Concave silicon micromirrors for stable hemispherical optical microcavities

Abstract

A detailed study of the fabrication of silicon concave micromirrors for hemispherical microcavities is presented that includes fabrication yield, surface quality, surface roughness, cavity depth, radius of curvature, and the aspect ratio between the cavity depth and radius of curvature. Most importantly, it is shown that much larger cavity depths are possible than previously reported while achieving desirable aspect ratios and nanometer-level roughness. This should result in greater frequency stability and improved insensitivity to fabrication variations for the mode coupling optics. Spectral results for an assembled hemispherical microcavity are presented, demonstrating that high finesse and quality factor are achieved with these micromirrors, F = 1524 and Q = 3.78 × 105, respectively.

A Silicon Optomechanical Accelerometer With High Bandwidth and Sensitivity

“…Two silicon chips are assembled together with a spacer between them to form an optical microcavity. One chip has a concave silicon micromirror [5] and the other has a 10 mg proof mass (3 mm x 3 mm x 0.5 mm) that is suspended with microscale silicon nitride beams. This design combines a highly stable hemispherical cavity, unlike the plane-parallel cavities used in [1,2], with a wafer-scale microfabrication process, unlike the accelerometers described in [3,4].…”