A laser diode (LD, also injection laser diode or ILD or semiconductor laser 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. The laser diode is the most common type of laser. Evaluation Board (Resonant Wave Circuit) 3-5. References If an excessive current flows in a laser diode, a large optical output is generated occur and the emitting facet may be damaged.