient room temp and enclose it in an aluminum box.
I could also add a thin nichrome wire winding to the mess for calibration... we'll see how that goes...
I did add some by-passing at the test amp as the stray RF is bad here..A local AM station 1 mile away plus my Ham activities makes the meter jump around like no-ones business..
Now , I'm Having fun...
EOT *^_^*
"My signature has been taken, so Insert another here"
http://repairfaq.ece.drexel.edu/sam/laserfaq.htm
*^_^* aka PhiloUHF