NANOFABRICATION OF SUBWAVELENGTH, BINARY, HIGH-EFFICIENCY DIFFRACTIVEOPTICAL-ELEMENTS IN GAAS

A single-etch-step process for the fabrication of high-efficiency diff ractive optical elements is presented. The technique uses subwavelengt h surface relief structures to create a material with an effective ind ex of refraction determined by the fill factor of the binary pattern. Fabrication is performed using electron beam lithography and reactive- ion-beam etching on bulk GaAs, but the process is applicable to any ma terial for which well-controlled etches exist. In this work, we design ed and fabricated a blazed transmission grating for operation at 975 n m. The blazed grating exhibits a diffraction efficiency into the first order of 85% of the transmitted power. (C) 1995 American Vacuum Socie ty.