A laser with the lasing cavity running vertically through the layers of the semiconductor chip, which is mirrored at the bottom in order to maximize signal emission power at the top surface.VCSELs have capabilities somewhere between LEDs and other lasers. VCSELS have a spectral width somewhere between the two.VCSELs can couple effectively to a multimode fiber (MMF) with a narrower core than LEDs (50 microns versus 62.5 microns), but not as narrow (5
(Vertical Cavity Surface Emitting Laser) Pronounced "vixel." A type of laser diode that emits light from its surface rather than its edge. A VCSEL's circular beam is easy to couple with a fiber, and due to its surface-emission architecture, can be tested on the wafer. VCSELs are also noted for their excellent power efficiency and durability. See laser diode.