24 research outputs found
Dual Comb Spectroscopy
List of publications Conference contribution
Coherent Raman spectro-imaging with laser frequency combs
Optical spectroscopy and imaging of microscopic samples have opened up a wide
range of applications throughout the physical, chemical, and biological
sciences. High chemical specificity may be achieved by directly interrogating
the fundamental or low-lying vibrational energy levels of the compound
molecules. Amongst the available prevailing label-free techniques, coherent
Raman scattering has the distinguishing features of high spatial resolution
down to 200 nm and three-dimensional sectioning. However, combining fast
imaging speed and identification of multiple - and possibly unexpected-
compounds remains challenging: existing high spectral resolution schemes
require long measurement times to achieve broad spectral spans. Here we
overcome this difficulty and introduce a novel concept of coherent anti-Stokes
Raman scattering (CARS) spectro-imaging with two laser frequency combs. We
illustrate the power of our technique with high resolution (4 cm-1) Raman
spectra spanning more than 1200 cm-1 recorded within less than 15 microseconds.
Furthermore, hyperspectral images combining high spectral (10 cm-1) and spatial
(2 micrometers) resolutions are acquired at a rate of 50 pixels per second.
Real-time multiplex accessing of hyperspectral images may dramatically expand
the range of applications of nonlinear microscopy.Comment: 8 pages, 3 figure
Ultraviolet dual comb spectroscopy: a roadmap
Dual Comb Spectroscopy proved its versatile capabilities in molecular
fingerprinting in different spectral regions, but not yet in the ultraviolet
(UV). Unlocking this spectral window would expand fingerprinting to the
electronic energy structure of matter.This will access the prime triggers of
photo-chemical reactions with unprecedented spectral resolution. In this
research article, we discuss the milestones marking the way to the first UV
dual comb spectrometer. We present experimental and simulated studies towards
UV dual comb spectroscopy, directly applied to planned absorption measurements
of formaldehyde (centered at 343 nm, 3.6 eV) and argon (80 nm, 16 eV). This
will enable an unparalleled relative resolution of up to - with a
table-top UV source surpassing any synchrotron linked spectrometer by at least
two and any grating-based UV spectrometer by up to six orders of magnitude
Cavity-enhanced dual-comb spectroscopy
The sensitivity of molecular fingerprinting is dramatically improved when placing the absorbing sample in a high-finesse optical cavity, thanks to the large increase of the effective path-length. As demonstrated recently, when the equidistant lines from a laser frequency comb are simultaneously injected into the cavity over a large spectral range, multiple trace-gases may be identified within a few milliseconds. Analyzing efficiently the light transmitted through the cavity however still remains challenging. Here, a novel approach, cavity-enhanced frequency comb Fourier transform spectroscopy, fully overcomes this difficulty and measures ultrasensitive, broad-bandwidth, high-resolution spectra within a few tens of ”s. It could be implemented from the Terahertz to the ultraviolet regions without any need for detector arrays. We recorded, within 18 ”s, spectra of the 1.0 ”m overtone bands of ammonia spanning 20 nm with 4.5 GHz resolution and a noise-equivalent-absorption at one-second-averaging per spectral element of 3 10^-12 cm^-1Hz^-1/2, thus opening a route to time-resolved spectroscopy of rapidly-evolving single-events
BROADBAND SPECTROSCOPY WITH DUAL COMBS AND CAVITY ENHANCEMENT
Author Institution: Max-Planck-Institute for Quantum Optics, 81748 Garching, Germany and Menlo Systems GmbH, 82152 Martinsried, Germany; Max-Planck-Institute for Quantum Optics, 81748 Garching, Germany; Laboratoire de Photophysique Moleculaire, CNRS, Batiment 350, Universite Paris-Sud, 91405 Orsay, France; Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan; Max-Planck-Institute for Quantum Optics, 81748 Garching, Germany and Laboratoire de Photophysique Moleculaire, CNRS, Batiment 350, Universite Paris-Sud, 91405 Orsay, FranceClassical FTIRs handle the task of massively parallel spectroscopic probing by interferometric detection. In contrast a frequency comb Fourier transform spectrometer (FC-FTS) retains the principle of combining two interferometer beams but uses two inputs from two independent sources. Thus we can offset their frequencies to facilitate multifrequency heterodyne signal processing. The advantages of this spectrometer compared with the classical FTIR include ease of operation (no cumbersome moving delay lines), speed of acquisition (18 s demonstrated), collimated long-distance propagation, possibly diffraction-limited microscopic probing, and mid infrared as well as THz operation if necessary. In a recent proof of principle experiment we have dramatically improved the sensitivity by the implementation of an enhancement cavity around the probing volume nderline{\textbf{4}} (55), January 2010}. We recorded, within 18 s, spectra of the ammonia 1.0 m overtone bands comprising 1500 spectral elements and spanning 20 nm with 4.5 GHz resolution and a noise-equivalent-absorption at one-second-averaging of 1 cmHz, thus opening a route to time-resolved spectroscopy of rapidly-evolving single-events. Since FC-FTS only needs one detector that is easily available in practically all spectral regions, it can be envisioned that cavity-enhanced FC-FTS will assume a position of dominance for the measurements of real-time ultra-sensitive spectra in the molecular fingerprint region