Surpassing the path-limited resolution of Fourier-transform spectrometry with frequency combs

Masłowski, Piotr; Lee, Kevin F.; Johansson, Alexandra C.; Khodabakhsh, Amir; Kowzan, Grzegorz; Rutkowski, Lucile; Mills, Andrew A.; Mohr, Christian; Jiang, Jie; Fermann, M. E.; Foltynowicz, Aleksandra

doi:10.1103/physreva.93.021802

Cited by 148 publications

(100 citation statements)

References 38 publications

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“…Fourier transform spectroscopy (FTS) can be implemented either with a mechanical interferometer [3,[7][8][9][10][11] or using the dual-comb technique [4,12,13]. Both approaches enable measurements with frequency resolution and precision provided by the comb with no influence of the instrumental line shape and are suitable for broadband precision spectroscopy [4,14]. Mechanical MIR FTS has been successfully combined with enhancement cavities [6,15] and enabled, e.g., acquisition of rotationally resolved spectra of cold complex molecules [16].…”

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confidence: 99%

Mid-infrared continuous-filtering Vernier spectroscopy using a doubly resonant optical parametric oscillator

et al. 2017

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We present a continuous-filtering Vernier spectrometer operating in the 3.15-3.4 µm range, based on a femtosecond doubly resonant optical parametric oscillator, a cavity with a finesse of 340, a grating mounted on a galvo scanner and two photodiodes. The spectrometer allows acquisition of one spectrum spanning 250 nm of bandwidth in 25 ms with 8 GHz resolution, sufficient for resolving molecular lines at atmospheric pressure. An active lock ensures good frequency and intensity stability of the consecutive spectra and enables continuous signal acquisition and efficient averaging. The relative frequency scale is calibrated using a Fabry-Perot etalon or, alternatively, the galvo scanner position signal. We measure spectra of pure CH 4 as well as dry and laboratory air and extract CH 4 and H 2 O concentrations by multiline fitting of model spectra. The figure of merit of the spectrometer is 1.7×10 −9 cm −1 Hz −1/2 per spectral element and the minimum detectable concentration of CH 4 is 360 ppt Hz -1/2 , averaging down to 90 ppt after 16 s.

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Section: Introductionmentioning

confidence: 99%

Mid-infrared continuous-filtering Vernier spectroscopy using a doubly resonant optical parametric oscillator

et al. 2017

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“…Recent advances in comb-based Fourier transform spectroscopy have provided means to measure spectra over the entire comb bandwidth with resolution directly given by the comb linewidth, using either dual-comb spectrometers [14][15][16][17] or mechanical Fourier transform spectrometers (FTS) [18]. Here we use a frequency comb and a mechanical FTS with sub-nominal resolution [18] to directly measure broadband transmission spectra of a high finesse cavity with high signal-to-noise ratio and frequency precision and accuracy.…”

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confidence: 99%

“…Here we use a frequency comb and a mechanical FTS with sub-nominal resolution [18] to directly measure broadband transmission spectra of a high finesse cavity with high signal-to-noise ratio and frequency precision and accuracy. We fully characterize the cavity modes in terms of amplitude, width, and center frequency.…”

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“…The transmitted light, containing both the comb and the cw laser frequencies, was analyzed with a fast-scanning mechanical FTS equipped with an auto-balancing detector [8,22]. The nominal resolution of the FTS was set to T rep f /3 = 333 MHz, which allowed precise sampling of the intensities of the individual comb lines and the cw laser without distortion induced by the instrumental line shape of the FTS [18]. For a given frep value, the spectrum contained 1 spectral element per transmitted comb line, separated by 2 sampling points with intensities at the noise level (except for the point sampling the cw laser frequency).…”

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Sensitive and broadband measurement of dispersion in a cavity using a Fourier transform spectrometer with kHz resolution

