Two types of edge-emitting diode lasers developed by researchers at the Universitat Wurzburg (Wurzburg, Germany) hold promise for monolithic integration with in-plane devices such as waveguides and beamsplitters. Their secret lies in mirrors that are not cleaved but rather fabricated in a way that allows the lasers to remain part of the semiconductor-wafer substrate upon which they are formed.
At each end of the first type of laser made by the researchers, deeply etched trenches define a series of slabs that act as distributed Bragg reflectors (DBRs). The laser itself, of gallium indium arsenide/aluminum gallium arsenide (GaInAs/AlGaAs) and containing a single-quantum-well (SQW) structure, emits at 955 nm. To avoid absorption, the researchers keep the solid portion of the DBR mirrors thin. With proper etching, slabs with smooth sidewalls and aspect ratios of up to 20:1 can be achieved, both essential to the performance of the mirrors.
The second type of laser contains a two-dimensional photonic crystal as one of its mirrors (and an ordinary uncoated cleaved facet as the other). The device is made up of a ridge waveguide formed on a GaInAs/AlGaAs SQW structure; the ridge acts to laterally confine the laser light produced by the SQW. At one end of the ridge, a hexagonal pattern of holes is etched into the underlying SQW structure over an area extending beyond the waveguide and surrounding its end.
John Wallace | Senior Technical Editor (1998-2022)
John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.