Low-Diode Caps (80–120 Diodes): Good for early-stage thinning or small problem areas. High-Diode Caps (250+ Diodes): Full scalp coverage for advanced hair. 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. : 3 Driven by voltage, the doped. Laser diodes, which are capable of converting electrical current into light, are available from Thorlabs with center wavelengths in the 375 - 2000 nm range and output powers from 0. The output wavelength is determined by the different semiconductor compositions and can be set to be in the visible to mid-infrared ranges.