Rutkowski¹,

Johansson²,

Gang³

et al. 2017

Opt. Express

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Optical cavities provide high sensitivity to dispersion since their resonance frequencies depend on the index of refraction. We present a direct, broadband, and accurate measurement of the modes of a high finesse cavity using an optical frequency comb and a mechanical Fourier transform spectrometer with a kHz-level resolution. We characterize 16000 cavity modes spanning 16 THz of bandwidth in terms of center frequency, linewidth, and amplitude. We retrieve the group delay dispersion of the cavity mirror coatings and pure N2 with 0.1 fs 2 precision and 1 fs 2 accuracy, as well as the refractivity of the 3ν1+ν3 absorption band of CO2 with 5 × 10 -12 precision. This opens up for broadband refractive index metrology and calibration-free spectroscopy of entire molecular bands.OCIS codes : (140.4780) Optical resonators; (300.6300) Spectroscopy, Fourier transform; (260.2030) Physical optics, dispersion.Fabry-Perot cavities in combination with narrow linewidth continuous wave (cw) lasers are versatile tools for ultra-sensitive measurements of displacement, absorption, and dispersion. For example, high precision measurements of minute length variation of Fabry-Perot cavities enable detection of gravitational waves [1]. A pressure sensor based on the measurement of gas refractivity inside a cavity can outperform a manometer [2]. Cavity-enhanced molecular absorption [3,4] and dispersion [5,6] spectroscopies, which rely on the measurement of intracavity absorption losses and dispersion induced shifts of the cavity modes, respectively, provide complementary information about the molecular transitions and high sensitivity to absorption/dispersion. However, cw lasers allow such measurements only over narrow bandwidths, typically in the sub-THz range. Optical frequency combs, whose spectra consist of thousands of equidistant narrow lines, can probe cavity modes over a much broader bandwidth. In cavity-enhanced optical frequency comb absorption spectroscopy, spectra of entire molecular bands can be acquired with high resolution in short acquisition times [7][8][9][10]. Combs are also an ideal tool for measurements of broadband cavity dispersion induced either by the cavity mirror coatings or intracavity samples. However, previous demonstrations [11-13] did not fully benefit from the high frequency accuracy provided by the comb and suffered from poor spectral resolution (at the THz level).Recent advances in comb-based Fourier transform spectroscopy have provided means to measure spectra over the entire comb bandwidth with resolution directly given by the comb linewidth, using either dual-comb spectrometers [14][15][16][17] or mechanical Fourier transform spectrometers (FTS) [18]. Here we use a frequency comb and a mechanical FTS with sub-nominal resolution [18] to directly measure broadband transmission spectra of a high finesse cavity with high signal-to-noise ratio and frequency precision and accuracy. We fully characterize the cavity modes in terms of amplitude, width, and center frequency. From the shift of the cavity mod...

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“…Moreover, the spectra are free from any influence of the instrumental lineshape function [21]. The multipass cell (Aerodyne Research, AMAC-76LW) is ~32 cm long and configured for 238 passes, which results in 76 m optical path length, and it is connected to a gas flow system and a vacuum pump.…”

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Fourier transform and Vernier spectroscopy using an optical frequency comb at 3–54 μm

et al. 2016

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We present a versatile mid-infrared frequency comb spectroscopy system based on a doubly resonant optical parametric oscillator tunable in the 3-5.4 μm range and two detection methods, a Fourier transform spectrometer (FTS) and a Vernier spectrometer. Using the FTS with a multipass cell we measure high-precision broadband absorption spectra of CH4 and NO at ~3.3 μm and ~5.2 μm, respectively, and of atmospheric species (CH4, CO, CO2 and H2O) in air in the signal and idler wavelength range. The figure of merit of the system is on the order of 10 −8 cm −1 Hz −1∕2 per spectral element, and multiline fitting yields minimum detectable concentrations of 10-20 ppb Hz −1∕2 for CH4, NO and CO. For the first time in the mid-infrared, we perform continuous-filtering Vernier spectroscopy using a low finesse enhancement cavity, a grating and a single detector, and measure the absorption spectrum of CH4 and H2O in ambient air at ~3.3 μm. © 2016 Optical Society of America OCIS codes : (190.4410) Nonlinear optics, (190.7110) Ultrafast nonlinear optics; (190.4970 Optical frequency comb sources in the mid-infrared (MIR) wavelength range (3-12 µm) have large potential for molecular spectroscopy, since the fundamental absorption bands of many species lie in this fingerprint region [1,2]. The maximum achievable wavelength of low repetition rate (<1 GHz) direct comb sources is still limited to <3 µm, and longer wavelengths (>3 µm) can only be reached through nonlinear frequency conversion. Sources based on difference frequency generation (DFG) offer wide wavelength coverage in the MIR, but suffer from poor conversion efficiency [3,4]. Higher average output power is provided by synchronously-pumped optical parametric oscillators (OPOs) [5,6]. In particular, OPOs based on orientation-patterned gallium arsenide (OP-GaAs) crystals pumped by Cr:ZnSe or Tm:fiber femtosecond lasers have made it possible to reach wavelengths beyond ~4.8 µm, a barrier for the well-established oxidebased materials [7,8]. Both DFG and OPO sources have been used for MIR optical frequency comb spectroscopy with different detection methods, namely a Fourier transform spectrometer [9-13], a virtually imaged phased array (VIPA) [14,15], mode-resolved Vernier spectroscopy [16], and dual comb spectroscopy [17,18]. However, the spectral range of all previous demonstrations was limited to <4.8 µm.Here we report a versatile optical frequency comb spectroscopy system based on a doubly resonant optical parametric oscillator (DROPO) with an OP-GaAs crystal operating in the 3-5.4 µm wavelength range. The system incorporates two detection methods, a fast-scanning Fourier transform spectrometer (FTS) in combination with a multipass cell, and a continuous-filtering Vernier spectrometer. The FTS provides ultra-broadband spectral coverage, absolute frequency calibration and high precision in the absorption measurement. We demonstrate this by acquiring absorption spectra of CH4, NO, and ambient air in the signal and idler ranges and comparing the results to the theoretical mod...

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Surpassing the path-limited resolution of Fourier-transform spectrometry with frequency combs

Cited by 148 publications

References 38 publications

Mid-infrared continuous-filtering Vernier spectroscopy using a doubly resonant optical parametric oscillator

Mid-infrared continuous-filtering Vernier spectroscopy using a doubly resonant optical parametric oscillator

Sensitive and broadband measurement of dispersion in a cavity using a Fourier transform spectrometer with kHz resolution

Fourier transform and Vernier spectroscopy using an optical frequency comb at 3–54 μm

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