184 research outputs found
Frequency comb spectroscopy
A laser frequency combs is a broad spectrum composed of equidistant narrow
lines. Initially invented for frequency metrology, such combs enable new
approaches to spectroscopy over broad spectral bandwidths, of particular
relevance to molecules. With optical frequency combs, the performance of
existing spectrometers, such as Michelson-based Fourier transform
interferometers or crossed dispersers, involving e.g. virtual imaging phase
array (VIPA) \'etalons, is dramatically enhanced. Novel types of instruments,
such as dual-comb spectrometers, lead to a new class of devices without moving
parts for accurate measurements over broad spectral ranges. The direct
self-calibration of the frequency scale of the spectra within the accuracy of
an atomic clock and the negligible contribution of the instrumental line-shape
will enable determinations of all spectral parameters with high accuracy for
stringent comparisons with theories in atomic and molecular physics. Chip-scale
frequency-comb spectrometers promise integrated devices for real-time sensing
in analytical chemistry and biomedicine. This review article gives a summary of
advances in the emerging and rapidly advancing field of atomic and molecular
broadband spectroscopy with frequency combs.Comment: Preprint version of a review article published in Nature Photonics.
27 pages, 5 figure
Photothermal effects in ultra-precisely stabilized tunable microcavities
We study the mechanical stability of a tunable high-finesse microcavity under
ambient conditions and investigate light-induced effects that can both suppress
and excite mechanical fluctuations. As an enabling step, we demonstrate the
ultra-precise electronic stabilization of a microcavity. We then show that
photothermal mirror expansion can provide high-bandwidth feedback and improve
cavity stability by almost two orders of magnitude. At high intracavity power,
we observe self-oscillations of mechanical resonances of the cavity. We explain
the observations by a dynamic photothermal instability, leading to parametric
driving of mechanical motion. For an optimized combination of electronic and
photothermal stabilization, we achieve a feedback bandwidth of kHz and a
noise level of m rms
Holographic recording of laser-induced plasma
We report on a holographic probing technique that allows for measurement of free-electron distribution with fine spatial detail. Plasma is generated by focusing a femtosecond pulse in air. We also demonstrate the capability of the holographic technique of capturing the time evolution of the plasma-generation process
Mid-infrared frequency combs
Laser frequency combs are coherent light sources that emit a broad spectrum
consisting of discrete, evenly spaced narrow lines, each having an absolute
frequency measurable within the accuracy of an atomic clock. Their development,
a decade ago, in the near-infrared and visible domains has revolutionized
frequency metrology with numerous windfalls into other fields such as astronomy
or attosecond science. Extension of frequency comb techniques to the
mid-infrared spectral region is now under exploration. Versatile mid-infrared
frequency comb generators, based on novel laser gain media, nonlinear frequency
conversion or microresonators, promise to significantly expand the tree of
applications of frequency combs. In particular, novel approaches to molecular
spectroscopy in the fingerprint region, with dramatically improved precision,
sensitivity, recording time and/or spectral bandwidth may spark off new
discoveries in the various fields relevant to molecular sciences
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