Work

A continuous-wave quantum cascade laser near 7.5 µ m combined with 2 f -wavelength modulation spectroscopy for trace monitoring of ambient CH 4 concentrations

Year: 2018

Type: article

Abstract: We report a room-temperature continuous-wave (cw) mode-hop-free (MHF) external-cavity quantum cascade laser (EC-QCL) based mid-infrared methane (CH 4 ) sensor operating between 7.5 and 8 µ m in the mid-IR molecular fingerprint region. We utilized the 2 f -wavelength modulation spectroscopy (2 f- WMS) for high sensitive monitoring of atmospheric CH 4 . The strongest interference-free absorption-line in the ν 4 fundamental vibrational band of CH 4 centred at 1327.072 cm −1 was probed to achieve a minimum detection limit of 11 parts-per-billion (ppb) within a relatively small optical pathlength of 1.5 m for an integration time of 272 s. The current cw EC-QCL with MHF frequency tuning capability exploiting the 2 f- WMS detection strategy was subsequently employed for routine monitoring of trace CH 4 levels at the different anthropogenic sources present in the environment. Our findings suggest that the present QCL-based system could lead to the realization of a compact and field-deployable portable sensor for real-time routine monitoring of several other trace gases with high sensitivity and specificity within the tuning range of the laser.

Source: Laser Physics

DOI: 10.1088/1555-6611/aad0d8

Authors: Mithun Pal, Abhijit Maity, Manik Pradhan

Institution: S.N. Bose National Centre for Basic Sciences

Language: English

Topic: Spectroscopy and Laser Applications

Subfield: Spectroscopy

Field: Chemistry

Domain: Physical Sciences

Open Access status: bronze

Funders: Department of Science and Technology, Ministry of Science and Technology, India, Ministry of Earth Sciences, Science and Engineering Research Board

Award: G1312412445