High-Sensitivity Phase Detection of Reflection-Type Guided-Mode Resonance Sensor Based on Rotating Azimuth Angle Using a Heterodyne Interferometer

A high-sensitivity phase-detection system is proposed for a reflection-type guided-mode resonance (GMR) sensor, which achieves the resonance condition by rotating the azimuth angle and utilizes an electro-optic (EO) heterodyne interferometer. By rotating the GMR sensor azimuthally, the direction of the reflected light can be maintained in reflection-type detection, and the optical system can be compactly constructed because the light-tracking rotation stage is not required. The phase-detection sensitivity can be enhanced in this common-path EO heterodyne interferometer by rotating the analyzer in front of the photodetector; therefore, this system can achieve both a high sensitivity and low limit of detection. Numerical and experimental results of the reflectivity and phase response curves versus the azimuth angle were compared. The proposed system was used to perform gas sensing, and its detection sensitivity and limit were 3.73 x 10(4) deg/RIU and 2.68 x 10(-7) RIU, respectively.