Oxygen Gas Sensing with Photothermal Spectroscopy in a Hollow-Core Negative Curvature Fiber

• Main Authors: Yingzhen Hong, Haihong Bao, Wei Jin, Shoulin Jiang, Hoi Lut Ho, Shoufei Gao, Yingying Wang
• Format: Article
• Language: English
• Published: MDPI AG 2020-10-01
• Series: Sensors
• Subjects: optical fiber sensor; oxygen detection; photothermal interferometry; hollow-core fiber
• Online Access: https://www.mdpi.com/1424-8220/20/21/6084
• ISSN: 1424-8220

We demonstrate a compact all-fiber oxygen sensor using photothermal interferometry with a short length (4.3 cm) of hollow-core negative curvature fibers. The hollow-core fiber has double transmission windows covering both visible and near-infrared wavelength regions. Absorption of a pump laser beam at 760 nm produces photothermal phase modulation and a probe Fabry-Perot interferometer operating at 1550 nm is used to detect the phase modulation. With wavelength modulation and first harmonic detection, a limit of detection down to 54 parts per million (ppm) with a 600-s averaging time is achieved, corresponding to a normalized equivalent absorption of 7.7 × 10⁻⁸ cm⁻¹. The oxygen sensor has great potential for in situ detection applications.