Injection LaserDiode( ILD) is a semiconductor laser diode because it uses a specially doped junction between a P layer and an N layer for coherent light radiation.
Doping causes photons to be emitted when voltage is applied, producing the light radiation. The laser effect is produced by a feedback loop.
The injection laser diode operates in the forward direction. Its characteristic curve shows a sharp kink at about 300 mA, marking the transition between normal light radiation and the laser effect. After this kink, the light emission increases much more steeply than before the kink.