Semiconductor lasers are solid-state lasers whose resonant bodies consist of aluminum, gallium and indium compounds. Their light emission is based on their direct band gap, whereas semiconductors such as silicon have no light emission due to their indirect band gap. The wavelength of the light emission, i.e. the color of the light, depends on the photon energy and the composition of the chemical elements.
Semiconductor lasers are based on aluminum and indium compounds. Among these are the AlGaAs laser diode and the AlGaInP laser diode. Others based on indium are the InGaN semiconductor laser and the InGaAs semiconductor laser.
Among semiconductor lasers, the type of light emission distinguishes between surface-emitting and edge-emitting semiconductor lasers. Edge-emitting lasers include the edge-emittinglaser( EEL), in which the emitted light emerges at the edge of the semiconductor. Surface-emitting semiconductor lasers include the laser diode( LD) and the vertical cavity surface emitting laser( VCSEL).
Semiconductor lasers are characterized by a wide wavelength range that can cover visible light as well as near- and mid-wave infrared light. Since they switch for extremely short times, they can be used for light modulation in fiber optic links and can be modulated at gigahertz frequencies. In addition to optical networks, other applications include optical storage, spectroscopy, meteorology, metrology, medical technology and materials processing.