ABSTRACT
This chapter aims to developing a basic understanding of the transmitting portion of the optical switch. The transmitting portion of the optical switch is considered the light source and typically takes the form of an infrared light-emitting diode. A P-N junction can be formed in a semiconductor material by doping one region with donor atoms and an adjacent region with acceptor atoms. The P-N junction is characterized by an abrupt change from material containing a majority of positively charged carriers or holes to material containing an excess of negatively charged carriers or electrons. The maximum possible energy of the emitted photons is determined by the band gap energy of the solid in which the P-N junction is formed. The percentage of the current that results in recombinations giving rise to photons of the desired wavelength is a measure of the internal conversion efficiency of the P-N diode.
