Various laser diodes can emit visible light. titanium–sapphire lasers emit mostly in the infrared spectral region, but can be tuned down to. 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. Laser diodes offer high power for their size and produce electrical-power-efficient laser radiation. These gadgets track down wide applications because of their proficiency and minimal size.