Number 217 (Story #3), March 10, 1995 by Phillip F. Schewe and Ben Stein VERTICAL CAVITY SURFACE EMITTING LASERS (VCSELs) are now able to work efficiently at visible and far-infrared wavelengths. VCSELs emit light vertically out of the plane of the laser's active medium rather than horizontally from one of its edges. Also, because one of the laser's reflective mirrors consists of disk-shaped AlAs/GaAs layers, the emergent laser beam has a circular profile, lessening the need for focusing elements. Arrays of such lasers could be used in displays, short-distance communications between microchips, and possibly in long- distance transmissions over fibers. Previously successful at getting VCSELs to emit at near- infrared wavelengths (a few months ago Motorola started selling the first commercial devices employing VCSELs), researchers at Sandia have only recently overcome obstacles (such as a mismatch between neighboring semiconductor layers) to produce VCSELs that emit in the visible (red) range with nearly the efficiency as near-infrared devices. At far-infrared wavelengths (important for transmission in fibers) a Santa Barbara group has produced a VCSEL that emits at 1.52 microns. Furthermore, this device has set a record for the lowest room- temperature threshold current density for a laser (Dubravko Babic et al., Applied Physics Letters, 27 February 1995.) This device does not yet operate in a continuous mode, which is desirable for commercial use. Finally, a company in Minnesota, APA Optics, has made the first VCSEL to operate at ultraviolet wavelengths. (Science, 24 February 1995.)