In an optical receiver, the photodiode is used to detect the incoming optical signal and convert it into an electrical signal. A laser diode (semiconductor laser) is an electronic component that generates laser light by converting electric current into light using a semiconductor p-n junction. As a light source with excellent directivity and rectilinear propagation that enables easy control of energy, laser diodes are used. The laser diode chip is the small black chip at the front; a photodiode at the back is used to control output power. The anode connection on the right has been accidentally broken by the case cut. Application is going to define the major parameters of a laser diode: wavelength, power, and package style.