Cavity-locked ring-down spectroscopy

Paldus, Barbara A.; Harb, C. C.; Spence, Thomas G.; Wilke, B.; Xie, Jianping; Harris, James S.; Zare, Richard N.

doi:10.1063/1.367155

Cited by 147 publications

(86 citation statements)

References 20 publications

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“…To achieve their full potential, such experiments must actively lock the probe laser frequency to the cavity and match the source spectral shape and spatial profile to the cavity frequency and spatial modes -a difficult task that requires complex and expensive equipment [8,9].…”

Section: Principles Of Cavity-enhanced Methodsmentioning

confidence: 99%

Time-resolved broadband cavity-enhanced absorption spectroscopy for chemical kinetics.

Sheps¹,

Chandler²

2013

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Experimental measurements of elementary reaction rate coefficients and product branching ratios are essential to our understanding of many fundamentally important processes in Combustion Chemistry. However, such measurements are often impossible because of a lack of adequate detection techniques. Some of the largest gaps in our knowledge concern some of the most important radical species, because their short lifetimes and low steady-state concentrations make them particularly difficult to detect. To address this challenge, we propose a novel general detection method for gas-phase chemical kinetics: time-resolved broadband cavity-enhanced absorption spectroscopy (TR-BB-CEAS). This all-optical, non-intrusive, multiplexed method enables sensitive direct probing of transient reaction intermediates in a simple, inexpensive, and robust experimental package. 4 ACKNOWLEDGMENTSWe thank Dr. David Osborn (8353) and Dr. Steven S. Brown (NOAA, Boulder, CO) for helpful discussions regarding cavity-enhanced optical methods and experimental design. We also thank Dr. Craig Taatjes (8353) for the use of lab space and for the loan of a YAG laser and optics. 5

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Section: Principles Of Cavity-enhanced Methodsmentioning

confidence: 99%

Time-resolved broadband cavity-enhanced absorption spectroscopy for chemical kinetics.

Sheps¹,

Chandler²

2013

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“…One of the advances that has contributed to higher precision in CRDS instruments is the use of feedback to stabilize the laser frequency on a mode of the cavity 23,[39][40][41] . This enables the build-up of energy in the cavity to occur more efficiently (and therefore more rapidly), allows for faster acquisition of ringdowns, and reduces error in determining the laser frequency by using the equally spaced cavity mode frequencies as a scale.…”

Section: Chapter 3 Cavity-laser Lockingmentioning

confidence: 99%

“…In 1998, Paldus et.al. 40 , used optical feedback (see Since their design swept through each mode successively, their system's sensitivity was limited by the number of samples at each mode they could capture before mechanical instabilities offset any improvement by added decay constant averaging. Their system achieved a sensitivity of 5 x 10 -10 cm -1 .…”

Section: Current State Of the Science For High-precision/high-speed Crdsmentioning

confidence: 99%

Modifications to a Cavity Ringdown Spectrometer to Improve Data Acquisition Rates

