VCSEL is a semiconductor micro-laser diode that emits light in a cylindrical beam, vertically from the surface of a fabricated wafer, and offers significant advantages when compared to the edge-emitting lasers currently used in the majority of fiber optical communication systems. When compared with edge0emitters, VCSELs offer lower threshold currents, low-divergence circuilar output beams, higher direct modulation speed, longitudinal single mode emission, ease of integration to form 2-D arrays and higher coupling efficiency into optical fiber. However, high fiber-coupling efficiencies are only reached at low optical powers, because with increasing output power, higher order transverse modes are supported by the cavity. In general, the complex transverse modal behavior of VCSELs at high pump rates is a major drawback for many practical applications. The modal behavior, just like most of the other key porperties of the VCSELs, depends strongly on the confinement mechanism. Despite many of their inherent advantages over its rivals VCSELs still suffer from many inadequacies. Most prominent are 'limited power' and lack of 'modal purity'. These unresolved issues have compelled the VCSEL to enjoy only 10% share of the whole semiconductor laser market.
|Original language||English (US)|
|State||Published - Jan 9 2004|