Low-threshold grating-coupled surface-emitting lasers with etch-stop layer for precise grating positioning

The authors discuss the operation of InGaAs/AlGaAs grating-coupled surface-emitting lasers with threshold-current densities as low as 118 A/cm/sup 2/, to the best of our knowledge the lowest reported for a surface emitter. The low threshold-current density is the result of high reflectivity and low absorption gratings in conjunction with a lateral effective refractive index step in the gain section. The gratings were fabricated using electron-beam lithography and chemically assisted ion-beam etching, producing uniform rectangular gratings. A thin etch-stop layer incorporated in the epitaxial structure made it possible to combine precise control of the grating position with a strained-layer SQW-GRINSCH structure for optimum low-threshold currents.>