[Laser] Re: MORE XE2AT PART 2 (Art)

[Art]

There is a company that makes wavelength dependent photodiodes, but I can't 
remember the company's name. The diodes nearly eliminate the need for 
optical passband filters and the loss they create.

The responsivity is actually better than the .45 A per watt that standard 
photodiodes have too...so they are actually more sensitive due to the 
physical construction of the part. I think the diodes peak at 850 nm, have 
the same noise current, but the responsivity increases to .55 or .6 A per 
watt at 850 nm.

Low cost red filters are easy enough to find, but sharp filters with low 
loss are more pricey.

Art



At 10:43 AM 2/11/04, you wrote:
>I was able to attenuate the ambient light by placing an optical filter in
>front of the photodiode. For "red" LASER's, I found that the red plastic
>covers that were used over LED numeric displays work reasonably well, and
>can be salvaged from old equipment.
>walt