{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,9]],"date-time":"2026-01-09T18:55:04Z","timestamp":1767984904595,"version":"3.49.0"},"reference-count":22,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2023,1,1]],"date-time":"2023-01-01T00:00:00Z","timestamp":1672531200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The line width of different line shapes is a very important parameter in absorption spectroscopy sensing techniques. Based on the high sensitivity and low noise properties of wavelength modulation spectroscopy, we report a novel line width measurement method. After theoretically proving the relationship between line width, modulation amplitude and the amplitude of the second harmonic at the center frequency, the absorption lines of CH4 near 6046.96 cm\u22121 and CO2 4989.97 cm\u22121 were chosen for simulation, and the relative errors of the line width between our method and theoretical data were kept at about 1%. A distributed feedback laser diode operating near 1653 nm with three different concentrations of CH4 was used for experimental validation, and the results were consistent with the numerical simulation. Additionally, since only the peaks of second harmonic need to be measured, the advantages of wavelength modulation can be utilized while reducing the difficulty of data acquisition.<\/jats:p>","DOI":"10.3390\/s23010476","type":"journal-article","created":{"date-parts":[[2023,1,2]],"date-time":"2023-01-02T03:50:32Z","timestamp":1672631432000},"page":"476","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["A Width Measurement Method of Line Shape Based on Second Harmonic Peak and Modulation Amplitude"],"prefix":"10.3390","volume":"23","author":[{"given":"Shan","family":"Lin","sequence":"first","affiliation":[{"name":"School of Information Science and Engineering and Shandong Provincial Key Laboratory of Laser Technology and Application, Shandong University, Qingdao 266200, China"},{"name":"Key Laboratory of Laser and Infrared System of Ministry of Education, Shandong University, Qingdao 266200, China"}]},{"given":"Jun","family":"Chang","sequence":"additional","affiliation":[{"name":"School of Information Science and Engineering and Shandong Provincial Key Laboratory of Laser Technology and Application, Shandong University, Qingdao 266200, China"}]},{"given":"Jiachen","family":"Sun","sequence":"additional","affiliation":[{"name":"School of Information Science and Engineering and Shandong Provincial Key Laboratory of Laser Technology and Application, Shandong University, Qingdao 266200, China"}]},{"given":"Zihan","family":"Wang","sequence":"additional","affiliation":[{"name":"School of Information Science and Engineering and Shandong Provincial Key Laboratory of Laser Technology and Application, Shandong University, Qingdao 266200, China"}]},{"given":"Minghui","family":"Mao","sequence":"additional","affiliation":[{"name":"School of Information Science and Engineering and Shandong Provincial Key Laboratory of Laser Technology and Application, Shandong University, Qingdao 266200, China"},{"name":"Key Laboratory of Laser and Infrared System of Ministry of Education, Shandong University, Qingdao 266200, China"}]}],"member":"1968","published-online":{"date-parts":[[2023,1,1]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"37879","DOI":"10.1364\/OE.411278","article-title":"Spatially and Temporally Resolved Temperature Measurements in Counterflow Flames Using a Single Interband Cascade Laser","volume":"28","author":"Wen","year":"2020","journal-title":"Opt. 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