Selecting LED and photodiode

Deepak,

TI has several partner companies that make LEDs and photodiodes and that list of companies is available at http://www.ti.com/lsds/ti/analog/webench/partner-leds.page.  I would try inquiring at these companies to see if they have something available that would suit your needs.

A quick search at big distribution companies (Newark, Digikey) yields photodiodes and LEDs that max out at 1.3um, which would not satisfy your 2-2.5um requirement.

I did some searching for LEDs and photodiodes in the Short Wavelength Infrared spectrum you specified and I found an IEEE paper titled "Low dark current SWIR photodiode with InGaAs/GaAsSb Type II quantum wells grown on InP substrate."  I don't know if that helps with your research but I thought I would mention it.

There are also scintillators for Xray sources that essentially convert Xray radiation into visible light for photodiode measurement; I couldn't find any for scintillators for the infrared spectrum but I didn't do an exhaustive search.  If these exist, they may be an option as well for the photodiode detection side.

Also, while considering your photodiode circuitry, I recommend looking into the DDC product line for measuring the output currents from the photodiodes and performing an analog-to-digital conversion.  The DDC112 has two channels that have the most flexibility with range selection because of the ability to add external capacitors.  The DDC264 has 64 channels with select ranges that is a good choice for dense arrays of photodiodes, and the DDC316 has 16 channels and is intended for significantly faster applications than the DDC112 or the DDC264.  There are other DDC products as well, I encourage you to look at the portfolio.

Jason Bridgmon