Optical Detectors Are Components That Convert Incoming Optical Energy Into Electrical Signals

918 Words Feb 9th, 2016 4 Pages
Optical detectors are components that convert incoming optical energy into electrical signals. Many photonics applications, such as monitoring laser power levels and laser metrology, require the usage of these detectors.1-3 Although there are many different types of optical detectors available covering parts of the electromagnetic spectrum: the ultraviolet, visible and infrared, optical detectors are divided into two main categories: photon and thermal detectors. Photon detectors generate one electron for an incoming photon, which is detected by an electronic circuit, while thermal detectors convert optical energy to heat, which then generates an electrical signal.3
Herein, two types of photodetectors are examined: a PD and a PMT. Although both detectors detect light by converting incident photons to electrical signals, they differ in the way they achieve this. The PD is a p-n junction semiconductor device that generates current when the photodiode absorbs a photon of sufficient energy. This process creates an electron-hole pair through a photoelectric effect. The holes move to the anode while electrons move to the cathode creating a photocurrent. PDs have fair sensitivity and relatively fast response times, but have some limitations due to noise.4 A PMT is a single tube that consists of a photocathode, a series of dynodes, and an anode. Arriving photons strike the photocathode, from which an electron is ejected as a consequence of the photoelectric effect. This electron is…

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