Measurements of the anomalous dispersion of HF in absorption

Gross, Rolf W. F.; Chodzko, R. A.; Turner, Emma; Coffer, J. G.

doi:10.1109/jqe.1980.1070570

Cited by 10 publications

(4 citation statements)

References 3 publications

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“…Recently similar developments using a tunable diode laser and a heterodyne detection scheme were demonstrated [9]. Other implementations include a laser-based version of the "hook" method in a Mach-Zehnder interferometer configuration for fringe displacement measurements [10,11], the use of a high finesse Fabry Perot resonator [12] or techniques based on intra-resonator measurements [13]. All coherent detection schemes give access to the phase of the electromagnetic wave, from which the dispersion information can be retrieved [14,15].…”

Section: Introductionmentioning

confidence: 99%

Molecular dispersion spectroscopy for chemical sensing using chirped mid-infrared quantum cascade laser

2010

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A spectroscopic method of molecular detection based on dispersion measurements using a frequency-chirped laser source is presented. An infrared quantum cascade laser emitting around 1912 cm(-1) is used as a tunable spectroscopic source to measure dispersion that occurs in the vicinity of molecular ro-vibrational transitions. The sample under study is a mixture of nitric oxide in dry nitrogen. Two experimental configurations based on a coherent detection scheme are investigated and discussed. The theoretical models, which describe the observed spectral signals, are developed and verified experimentally. The method is particularly relevant to optical sensing based on mid-infrared quantum cascade lasers as the high chirp rates available with those sources can significantly enhance the magnitude of the measured dispersion signals. The method relies on heterodyne beatnote frequency measurements and shows high immunity to variations in the optical power received by the photodetector.

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Section: Introductionmentioning

confidence: 99%

Molecular dispersion spectroscopy for chemical sensing using chirped mid-infrared quantum cascade laser

2010

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“…The amount of dispersion (measured as a change in refractive index per unit frequency) is proportional to the concentration of the absorbing species, thus it can be used for quantitative concentration measurements. Attempts to use refractive index measurements for molecular detection had already been made in 1902 [10], but only a few techniques have been implemented to-date for trace gas detection [11–13], and none of them is suitable for remote sensing. In contrast, the ClaDS technique is a promising dispersion-based method that can be used in a remote-sensing configuration and may become an attractive alternative to absorption-based techniques that rely on the Beer-Lambert law.…”

Section: Clads Basic Operation Principlesmentioning

confidence: 99%

Chirped Laser Dispersion Spectroscopy for Remote Open-Path Trace-Gas Sensing

Nikodem

Wysocki

2012

Sensors

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In this paper we present a prototype instrument for remote open-path detection of nitrous oxide. The sensor is based on a 4.53 μm quantum cascade laser and uses the chirped laser dispersion spectroscopy (CLaDS) technique for molecular concentration measurements. To the best of our knowledge this is the first demonstration of open-path laser-based trace-gas detection using a molecular dispersion measurement. The prototype sensor achieves a detection limit down to the single-ppbv level and exhibits excellent stability and robustness. The instrument characterization, field deployment performance, and the advantages of applying dispersion sensing to sensitive trace-gas detection in a remote open-path configuration are presented.

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“…Therefore a new sensing scheme that is capable of measuring molecular dispersion with relatively simple and robust setup has a potential to overcome some of these drawbacks and provide advantages of dispersion spectroscopy. Such attempts have been made in the past, but only a small amount of progress has been made in adoption of proposed techniques to sensitive trace‐gas detection in nonlaboratory conditions 15,19 , 32–37 . Recently we have introduced a new chirped laser dispersion spectroscopy (CLaDS) technique that relies on molecular dispersion sensing in the gas sample, 38 and the system itself can be easily adopted for field measurements 39 .…”

Section: Direct Measurement Of Molecular Refractive Index and Applicamentioning

confidence: 99%

Molecular dispersion spectroscopy – new capabilities in laser chemical sensing

Nikodem

Wysocki

2012

Annals of the New York Academy of Sciences

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Laser spectroscopic techniques suitable for molecular dispersion sensing enable new applications and strategies in chemical detection. This paper discusses the current state-of-the art and provides an overview of recently developed chirped laser dispersion spectroscopy (CLaDS) based techniques. CLaDS and its derivatives allow for quantitative spectroscopy of trace-gases and enable new capabilities such as extended dynamic range of concentration measurements, high immunity to photodetected intensity fluctuations, or capability of direct processing of spectroscopic signals in optical domain. Several experimental configurations based on quantum cascade lasers and examples of molecular spectroscopic data are presented to demonstrate capabilities of molecular dispersion spectroscopy in the mid-infrared spectral region.

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Measurements of the anomalous dispersion of HF in absorption

Cited by 10 publications

References 3 publications

Molecular dispersion spectroscopy for chemical sensing using chirped mid-infrared quantum cascade laser

Molecular dispersion spectroscopy for chemical sensing using chirped mid-infrared quantum cascade laser

Chirped Laser Dispersion Spectroscopy for Remote Open-Path Trace-Gas Sensing

Molecular dispersion spectroscopy – new capabilities in laser chemical sensing

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