  Silicon optics with wide bandwidth anti-reflection (AR) coatings, made of
multi-layer textured silicon surfaces, are developed for millimeter and
submillimeter wavelengths. Single and double layer AR coatings were designed
for an optimal transmission centered on 250 GHz, and fabricated using the DRIE
(Deep Reaction Ion Etching) technique. Tests of high resistivity silicon wafers
with single-layer coatings between 75 GHz and 330 GHz are presented and
compared with the simulations.
