ABSTRACT
Since the first report of vertical cavity surface emitting lasers (VCSELs) in 1978 [1], their unique attributes and advantages have generated both research and commercial interest worldwide. As their name indicates, VCSELs emit light perpendicular, rather than parallel, to the wafer surface. This topological distinction is enabled through the use of distributed Bragg reflector (DBR) mirrors for longitudinal optical confinement. Thus a fundamental difference
between VCSELs and conventional edge emitting lasers is the elimination of facet mirrors fabricated by either cleaving or dry etching [2]. Consequently VCSELs possess several inherent advantages over edge emitting lasers including: (i) a low divergence circular laser beam, (ii) the requirement of only standard fabrication processes such as used in silicon integrated circuit fabrication, (iii) the capability of wafer level testing before packaging, and (iv) the fabrication of dense 2-dimensional laser arrays. However for both edge emitting lasers and VCSELs, transverse confinement of both electrons and photons is still required to define the laser active volume.
