Intrinsic Spectral Resolution Limitations of QEPAS Sensors for Fast and Broad Wavelength Tuning
Quartz-enhanced photoacoustic sensing is a promising method for low-concentration trace-gas monitoring due to the resonant signal enhancement provided by a high-Q quartz tuning fork. However, quartz-enhanced photoacoustic spectroscopy (QEPAS) is associated with a relatively slow acoustic decay, whic...
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MDPI AG
2020-08-01
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| Series: | Sensors |
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| Online Access: | https://www.mdpi.com/1424-8220/20/17/4725 |
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| author | Jesper B. Christensen Lasse Høgstedt Søren M. M. Friis Jui-Yu Lai Ming-Hsien Chou David Balslev-Harder Jan C. Petersen Mikael Lassen |
| author_facet | Jesper B. Christensen Lasse Høgstedt Søren M. M. Friis Jui-Yu Lai Ming-Hsien Chou David Balslev-Harder Jan C. Petersen Mikael Lassen |
| author_sort | Jesper B. Christensen |
| collection | DOAJ |
| description | Quartz-enhanced photoacoustic sensing is a promising method for low-concentration trace-gas monitoring due to the resonant signal enhancement provided by a high-Q quartz tuning fork. However, quartz-enhanced photoacoustic spectroscopy (QEPAS) is associated with a relatively slow acoustic decay, which results in a reduced spectral resolution and signal-to-noise ratio as the wavelength tuning rate is increased. In this work, we investigate the influence of wavelength scan rate on the spectral resolution and signal-to-noise ratio of QEPAS sensors. We demonstrate the acquisition of photoacoustic spectra from 3.1 <inline-formula><math display="inline"><semantics><mi mathvariant="sans-serif">μ</mi></semantics></math></inline-formula>m to 3.6 <inline-formula><math display="inline"><semantics><mi mathvariant="sans-serif">μ</mi></semantics></math></inline-formula>m using a tunable mid-infrared optical parametric oscillator. The spectra are attained using wavelength scan rates differing by more than two orders of magnitude (from 0.3 nm s<inline-formula><math display="inline"><semantics><msup><mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></semantics></math></inline-formula> to 96 nm s<inline-formula><math display="inline"><semantics><msup><mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></semantics></math></inline-formula>). With this variation in scan rate, the spectral resolution is found to change from 2.5 cm<inline-formula><math display="inline"><semantics><msup><mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></semantics></math></inline-formula> to 9 cm<inline-formula><math display="inline"><semantics><msup><mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></semantics></math></inline-formula>. The investigated gas samples are methane (in nitrogen) and a gas mixture consisting of methane, water, and ethanol. For the gas mixture, the reduced spectral resolution at fast scan rates significantly complicates the quantification of constituent gas concentrations. |
| first_indexed | 2024-03-10T17:03:29Z |
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| last_indexed | 2024-03-10T17:03:29Z |
| publishDate | 2020-08-01 |
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| spelling | doaj.art-fb9514ec177e4aab984a2f474ad865742023-11-20T10:54:01ZengMDPI AGSensors1424-82202020-08-012017472510.3390/s20174725Intrinsic Spectral Resolution Limitations of QEPAS Sensors for Fast and Broad Wavelength TuningJesper B. Christensen0Lasse Høgstedt1Søren M. M. Friis2Jui-Yu Lai3Ming-Hsien Chou4David Balslev-Harder5Jan C. Petersen6Mikael Lassen7Danish Fundamental Metrology, Kogle Allé 5, 2970 Hørsholm, DenmarkNLIR Aps, Hirsemarken 1, 3520 Farum, DenmarkNLIR Aps, Hirsemarken 1, 3520 Farum, DenmarkHC Photonics, 4F, No. 2, Technology Rd. V, Hsinchu City 300, TaiwanHC Photonics, 4F, No. 2, Technology Rd. V, Hsinchu City 300, TaiwanDanish Fundamental Metrology, Kogle Allé 5, 2970 Hørsholm, DenmarkDanish Fundamental Metrology, Kogle Allé 5, 2970 Hørsholm, DenmarkDanish Fundamental Metrology, Kogle Allé 5, 2970 Hørsholm, DenmarkQuartz-enhanced photoacoustic sensing is a promising method for low-concentration trace-gas monitoring due to the resonant signal enhancement provided by a high-Q quartz tuning fork. However, quartz-enhanced photoacoustic spectroscopy (QEPAS) is associated with a relatively slow acoustic decay, which results in a reduced spectral resolution and signal-to-noise ratio as the wavelength tuning rate is increased. In this work, we investigate the influence of wavelength scan rate on the spectral resolution and signal-to-noise ratio of QEPAS sensors. We demonstrate the acquisition of photoacoustic spectra from 3.1 <inline-formula><math display="inline"><semantics><mi mathvariant="sans-serif">μ</mi></semantics></math></inline-formula>m to 3.6 <inline-formula><math display="inline"><semantics><mi mathvariant="sans-serif">μ</mi></semantics></math></inline-formula>m using a tunable mid-infrared optical parametric oscillator. The spectra are attained using wavelength scan rates differing by more than two orders of magnitude (from 0.3 nm s<inline-formula><math display="inline"><semantics><msup><mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></semantics></math></inline-formula> to 96 nm s<inline-formula><math display="inline"><semantics><msup><mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></semantics></math></inline-formula>). With this variation in scan rate, the spectral resolution is found to change from 2.5 cm<inline-formula><math display="inline"><semantics><msup><mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></semantics></math></inline-formula> to 9 cm<inline-formula><math display="inline"><semantics><msup><mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></semantics></math></inline-formula>. The investigated gas samples are methane (in nitrogen) and a gas mixture consisting of methane, water, and ethanol. For the gas mixture, the reduced spectral resolution at fast scan rates significantly complicates the quantification of constituent gas concentrations.https://www.mdpi.com/1424-8220/20/17/4725quartz-enhanced photoacoustic spectroscopyquartz tuning forkenvironmental sensoroptical parametric oscillatormolecular spectroscopy |
| spellingShingle | Jesper B. Christensen Lasse Høgstedt Søren M. M. Friis Jui-Yu Lai Ming-Hsien Chou David Balslev-Harder Jan C. Petersen Mikael Lassen Intrinsic Spectral Resolution Limitations of QEPAS Sensors for Fast and Broad Wavelength Tuning Sensors quartz-enhanced photoacoustic spectroscopy quartz tuning fork environmental sensor optical parametric oscillator molecular spectroscopy |
| title | Intrinsic Spectral Resolution Limitations of QEPAS Sensors for Fast and Broad Wavelength Tuning |
| title_full | Intrinsic Spectral Resolution Limitations of QEPAS Sensors for Fast and Broad Wavelength Tuning |
| title_fullStr | Intrinsic Spectral Resolution Limitations of QEPAS Sensors for Fast and Broad Wavelength Tuning |
| title_full_unstemmed | Intrinsic Spectral Resolution Limitations of QEPAS Sensors for Fast and Broad Wavelength Tuning |
| title_short | Intrinsic Spectral Resolution Limitations of QEPAS Sensors for Fast and Broad Wavelength Tuning |
| title_sort | intrinsic spectral resolution limitations of qepas sensors for fast and broad wavelength tuning |
| topic | quartz-enhanced photoacoustic spectroscopy quartz tuning fork environmental sensor optical parametric oscillator molecular spectroscopy |
| url | https://www.mdpi.com/1424-8220/20/17/4725 |
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