Applied Electro-Optics

12 Photodetectors

A photodetector device converts incident electromagnetic energy from the optical portion of the spectrum into a useful electrical current. The physical processes involved with this conversion are the reverse of the stimulated emission processes discussed in Chapter 10. Being the first element in the receiver circuit, the photodetector must meet some very rigid performance requirements. It is essentially an open eye on the environment, and as such, can be subjected to a host of changing conditions. Among these requirements are high sensitivity to the particular emission wavelength of the transmitter, fast response, and low noise. It must meet these requirements while being insensitive to changing environmental conditions. These ...