Second-harmonic detection with tunable diode lasers ? Comparison of experiment and theory

Reid, J.; Labrie, D.

doi:10.1007/bf00692448

Cited by 595 publications

(242 citation statements)

References 13 publications

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“…The optimal modulation index for 2f detection (m = 2.2 as shown by Reid and Labrie, 1981) cannot be reached with the current QC laser used in our system due to limited current tuning range, which decreases with increasing modulation frequency (Tao et al, 2012a). We can only achieve a modulation index of ∼ 1.4 for NH 3 measurements.…”

Section: Field Measurementsmentioning

confidence: 92%

“…As shown in Fig. 2b, second harmonic (2f) detection minimizes the water vapor absorption baseline and improves sensitivity and selectivity (Reid and Labrie, 1981). Other atmospheric species such as CO 2 , O 3 and SO 2 also absorb in this region below ∼ 5×10 −5 fractional absorption.…”

Section: Spectroscopymentioning

confidence: 98%

“…Although higher ramp and modulation frequencies should improve sensitivity by minimizing laser excess noise, the decrease in tuning rate at higher frequencies, the broad spectral features probed, and practical QC laser tuning rate limitations prevent us from going to higher frequencies. The tuning rate limitations allow us to achieve a modulation index of ∼ 1.4 for NH 3 measurements, which is not at the most sensitive, optimal value of 2.2 (Reid and Labrie, 1981).…”

Section: Sensor Setupmentioning

confidence: 99%

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Open-path, quantum cascade-laser-based sensor for high-resolution atmospheric ammonia measurements

et al. 2014

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Abstract. We demonstrate a compact, open-path, quantum cascade-laser-based atmospheric ammonia sensor operating at 9.06 µm for high-sensitivity, high temporal resolution, ground-based measurements. Atmospheric ammonia (NH 3 ) is a gas-phase precursor to fine particulate matter, with implications for air quality and climate change. Currently, NH 3 sensing challenges have led to a lack of widespread in situ measurements. Our open-path sensor configuration minimizes sampling artifacts associated with NH 3 surface adsorption onto inlet tubing and reduced pressure sampling cells, as well as condensed-phase partitioning ambiguities. Multi-harmonic wavelength modulation spectroscopy allows for selective and sensitive detection of atmospheric pressurebroadened absorption features. An in-line ethylene reference cell provides real-time calibration (±20 % accuracy) and normalization for instrument drift under rapidly changing field conditions. The sensor has a sensitivity and noise-equivalent limit (1σ ) of 0.15 ppbv NH 3 at 10 Hz, a mass of ∼ 5 kg and consumes ∼ 50 W of electrical power. The total uncertainty in NH 3 measurements is 0.20 ppbv NH 3 ± 10 %, based on a spectroscopic calibration method. Field performance of this open-path NH 3 sensor is demonstrated, with 10 Hz time resolution and a large dynamic response for in situ NH 3 measurements. This sensor provides the capabilities for improved in situ gas-phase NH 3 sensing relevant for emission source characterization and flux measurements.

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Section: Field Measurementsmentioning

confidence: 92%

Section: Spectroscopymentioning

confidence: 98%

Section: Sensor Setupmentioning

confidence: 99%

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Open-path, quantum cascade-laser-based sensor for high-resolution atmospheric ammonia measurements

et al. 2014

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“…At 1 second of averaging, the corresponding numbers are 5 × 10 −7 and 9 × 10 −7 , respectively. The decrease in sensitivity at higher harmonics is to be expected due to the lower signal values [23,24]. Although the 1f -WMS signal provides the strongest WMS signal, it is often not selected due to the unwanted RAM offset and the higher sensitivity to optical noise.…”

Section: System Performancementioning

confidence: 99%

Fast and sensitive time-multiplexed gas sensing of multiple lines using a miniature telecom diode laser between 1529 nm and 1565 nm

et al. 2011

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High-sensitive multi-species detection around 1550 nm using a modulated grating Y-branch, MG-Y, diode laser tunable between 1529 nm and 1565 nm is presented. The MG-Y diode laser is based on the Vernier effect of two modulated gratings, and exhibits quasi-continuous tuning over 36 nm. Multi-species detection is achieved by fast sequential scanning of single absorption lines of CH 4 , CO, C 2 H 2 , and CO 2 distributed over the tuning range of the diode laser. The laser wavelength is scanned about 10 GHz around each absorption line for 5 ms and this is followed by a discrete large jump in operating wavelength to the next line.The MG-Y diode laser has a good repeatability in output frequency between sequential scan segments (<10 MHz) enabling averaging of the scans. The setup employs digital wavelength modulation spectroscopy, dWMS, with Fourier-

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“…In this way, different molecules can be identified while avoiding interference from other spectra. According to this technique, the near-infrared waveband is matched with the low-loss window of an optical fiber, and by using such optical fibers, the remote transport of a light beam is realized [3][4][5][6]. Moreover, the remote, on-line, and real-time detection of the gas concentration is achieved by combining TDLAS and optical fiber sensing techniques.…”

Section: Introductionmentioning

confidence: 99%

A coal mine multi-point fiber ethylene gas concentration sensor

et al. 2015

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Spontaneous combustion of the coal mine goaf is one of the main disasters in the coal mine. The detection technology based on symbolic gas is the main means to realize the spontaneous combustion prediction of the coal mine goaf, and ethylene gas is an important symbol gas of spontaneous combustion in the coal accelerated oxidation stage. In order to overcome the problem of current coal ethylene detection, the paper presents a mine optical fiber multi-point ethylene concentration sensor based on the tunable diode laser absorption spectroscopy. Based on the experiments and analysis of the near-infrared spectrum of ethylene, the system employed the 1.62 μm (DFB) wavelength fiber coupled distributed feedback laser as the light source. By using the wavelength scanning technique and developing a stable fiber coupled Herriot type long path gas absorption cell, a ppm-level high sensitivity detecting system for the concentration of ethylene gas was realized, which could meet the needs of coal mine fire prevention goaf prediction.

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Second-harmonic detection with tunable diode lasers ? Comparison of experiment and theory

Cited by 595 publications

References 13 publications

Open-path, quantum cascade-laser-based sensor for high-resolution atmospheric ammonia measurements

Open-path, quantum cascade-laser-based sensor for high-resolution atmospheric ammonia measurements

Fast and sensitive time-multiplexed gas sensing of multiple lines using a miniature telecom diode laser between 1529 nm and 1565 nm

A coal mine multi-point fiber ethylene gas concentration sensor

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