Oxygen detection based on Faraday modulation spectroscopy and wavelength modulation spectroscopy: A comparison

We proposed a near‐infrared gas sensing system based on mode‐locked cavity‐enhanced absorption spectroscopy. A distributed feedback fiber laser (DFB‐FL) with a central wavelength of 1550 nm was employed as the light source, coupling with a Fabry–Perot (F‐P) cavity with an effective optical path length of 42.7 m served as the gas cell. By utilizing a homemade mode‐locked electric circuit and Pound–Drever–Hall (PDH) technique, the mode‐locking between the DFB‐FL and F‐P cavity was achieved with long‐term fluctuation of 3.2%. System performance was verified using ammonia as the analyte gas with a target line at 1550.17 nm. Allan variance analysis revealed that the minimum detection limit was 15.8 ppm with an averaging time of 216 s, corresponding to an absorption coefficient of 2.3 × 10−7 cm−1.

Section: Introductionmentioning

confidence: 99%

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

Zhu,

Guan,

et al. 2024

“…Different spectroscopy techniques play an important role in the field of sensing. [1][2][3][4][5][6][7][8][9][10][11] Laser absorption spectroscopy, based on Lambert-Beer law, provides information about the type and concentration of gases by measuring the wavelength and intensity of absorption lines. 12 This detection method is less affected by cross-sensitivity among gas components compared to nonoptical methods.…”

Section: Introductionmentioning

confidence: 99%

Theoretical and experimental investigation of chalcogenide suspended waveguide gas sensor

Huang,

Wang,

et al. 2023

To address the issues of low ratio of evanescent field (γ) and high reflectivity between waveguide cross‐section and gas for the mid‐infrared waveguide sensors, we propose a chalcogenide (ChG) suspended waveguide with Ge28Sb12Se60 as the core layer and silica (SiO2) as the buffer layer. The SiO2 beneath the waveguide core ridge structure is removed to create suspended structure. The waveguide sensing performance is obtained using a 10% methane (CH4) sample. The fabricated waveguide exhibits a γ of 112%, which is a 10% improvement compared to a free‐space optical sensor with the same optical path length. The good agreement between the theoretical and experimental results of γ confirms the reliability of our theoretical investigation approach. The influences of fabrication error, environmental temperature, and pressure on sensing performances are discussed. This work provides theoretical guidance for designing waveguide structures with large γ, contributing to the further enhancement of on‐chip sensor performance.

“…5 As early as 1977, using laser spectroscopy to deduce 14C/C has been proposed, which leverages the measurement of 14 CO 2 spectra. 6,7 This approach [8][9][10][11][12][13][14][15][16][17] offers advantages such as real-time detection, transportability, and inexpensiveness. In the past decade, beneficial from the development and commercialization of optical components at mid-infrared (MIR), several spectroscopic setups for 14 C detection have been built and some astonishing results have been reported.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic detection of radiocarbon dioxide based on optical feedback linear cavity enhanced absorption spectroscopy

Jiao,

Gao,

Yang

et al. 2023

Spectroscopic detection of radiocarbon dioxide (14CO2) offers several advantages, including real‐time detection, on‐site measurement capability, and ease of operation. Here, we propose a novel 14CO2 detection technique that utilizes optical feedback linear cavity enhanced absorption spectroscopy. The feedback phase is actively compensated by adjusting the light path length. The combination of cavity‐based technique and optical feedback enables the recording of stable and enhanced 14CO2 spectra. Through Allan deviation analysis, a minimal detectable 14CO2 concentration of 3.5 parts‐per‐trillion is achieved. This technique has the potential to contribute to the monitoring of the radiocarbon emissions in the air of nuclear power plants.