[Laser] Re : Strange effect

[Tim Toast]

Dave,
That is probably the reason. Without looking it up, that seems to ring a bell somewhere 
about silicon emitting in the deep IR. I hadn't fully realized till now that all LEDs might not 
have the near same detect + emit wavelengths. It makes me wonder how some of the 
other LED compositions  wavelengths are arranged too. I think i've read, in the 
UKnanowaves group, they had used green and blue LEDs in their (single led type) 
transceivers with good results. Those both may use gallium arsenide though, i don't 
know. I was thinking the blue LEDs used a nitride based construction.
 
Yves, 
You may be able to tell whether the pyrodetector is seeing the actual 1.1 micron 
radiation or the 10 micron heat, by turning the silicon detector on and off rapidly. 
If the pyrodetector is just seeing the heat generated, then the silicon detector should 
continue to "glow" for a short time after it is turned off (as it cools off) rather than a 
crisp instant on/off responce.. It may be sensitive to a combination of both even.
 
-toast