Process development, design and characterization of high-finesse micromachined optical Fabry-Perot microcavities

摘要

Micromachined waveguide Fabry-Perot cavities are demonstrated. The devices are fabricated in silicon-on-insulator using a cryogenic dry-etch process, enabling large aspect ratios with high verticality and low surface roughness (≤10 nm). Details of the process development are presented with emphasis on our specific device application. The Fabry-Perot cavities consist of shallow-etched rib waveguides and deep-etched silicon/air distributed Bragg reflector (DBR) mirrors. The high-index-contrast mirrors enable large reflectance with only a few mirror periods. High Q-factor (Q≈27,000) and large finesse (F≈500) were measured. We demonstrate thermo-optic tuning over △λ=6.7 nm and also examine modulation of the cavity (f=150 kHz). Future improvements and application areas of this device are discussed.