Optical resonator formed with etched silicon micromirrors

Abstract

The applications for optical resonators are manifold, ranging from laser resonators and filters to optical sensors based on resonators, such as optical gyroscopes. A concept of a miniaturized optical gyroscope has been developed. To realize a gyroscope of this sort, the assembly and precision alignment of the optical microcomponents to form a triangular cavity is crucial. In order to detect the rotation rate, the laser beam must circulate many times and not leave the resonator due to small misalignments. Therefore, the assembly of a miniaturized passive free space triangular ring resonator, in which the light can circulate by reflections by three mirrors, is investigated. To utilize the inherent alignments of crystal planes, two of the mirrors are realized by micromanufacturing within the same silicon crystal using wet etching, resulting in very perfect {111} facets. To further increase the reflectivity of the mirrors, different kinds of coatings are tested. With these two perfectly aligned mirrors, the resonator assembly challenge reduces to a three-degree of freedom alignment of a third mirror, in which a well-designed adjustable spacer is developed. Resonances with the etched {111} micromirrors in a linear cavity setup as well as in a triangular ring cavity setup have already been demonstrated.