Optoelectronics

36 EE November 1988 Optoelectronics may be defined as the technology that makes use of the interac- tion between photons (small packets of light energy) and electrons. The study and science of this interaction is called photoelectronics, often, particularly in the USA, contracted to photonics. Broadly speaking, optoelectronic prod- ucts may be categorized into sensors (responders to light), emitters (of light), and users (of light), which are often a combination of the first two. Sensors comprise, among others, photo- cells, also called light-dependent resistors (LDR); solar cells; photo- diodes; and phototransistors. Emitters comprise ordinary light bulbs; light-emitting diodes (LED); gas dis- charge tubes; lasers; electroluminescent displays; and cathode ray tubes. Users comprise optocouplers, sometimes called opto-isolators; infra-red alarm and remote control systems; security in- stallations; and metrological devices. Sensors An LDR (photocell) consists of a thin polycrystalli...