Current Projects

Laser Diode Structures

Vertical Cavity Ring Laser

Vertical cavity lasers are a hot topic in optoelectronics because of their many advantages over edge-emitting types. They are highly coherent, and surface emitting, which means no more unpleasant cleaving and great easing of alignment procedures, as well as the greater ease of integration with electronic devices on the same chip. We have designed a vertical cavity laser that is actually a ring laser (rather than a conventional Fabry-Perot laser), [8] which allows for coupling to adjacent devices as well as surface emission. This allows a small part of the beam from one laser to be injected into an adjacent laser, for injection locking. By arranging a string of these, one can build a phased-locked surface emitting array for high power applications.

Coherent Laser Arrays

Laser diode arrays can be either coherent (all elements in phase, for applications in which beam quality is an issue) or incoherent (to get huge amounts of power out of a laser without blasting the facets off). Most current vertical cavity arrays are incoherent because of the difficulty of phaselocking two of these adjacent devices. Edge-emitting phase-locked arrays are commercially available, and we have looked into the possibility of using these for holographic optical interconnections.[9] To write a hologram, one needs two (or more) beams that are mutually coherent, and this is usually done by using one laser and a beamsplitter to pick off some of the energy. The beamsplitter produces a second beam coherent with the first. Bulk optics are to be avoided, however, because of size and alignment problems, so we want to use the mutually coherent phase locked elements of a phased diode array as the sources in an optical interconnection. The individual elements can be selected using monolithically integrated electroabsorption modulators.