I was reading about a process called up-conversion mentioned in Robert Boyd's Non-Linear Optics. It is essentially a special case of sum frequency generation (in sum frequency generation, two waves of different frequencies are sent into the crystal, and out comes a wave with a frequency equal to the sum of the two input waves; this is possible due to the non-linear polarization of the crystal). where a weak information-carrying infrared wave is sent in with a strong intensity laser. The two interact, an essentially, the weaker wave is amplified to a higher intensity in the visible region, which is easier for sensing (See image attached for the actual text from the book). I found this very interesting - infrared waves which carry information! It got me thinking: theoretically, we could do 'optics' with 'infrared rays', right? But how do we overcome the problems posed by thermal effects like conduction (and in particular, convection)? Are there special materials out there that can make the use of infrared rays feasible? Can the thermal effects actually be used to our advantage? I wanted to know if anybody here could tell me about experiments or devices which use infrared radiation for information processing. I'm not looking for research papers or anything, I just want a general idea of whether or not such things are attempted, and with what degree of success. Thanks!