InGaAs/AlGaAs semiconductor lasers come in threetypes: VCSELs and two types of EELs. The VCSEL, asits name implies, emits vertically, normal to the planeof the device, owing to cavity mirrors grown withinthe epitaxial material itself. The VCSEL’s circular beamhas a numerical aperture (NA) of roughly 0.2, or a fullangle of approximately 25 degrees.
