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State-of-the-art nonlinear optical technologies for frequency comb generation provide new powerful instruments for molecular physics and spectroscopy. Selected illustrations are given.
Attenuated total reflection spectroscopy with tapered fibers is combined to coherent multi-heterodyne spectroscopy in the near-infrared region. Evanescent sensing is extended to broadband high-resolution spectroscopy in the gas phase at high signal-to-noise ratio.
Laser frequency comb generators produce an optical spectrum, which consists of several hundred thousands of perfectly evenly spaced spectral lines. Such combs have revolutionized the field of time and frequency metrology. They are now becoming enabling tools for an increasing number of applications in science and technology, most of which much beyond the original purpose of accurate frequency measurements.
Real-time absorption and dispersion dual-comb spectroscopy is achieved in the 3-μm region without mode-locked lasers or active stabilization. The resolved lines of flat-top frequency combs with adjustable line-spacing and tunable center wavelength enable precise spectroscopy.
Multiheterodyne frequency comb spectroscopy without mode-locked lasers is reported in the near-infrared C and L telecommunication bands. The system without active stabilization combines high signal-to-noise ratio, rapid tuning and moderate multiplex spectral span.
Coherent anti-Stokes Raman spectroscopy is achieved on microsecond time scale with two frequency combs and a heterodyne detection with a local oscillator. The vibrational transitions reach a signal-to-noise ratio of 1600 with linear concentration dependence.
With the help of the strong nonlinear optical response in silicon nanophotonic wire waveguides complex sources and devices can be integrated on a chip. We demonstrate mid-infrared wavelength translators and frequency combs Furthermore, we open up the possibility for the integration of nonlinear optical functions at telecom wavelengths by exploiting more exotic nonlinear interactions in silicon waveguides...
A mid-infrared octave spanning frequency comb is generated in a silicon waveguide. By beating the generated comb on a photodetector with a narrow linewidth lightsource the linewidth of the lines is measured to be <100kHz.
We characterize a new mid-infrared frequency comb generator based on difference frequency generation around 3.1 μm. High power per comb mode (>10−7 W/mode) is obtained over a broad spectral span (>750 nm, >790 cm−1). The source is used for direct absorption spectroscopy with a Michelson-based Fourier transform interferometer.
Ultra-rapid coherent Stokes and anti-Stokes Raman spectroscopy with two laser frequency combs is demonstrated. Spectra and hyperspectral images are measured over a span of 1200 cm−1 at 4 cm−1 resolution within 15 microseconds.
A new concept of real-time dual-comb spectroscopy that only uses free-running femtosecond mode-locked lasers provides high quality Fourier spectra with resolved comb lines over 12 THz spectral span without a posteriori data processing.
Nonlinear coherent Raman scattering with ultra-short pulse lasers has opened up new opportunities for nonintrusive three-dimensional label-free chemical sensing [1]. A single ultrashort pulse laser, combined to a pulse shaper or a Michelson interferometer (for a review, see [2]), allows for multiplex measurements. However, measuring a broad spectral bandwidth spectrum at high resolution within a very...
We present the latest results in extending dual-comb spectroscopy to two-photon resonances. By measuring two-photon excitation of rubidium vapor and water-dissolved fluorophores, we demonstrate both the high resolution and speed of the technique.
Ultra-rapid coherent anti-Stokes Raman spectroscopy with two laser frequency combs is demonstrated. Hyperspectral images are acquired over a spectral bandwidth of 1200 cm−1 with a resolution of 10 cm−1 at a rate of 50 pixels/s.
We present a new technique of non-linear dual-comb spectroscopy for the measurement of coherent Stokes and anti-Stokes Raman spectra of fundamental vibrational transitions. Ultrarapid acquisition times, high-resolution, broad-spectral-span are the main characteristics of our experiments.
Dual-comb spectroscopy is extended to the visible range. The dense rovibronic spectrum of iodine around 520 nm is measured within 12 ms at Doppler-limited resolution with a scheme that only uses free-running lasers.
Nonlinear dual-frequency-comb spectroscopy is demonstrated with multi-heterodyne femtosecond Raman-induced Kerr-effect spectroscopy. Spectra of liquid samples are recorded with a spectral resolution of 200 GHz, a measurement time of 350 μs and a sensitivity of 10−6.
A new scheme of real-time dual-comb spectroscopy that only uses free-running femtosecond lasers provides distortion-free Fourier spectra with resolved comb lines across the full spectral span of erbium-doped fiber lasers (>80 nm centered around 1550 nm) without a posteriori data processing.
Recent experiments of multi-heterodyne dual-comb spectroscopy have demonstrated that the precisely spaced spectral lines of laser frequency combs can be harnessed for the rapid and sensitive acquisition of highly multiplexed spectra of molecules. The very exciting potential of dual-comb spectroscopy [1] without moving parts mostly lies in recording times that could be shortened from seconds to microseconds...
The millions of precisely controlled laser comb lines produced with a train of ultrashort laser pulses can harnessed for highly-multiplexed molecular spectroscopy. Multi-heterodyne spectroscopy with frequency combs is emerging as a powerful new tool.
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