A Rapidly Tunable Laser System for Measurements of NH<sub>2</sub> at 597 nm Behind Reflected Shock Waves
Distributed feedback lasers, which feature rapid wavelength tunability, are not presently available in the yellow and orange spectral regions, impeding spectroscopic studies of short-lived species that absorb light in this range. To meet this need, a rapidly tunable laser system was constructed, cha...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2024-12-01
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| Series: | Sensors |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1424-8220/24/24/7920 |
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| Summary: | Distributed feedback lasers, which feature rapid wavelength tunability, are not presently available in the yellow and orange spectral regions, impeding spectroscopic studies of short-lived species that absorb light in this range. To meet this need, a rapidly tunable laser system was constructed, characterized, and demonstrated for measurements of the NH<sub>2</sub> radical at 597.4 nm. The system consisted of three main parts: (1) a distributed feedback diode laser operating at 1194.8 nm, (2) a fiber-coupled optical amplifier, and (3) a periodically poled lithium niobate (PPLN) waveguide for second-harmonic generation. A phase-matching optical frequency bandwidth of 118 GHz and a second-harmonic generation efficiency of 109%/W were determined for the PPLN waveguide, and the intensity and wavelength stability of the system were measured. The rapid-tuning capabilities of the laser system were characterized to explore its potential for use in scanned-direct absorption and wavelength modulation spectroscopy experiments. The feasibility of scanned-direct absorption up to a scan rate of 900 kHz and wavelength modulation spectroscopy at modulation frequencies up to 800 kHz were demonstrated. Finally, the system was deployed in a series of shock tube experiments in which the concentration of NH<sub>2</sub> radicals was measured during the decomposition of NH<sub>3</sub> behind reflected shock waves. |
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| ISSN: | 1424-8220 |