Abstract

In this work, a novel configuration of a photothermal gas sensor is demonstrated. The measured gas sample is delivered to a gas cell placed inside the linear cavity of a 1.55 μm mode-locked fiber laser. The gas refractive index modulation resulting from the excitation by an auxiliary continuous wave laser is efficiently probed by analyzing the phase shift of the self-heterodyne beatnote signal of the mode-locked laser. IQ demodulation combined with Wavelength Modulation Spectroscopy-based signal analysis was employed to optimize and simplify the spectroscopic data acquisition and analysis. A proof-of-concept experiment with detection of carbon dioxide at 2 μm wavelength yielded a noise equivalent absorption of 2.25·10⁻⁷ for 1000 s integration time. The proposed sensor configuration is versatile and can be used to probe any gas molecule, provided an appropriate excitation source is used to induce the photothermal effect.

Sensitive mid-infrared photothermal gas detection enhanced by self-heterodyne harmonic amplification of a mode-locked fiber laser probe

Karol Krzempek
Opt. Express 30(17) 31354-31366 (2022)

Photothermal spectroscopy of CO₂ in an intracavity mode-locked fiber laser configuration

Karol Krzempek, Grzegorz Dudzik, and Krzysztof Abramski
Opt. Express 26(22) 28861-28871 (2018)

Trace gas detection by laser intracavity photothermal spectroscopy

K. H. Fung and H.-B. Lin
Appl. Opt. 25(5) 749-752 (1986)

Part-per-billion level photothermal nitric oxide detection at 5.26 µm using antiresonant hollow-core fiber-based heterodyne interferometry

Karol Krzempek
Opt. Express 29(20) 32568-32579 (2021)

Heterodyne photothermal spectroscopy of methane near 1651 nm inside hollow-core fiber using a bismuth-doped fiber amplifier

Grzegorz Gomolka, Monika Krajewska, Aleksandr M. Khegai, Sergey V. Alyshev, Aleksey S. Lobanov, Sergei V. Firstov, Dariusz Pysz, Grzegorz Stepniewski, Ryszard Buczynski, Mariusz Klimczak, and Michal Nikodem
Appl. Opt. 60(15) C84-C91 (2021)