A Hybrid MEMS–Fiber Optic Tunable Fabry–Perot Filter

This paper describes a bulk-micromachined electrostatically tunable Fabry-Perot interferometric filter. The device is a hybrid optical filter combining fiber optics and microelectromechanical systems (MEMS) technologies. The static mirror is a Bragg grating mirror built on the end face of an optical fiber that is integrated with a MEMS device, which includes the tunable gold-coated mirror. The MEMS device is fabricated in ¿100¿-oriented silicon wafers using modified and optimized batch MEMS processes. A two-stage approach was used to achieve high finesse (F) and broad tunability simultaneously. In the first stage, actuator issues and mirror structural defects were corrected for by optimizing the fabrication-process parameters. In this stage, near-theoretical performance has been achieved with a pure Si MEMS tunable etalon. In stage two, optical fibers with dielectric stack mirrors from Micron Optics, Inc. have been integrated with the MEMS devices to form tunable cavities. The device insertion loss was below 15 dB and was mostly attributed to absorption losses in the gold coating. We measured a pass bandwidth of around 0.54 nm and a tuning range of nearly 120 nm resulting in an F of over 220.