Heterodyne-enhanced Faraday rotation spectrometer

作者：Yin Wang, Michał Nikodem, Jake D. Hoyne, Gerard Wysocki · 发表于：Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 年份：2011 · DOI：10.1117/12.908593 · 被引用次数：7 · 研究领域：Cold Atom Physics and Bose-Einstein Condensates、Mechanical and Optical Resonators、Quantum optics and atomic interactions

A novel heterodyne-enhanced Faraday rotation spectroscopic (H-FRS) system for trace gas detection of nitric oxide (NO) is demonstrated. The system is based on a quantum cascade laser emitting at ~5.2 μm and a mercury cadmium telluride photodetector (both thermoelectrically cooled). The heterodyne detection is performed at 30MHz, where the laser relative intensity noise is significantly smaller than at low frequencies. With an implementation of active interferometer stabilization technique, the current system shows total noise level that is only 5.4 times above the fundamental shot-noise limit and the Faraday rotation angle sensitivity of 2.6 × 10 -8 rad/√Hz. The NO detection limit of 30.7 ppb-v/√Hz was achieved for the R(8.5)e NO transition using 100 Gauss magnetic field and 0.15 m optical path length.