Surface micro-machined optical coherent detection system with ultra-high sensitivity

Abstract

A surface micro-machined self-homodyne optical coherent detection system is demonstrated. Fabricated on a Silicon chip, such a system comprises a polysilicon membrane as an optical phase modulator, a micro-beamsplitter and two micro-mirrors for beam steering. A three layer polysilicon foundry process provided by MCNC (Mems Center at North Carolina) is used for device fabrication. A signal Max/Min ratio of 22 dB is achieved with this coherent detection system, which in turn offers ultra-high sensitivity in various types of sensing schemes, such as optical refractive index sensing with a minimal detectable index change down to 10 −7, chemical and gas sensing, and laser spectrometry. The optical coherent sensing method is also applicable to the signal readout of inertial sensors, such as in micro-gyroscope technology.