Integration of Diffractive Optical Elements with Vertical-Cavity Surface-Emitting Lasers

Abstract

Vertical-cavity surface-emitting lasers (VCSELs) are very desirable sources for a variety of optical system applications. In particular, the inherent planarity of arrays of VCSELs makes them ideal for compact 3-dimensional optical interconnect systems1. Despite smaller beam divergence than edge emitting lasers, spreading of the beam emerging perpendicular to the surface of the VCSEL limits the range of free space transmission, reduces the device density in an array and can introduce cross-talk. Although an external optical system using a separate lens array is a possible solution, the idea may be impractical or expensive due to constraints such as space limitations or the additional need for an optomechanical system to position the lenses. An alternative approach is the integration of high efficiency diffractive optics and VCSELs on a single transparent substrate. Such a compact source is also very attractive for miniature optical instrumentation applications. Integrating diffractive optical elements with substratemitting VCSELs provides a method for manipulating the propagation properties of the exiting beams2. With diffractive structures, a broad range of optical elements can be easily designed and fabricated and high diffraction efficiencies can be achieved with current processing technologies.