TY - JOUR
T1 - Heterodyne interferometric photothermal spectroscopy for gas detection in a hollow-core fiber
AU - YAO, CHENYU
AU - Gao, Shoufei
AU - YINGYING, WANG
AU - Jin, Wei
AU - REN, WEI
N1 - This work was supported by Natural Science Foundation of Guangdong Province, China (2019A1515011372), General Research Fund (14206317, 14209220) from the University Grants Committee, and Seed Project (ITS/242/19) from the Innovation and Technology Commission of Hong Kong SAR, China. Chenyu Yao also acknowledges the funding support by the Research Talent Hub (PiH/365/20) from the Innovation and Technology Commission of Hong Kong SAR, China.
References
PY - 2021/11
Y1 - 2021/11
N2 - Photothermal spectroscopy with the optical pump-probe configuration has been used for sensitive gas detection in hollow-core fibers. In this study, we demonstrate a new method of heterodyne interferometric photothermal gas sensing with a simplified sensor design and enhanced sensor stability. As a proof-of-principle, we used an interband cascade pump laser at 3.6 μm for nitrous oxide (N2O) detection in a hollow-core anti-resonant fiber (HC-ARF). A Mach-Zehnder interferometer (MZI) with a 1.5 μm near-infrared probe laser was implemented to measure the photothermal-induced refractive index change inside the HC-ARF. The probe laser was split into two beams, one transmitted through the HC-ARF and one frequency-shifted by using an acoustic-optic modulator. Both beams were recombined to generate a beat note signal, which was then demodulated by two cascaded lock-in amplifiers to extract the photothermal signal. Based on the first harmonic detection of wavelength modulation, we achieved a normalized noise equivalent absorption (NNEA) coefficient of 7.7×10−9 cm-1WHz-1/2. Compared to conventional photothermal gas sensors with the MZI configuration, our new detection scheme eliminates the sophisticated opto-mechanical stabilization system and exhibits the intrinsic immunity to the power fluctuation of the probe laser.
AB - Photothermal spectroscopy with the optical pump-probe configuration has been used for sensitive gas detection in hollow-core fibers. In this study, we demonstrate a new method of heterodyne interferometric photothermal gas sensing with a simplified sensor design and enhanced sensor stability. As a proof-of-principle, we used an interband cascade pump laser at 3.6 μm for nitrous oxide (N2O) detection in a hollow-core anti-resonant fiber (HC-ARF). A Mach-Zehnder interferometer (MZI) with a 1.5 μm near-infrared probe laser was implemented to measure the photothermal-induced refractive index change inside the HC-ARF. The probe laser was split into two beams, one transmitted through the HC-ARF and one frequency-shifted by using an acoustic-optic modulator. Both beams were recombined to generate a beat note signal, which was then demodulated by two cascaded lock-in amplifiers to extract the photothermal signal. Based on the first harmonic detection of wavelength modulation, we achieved a normalized noise equivalent absorption (NNEA) coefficient of 7.7×10−9 cm-1WHz-1/2. Compared to conventional photothermal gas sensors with the MZI configuration, our new detection scheme eliminates the sophisticated opto-mechanical stabilization system and exhibits the intrinsic immunity to the power fluctuation of the probe laser.
U2 - 10.1016/j.snb.2021.130528
DO - 10.1016/j.snb.2021.130528
M3 - Journal article
SN - 0925-4005
VL - 346
JO - Sensors and Actuators B: Chemical
JF - Sensors and Actuators B: Chemical
M1 - 130528
ER -