Fundamentals of Optical Detectors

Abstract

The photodetection devices used in biophotonic disciplines are semiconductor-based pin and avalanche photodiodes, photomultiplier tubes, silicon photomultipliers, and optical detector arrays. The photodetectors can be either single-channel elements or multichannel devices. With a single-channel element only one spectral channel in a biophotonic setup can be monitored at any instance in time. However, multichannel devices can measure multiple spectral channels simultaneously or observe spatial channels individually in different time sequences. Associated with photodetection setups is the need for optical filters, optical couplers, and optical circulators. Optical filters selectively transmit light in one or more specific bands of wavelengths. Optical couplers split or combine two or more light streams, tap off a small portion of optical power for monitoring purposes, or transfer a selective range of optical power. An optical circulator is a non-reciprocal multi-port device that directs light sequentially from port to port in only one direction.