Repetitively Mode-Locked Cavity-Enhanced Absorption Spectroscopy (RML-CEAS) for Near-Infrared Gas Sensing

Abstract

A Pound-Drever-Hall (PDH)-based mode-locked cavity-enhanced sensor system was developed using a distributed feedback diode laser centered at 1.53 µm as the laser source. Laser temperature scanning, bias control of the piezoelectric ceramic transducer (PZT) and proportional-integral-derivative (PID) feedback control of diode laser current were used to repetitively lock the laser modes to the cavity modes. A gas absorption spectrum was obtained by using a series of absorption data from the discrete mode-locked points. The 15 cm-long Fabry-Perot cavity was sealed using an enclosure with an inlet and outlet for gas pumping and a PZT for cavity length tuning. The performance of the sensor system was evaluated by conducting water vapor measurements. A linear relationship was observed between the measured absorption signal amplitude and the H2O concentration. A minimum detectable absorption coefficient of 1.5 × 10–8 cm–1 was achieved with an averaging time of 700 s. This technique can also be used for the detection of other trace gas species by targeting the corresponding gas absorption line.

Near infrared ammonia sensing system based on on‐axis cavity‐enhanced absorption spectroscopy using board‐level mode‐locked circuit

“…A minimum detection limit of 104.9 ppmv for an average time of 50 s was attained by observing the absorption of water vapor. 18 In 2020, He et al further demonstrated a formaldehyde (H 2 CO) detection system involving a continuous-wave distributed feedback interband cascade laser with a wavelength of 3.6 μm and an assembly F-P cavity with 20 m effective optical path. A minimum detection limit of 5.8 ppbv for an average time of 30 s was attained by observing the absorption of H 2 CO. 19 ML-CEAS has promising potential for gas detection application, however, there are limitations to high-precision but expensive and bulky PDH mode-locking devices.…”

“…In 2017, He et al locked a distributed feedback laser diode with a central wavelength of 1.53 μm to the fundamental mode (TEM 00 mode) of an F‐P cavity with an optical path of 49.7 m based on the Pound–Drever–Hall (PDH) technique. A minimum detection limit of 104.9 ppmv for an average time of 50 s was attained by observing the absorption of water vapor 18 . In 2020, He et al further demonstrated a formaldehyde (H 2 CO) detection system involving a continuous‐wave distributed feedback interband cascade laser with a wavelength of 3.6 μm and an assembly F‐P cavity with 20 m effective optical path.…”

Toroidal Dipole-Induced Photocurrent Enhancement in Si Nanodisk Hexagonal Array below the Band Gap

“…Near infrared (NIR) light often defined in the wavelength range of 800 to 2500 nm is transparent in many materials and has been widely used in optical telecommunication, − face recognition, , autonomous driving, gas sensing, bioimaging, − and so on. Conventional silicon (Si) photodetectors have sensitivity up to ∼1100 nm, and longer wavelength ranges are covered by narrow band gap semiconductors such as InGaAs, InP, and Ge.…”

Double-range near-infrared acetylene detection using a dual spot-ring Herriott cell (DSR-HC)

“…A multi-pass gas cell [10] and a high-fineness cavity [11] are two kinds of gas absorption approaches for enhancing sensitivity based on different principles, which are widely used in TDLAS based gas sensor systems. A multi-pass cell realized by symmetric spherical mirrors in a Herriott cell configuration is commonly used for trace-gas detection [12][13][14], in Raman spectroscopy [15][16] and atmospheric in situ instrumentation [17][18][19].…”