Bostrom¹

2000

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Cavity ringdown spectroscopy (CRDS) makes use of light retention in an optical cavity to enhance the sensitivity to absorption or extinction of light from a sample inside the cavity. When light entering the cavity is stopped, the output is an exponential decay with a decay constant that can be used to determine the quantity of the analyte if the extinction or absorption coefficient is known. The precision of the CRDS is dependent on the rate at which the system it acquires and processes ringdowns, assuming randomly distributed errors. We have demonstrated a CRDS system with a ringdown acquisition rate of 1.5 kHz, extendable to a maximum of 3.5 kHz, using new techniques that significantly changed the way in which the ringdowns are both initiated and processed.On the initiation side, we combined a custom high-resolution laser controller with a linear optical feedback configuration and a novel optical technique for initiating a ringdown.Our optical injection "unlock" method switches the laser off-resonance, while allowing the laser to immediately return to resonance, after terminating the unlock, to allow for another ringdown (on the same cavity resonance mode). This part of the system had a demonstrated ringdown initiation rate of 3.5 kHz. To take advantage of this rate, we developed an optimized cost-effective FGPA-based data acquisition and processing system for CRDS, capable of determining decay constants at a maximum rate of 4.4 kHz, by modifying a commercial ADC-FPGA evaluation board and programming it to apply a discrete Fourier transform-based algorithm for determining decay constants. The entire system shows promise with a demonstrated ability to determine gas concentrations for H 2 O with a measured concentration accuracy of ±3.3%. The system achieved an ii absorption coefficient precision of 0.1% (95% confidence interval). It also exhibited a linear response for varying H 2 O concentrations, a 2.2% variation (1σ) for repeated measurements at the same H 2 O concentration, and a corresponding precision of 0.6% (standard error of the mean). The absorption coefficient limit of detection was determined to be 1.6 x 10 -8 cm -1 (root mean square of the baseline residual). Proposed modifications to our prototype system offer the promise of more substantial gains in both precision and limit of detection. The system components developed here for faster ringdown acquisition and processing have broader applications for CRDS in atmospheric science and other fields that need fast response systems operating at high-precision.iii DedicationTo my wife, Alison, without whose continual support and encouragement I could never have come close to accomplishing this.To my daughter, Naomi, who has only ever known me to be a graduate student-may she always appreciate physics the way she does now.To my Dad, whom I think would have really liked to have seen this, and to myMom, who has been proud enough of me for both of them.iv

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“…1 During the last decade there have been widespread CRD applications, and a number of novel variations have emerged for advanced implementations. [2][3][4][5][6][7][8][9][10][11] Among them is the realization of the CRD technique in ''spatial'' domain rather than in ''time'' domain, 12 which features a new optical arrangement using a plane Fabry-Perot ͑PFP͒ cavity in combination with a narrow, collimated cw laser beam in oblique incidence as Fig. 1 illustrates.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, the SCRD technique can be realized without the need for fast and sophisticated control mechanisms such as a cavity-lock servo, a cavity dither circuitry, a fast laser turn-off driver, and a rapid cavity excursion procedure that are indispensable for the conventional CRD technique using cw lasers. [8][9][10] Data acquisition is made more efficient through time-averaged cw detection, even with the use of low-grade slow detection systems since the SCRD technique does not rely on the repetition rate and the duration of transient CRD events. Such less-demanding technical configuration for producing and detecting CRD signals should allow an extension of spectral coverage of the CRD technique.…”

Section: Introductionmentioning

confidence: 99%

Spatial-domain cavity ringdown from a high-finesse plane Fabry–Perot cavity

Lee

Kim

Yoo

et al. 2002

Journal of Applied Physics

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We investigate the optical transmission of a tilted plane Fabry-Perot cavity leading to spatial cavity ringdown, the exponentially decaying intensity output present along the transverse spatial coordinate. Primary features of the spatial cavity ringdown are theoretically predicted from the spectral and spatial cavity transfer function which is derived analytically on the combined basis of ray optics and diffraction theory applied to an ideal diffraction lossless cavity of one transverse dimension. Spatial frequency filtration by a narrow Lorentzian-shaped cavity resonance is shown to play key roles on the spatial aspects of transmitted beam profiles. Our theoretical formulation is further extended to the case of wedged plane Fabry-Perot cavities. The experimental observation of spatial cavity ringdown signals exhibits an excellent agreement with the theoretical prediction.

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Cavity-locked ring-down spectroscopy

Cited by 147 publications

References 20 publications

Time-resolved broadband cavity-enhanced absorption spectroscopy for chemical kinetics.

Time-resolved broadband cavity-enhanced absorption spectroscopy for chemical kinetics.

Modifications to a Cavity Ringdown Spectrometer to Improve Data Acquisition Rates

Spatial-domain cavity ringdown from a high-finesse plane Fabry–Perot cavity

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