Pitch-variable blazed grating consisting of freestanding silicon beams

Theoretical analysis is presented for a pitch-variable blazed grating which consists of freestanding silicon beams. The pitch-variable blazed grating is implemented by combining silicon-on-insulator (SOI) technology with microelectronicmechanical system (MEMS) technology. The whole device is fabricated on a 10μm silicon device layer to guarantee sufficient stiffness. The 4-level blazed surface profile is realized by combining a two-mask process with fast atom beam etching. Electrostatic combdrive microactuators with double folded springs are proposed to stretch the freestanding grating beams. In association with reactive ion etching and vapor HF release, the freestanding grating beams and the microactuators are obtained, and a Cr/Au film is deposited onto the blazed grating surfaces by a protective mask process to improve the diffracted power. Mechanical response and diffraction efficiency of fabricated devices are characterized, and the experimental results indicate that the fabricated 4level blazed gratings extend both the tuning range and the diffraction efficiency of the 1^st diffraction order of present MEMS diffraction gratings.