A?laser diode, (LD),?injection laser diode?(ILD), or?diode laser?is a?semiconductor?device similar to a?light-emitting diode?in which a diode pumped directly with electrical current can create?lasing?conditions at the diode’s?junction.?Laser diodes can directly convert electrical energy into light. Driven by voltage, the doped p-n-transition allows for?recombination?of an electron with a?hole. Due to the drop of the electron from a higher energy level to a lower one, radiation, in the form of an emitted photon is generated. This is spontaneous emission. Stimulated emission can be produced when the process is continued and further generate light with the same phase, coherence and wavelength.