VCSELs have progressed from laboratory devices to industrial mass production devices in the last few years. A vertical-cavity surface-emitting laser diode (VCSEL) is a semiconductor-based laser diode that emits light or an optical beam vertically from its top surface. The remarkable qualities and properties of this laser type have eventually outperformed Edge Emitting Lasers, which emit light from the side, and Light Emitting Diodes, which emit light from the sides and top. Individual VCSEL emitters are very small, typically around 10 microns in diameter, but most often they are grouped into 2D arrays which collectively generate a much higher output power level.