LOW-THRESHOLD GRATING-COUPLED SURFACE-EMITTING LASERS WITH ETCH-STOP LAYER FOR PRECISE GRATING POSITIONING

We report on the operation of InGaAs/AlGaAs grating-coupled surface-em itting lasers with threshold-current densities as low as 118 A/cm2, to the best of our knowledge the lowest reported for a surface emitter. The low threshold-current density is the result of high reflectivity a nd low absorption gratings in conjunction with a lateral effective ref ractive index step in the gain section. The gratings were fabricated u sing electron-beam lithography and chemically assisted ion-beam etchin g, producing uniform rectangular gratings. A thin etch-stop layer inco rporated in the epitaxial structure made it possible to combine precis e control of the grating position with a strained-layer SQW-GRINSCH st ructure for optimum low-threshold currents.