Broadband molecular spectroscopy with optical frequency combs

Weichman, Marissa L.; Changala, P. Bryan; Chen, Zaijun; Yan, Ming; Picqué, N.

doi:10.1016/j.jms.2018.11.011

Cited by 63 publications

(49 citation statements)

References 148 publications

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“…In many ways, frequency generation with short-pulsed laser systems enables the only means for broad spectroscopic coverage at some wavelengths with high brightness. This is particularly true in the mid-IR to the terahertz 49,50 and the ultraviolet (UV) to the XUV 51,52 . The more extreme demonstration of bandwidth extension has been to wavelengths as long as 27 μm 53 using a combination of difference frequency generation (DFG) and/or optical parametric oscillation (OPO) 49,[54][55][56][57] .…”

Section: What Is An Ofc and How Does It Workmentioning

confidence: 99%

“…As a result, spectroscopic measurement with OFCs has been explored over vast portions of the electro-magnetic spectrum, extending from the terahertz to the UV. A concerted effort has also been devoted toward coverage in the mid-IR region, to access stronger molecular cross-sections 49,53,56,57,84 , and OFC-based spectroscopy has also been reported on extensively in various review articles (see for example 50,[138][139][140] ). More specifically, direct spectroscopy with OFCs has been applied to study ultra-cold molecules 141 , human breath analysis 142 , time-resolved spectroscopy 143,144 , and highprecision molecular spectroscopy 145,146 .…”

Section: Ofc Applicationsmentioning

confidence: 99%

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20 years of developments in optical frequency comb technology and applications

2019

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Optical frequency combs were developed nearly two decades ago to support the world's most precise atomic clocks. Acting as precision optical synthesizers, frequency combs enable the precise transfer of phase and frequency information from a high-stability reference to hundreds of thousands of tones in the optical domain. This versatility, coupled with nearcontinuous spectroscopic coverage from microwave frequencies to the extreme ultraviolet , has enabled precision measurement capabilities in both fundamental and applied contexts. This review takes a tutorial approach to illustrate how 20 years of source development and technology has facilitated the journey of optical frequency combs from the lab into the field. T he optical frequency comb (OFC) was originally developed to count the cycles from optical atomic clocks. Atoms make ideal frequency references because they are identical, and hence reproducible, with discrete and well-defined energy levels that are dominated by strong internal forces that naturally isolate them from external perturbations. Consequently, in 1967 the international standard unit of time, the SI second was redefined as 9,192,631,770 oscillations between two hyper-fine states in 133 Cs 1. While 133 Cs microwave clocks provide an astounding 16 digits in frequency/time accuracy, clocks based on optical transitions in atoms are being explored as alternative references because higher transition frequencies permit greater than a 100 times improvement in time/frequency resolution (see "Timing, synchronization, and atomic clock networks"). Optical signals, however, pose a significant measurement challenge because light frequencies oscillate 100,000 times faster than state-of-the-art digital electronics. Prior to 2000, the simplest method to access an optical frequency was via knowledge of the speed of light and measurement of its wavelength, accessible with relatively poor precision of parts in 10 7 using an optical wavemeter. For precision measurements seeking resolutions better than that offered by wavelength standards, large-scale frequency chains were used to connect the microwave definition of the Hertz, provided by the 133 Cs primary frequency reference near 9.2 GHz, to the optical domain via a series of multiplied and phase-locked oscillators 2. The most complicated of these systems required up to 10 scientists, 20 different oscillators and 50 feedback loops to perform a single optical measurement 3. Because of the complexity, frequency multiplication chains yielded one to two precision optical frequency measurements per year. In 2000, the realization of the OFC allowed for the replacement of these complex frequency chains with a

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Section: What Is An Ofc and How Does It Workmentioning

confidence: 99%

Section: Ofc Applicationsmentioning

confidence: 99%

20 years of developments in optical frequency comb technology and applications

2019

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“…198 There are now myriad examples of CE-DFCS for molecular spectroscopy with a variety of comb sources and schemes for broadband, simultaneous detection, and the interested reader is directed one of many excellent reviews in this area. 194,195,199,200,201 Figure 5c shows data from a near-IR frequency comb multipass optical absorption experiment on the analysis of acetylene, illustrating the broad spectral coverage, sensitivity and specificity achievable. 203 Despite the clear advantages of OFCs for plasma analysis, a field which could take advantage of the rapid, massively parallel acquisition afforded by OFC spectroscopy, there is to our knowledge only one previously reported study in this area, which is that by Golkowski et al 204 who used a mid-IR comb in combination with a multi-pass cell (36 m pathlength) to probe the effluent of a non-thermal medical plasma.…”

Section: Determination Of Radical Densities In the Gas Phasementioning

confidence: 99%

Spectroscopy techniques and the measurement of molecular radical densities in atmospheric pressure plasmas

Peverall

Ritchie

2019

Plasma Sources Sci. Technol.

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Cold atmospheric pressure plasmas (CAPs) are finding an increasing number of applications in diverse fields such as sterilization, medicine and dentistry, because they induce chemical reactivity at nearambient temperature. These plasmas are usually generated in noble gas flows which propagate into air, resulting in the production of a wide variety of species which can cause primary and secondary chemistry in both the gas and liquid phases. Detailed understanding of this low temperature reactivity requires selective and sensitive measurements of radical species. In this review we focus upon several techniques from a methodological point of view that are suitable for the sensitive detection of reactive species, or show promise for this purpose. A range of traditional and contemporary spectroscopic methods for measuring across different phases is highlighted in an attempt to present a 'detection landscape' for CAP-borne radicals.

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“…In the past decade, mid-infrared Dual-Comb Spectroscopy (DCS) [22][23][24] has emerged as an alternative technique to traditional FTS, providing sub-second sampling times. In DCS, the interferogram is made by the interference of femtosecond pulses from two mode-locked lasers, each generating a frequency comb, which have a slightly different repetition frequency with respect to each other.…”

Section: Introductionmentioning

confidence: 99%

Broadband Time-Resolved Absorption and Dispersion Spectroscopy of Methane and Ethane in A Plasma Using a Mid-Infrared Dual-Comb Spectrometer

Abbas¹,

Dijk²,

Jahromi³

et al. 2020

Preprint

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Conventional mechanical Fourier Transform Spectrometers (FTS) are able to simultaneously measure absorption and dispersion spectra of gas-phase samples. However, they usually need very long measurement times to achieve time-resolved spectra with a good spectral and temporal resolution. Here, we present a mid-infrared dual-comb-based FTS in an asymmetric configuration, providing broadband absorption and dispersion spectra with a spectral resolution of 5 GHz, a temporal resolution of 20 μs, and a total measurement time of a few minutes. We used the dual-comb spectrometer to monitor the reaction dynamics of methane and ethane in an electrical plasma discharge. We observed ethane/methane formation as a recombination reaction of hydrocarbon radicals in the discharge in various static and dynamic conditions. The results demonstrate a new analytical approach for measuring fast molecular absorption and dispersion changes and monitoring fast dynamics of chemical reactions, which can be interesting for chemical kinetic research and particularly for the combustion and plasma analysis community.

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Broadband molecular spectroscopy with optical frequency combs

Cited by 63 publications

References 148 publications

20 years of developments in optical frequency comb technology and applications

20 years of developments in optical frequency comb technology and applications

Spectroscopy techniques and the measurement of molecular radical densities in atmospheric pressure plasmas

Broadband Time-Resolved Absorption and Dispersion Spectroscopy of Methane and Ethane in A Plasma Using a Mid-Infrared Dual-Comb Spectrometer

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