Surface-micromachined mirrors for laser-beam positioning

Abstract

Actuated surface-micromachined polysilicon micromirrors for laser-beam positioning have been designed and fabricated. Two types of beam-steering mirrors are discussed which use microhinge technology to achieve the required vertical dimensions and functionality. One mirror, intended for precise beam positioning as needed in optical alignment, is actuated by linear microvibromotors. The other mirror is appropriate for laser-beam scanning and uses electrostatic comb-drive actuators. Four layers of polycrystalline silicon are micromachined to form these devices. Environmental stress testing carried out on the beam-positioning mirror has shown its structure to be relatively insensitive to vibrations below 60 kHz. Further testing has shown negligible changes in mirror position for temperatures varying between 25 and 200°C, and stability under the stress of laser irradiation of 375 mW at 1.06 μm wavelength.