32 research outputs found
Piezospectroscopic measurement of high-frequency vibrations in a pulse-tube cryostat
Vibrations in cryocoolers are a recurrent concern to the end user. They
appear in different parts of the acoustic spectrum depending on the
refrigerator type, Gifford McMahon or pulse-tube, and with a variable coupling
strength to the physical system under interest. Here, we use the
piezospectroscopic effect in rare-earth doped crystals at low temperature as a
high resolution, contact-less probe for the vibrations. With this optical
spectroscopic technique, we obtain and analyze the vibration spectrum up to
700kHz of a 2kW pulse-tube cooler. We attempt an absolute calibration based on
known experimental parameters to make our method partially quantitative and to
provide a possible comparison with other well-established techniques
Quantum memory for light: large efficiency at telecom wavelength
We implement the ROSE protocol in an erbium doped solid, compatible with the
telecom range. The ROSE scheme is an adaptation of the standard 2-pulse photon
echo to make it suitable for a quantum memory. We observe an efficiency of 40%
in a forward direction by using specific orientations of the light
polarizations, magnetic field and crystal axes
Selective optical addressing of nuclear spins through superhyperfine interaction in rare-earth doped solids
In Er:YSiO, we demonstrate the selective optical addressing of
the Y nuclear spins through their superhyperfine coupling with
the Er electronic spins possessing large Land\'e -factors. We
experimentally probe the electron-nuclear spin mixing with photon echo
techniques and validate our model. The site-selective optical addressing of the
Y nuclear spins is designed by adjusting the magnetic field strength and
orientation. This constitutes an important step towards the realization of
long-lived solid-state qubits optically addressed by telecom photons.Comment: 5 pages, 4 figures, supplementary material (3 pages
Optical memory bandwidth and multiplexing capacity in the erbium telecommunication window
We study the bandwidth and multiplexing capacity of an erbium-doped optical
memory for quantum storage purposes. We concentrate on the protocol ROSE
(Revival of a Silenced Echo) because it has the largest potential multiplexing
capacity. Our analysis is applicable to other protocols that involve strong
optical excitation. We show that the memory performance is limited by
instantaneous spectral diffusion and we describe how this effect can be
minimised to achieve optimal performance
Interlaced spin grating for optical wave filtering
Interlaced Spin Grating is a scheme for the preparation of spectro-spatial
periodic absorption gratings in a inhomogeneously broadened absorption profile.
It relies on the optical pumping of atoms in a nearby long-lived ground state
sublevel. The scheme takes advantage of the sublevel proximity to build large
contrast gratings with unlimited bandwidth and preserved average optical depth.
It is particularly suited to Tm-doped crystals in the context of classical and
quantum signal processing. In this paper, we study the optical pumping dynamics
at play in an Interlaced Spin Grating and describe the corresponding absorption
profile shape in an optically thick atomic ensemble. We show that, in Tm:YAG,
the diffraction efficiency of such a grating can reach 18.3% in the small
angle, and 11.6% in the large angle configuration when the excitation is made
of simple pulse pairs, considerably outperforming conventional gratings.Comment: 11 pages, 13 figures in Physical Review A, 201
Time reversal of light by linear dispersive filtering near atomic resonance
Based on the similarity of paraxial diffraction and dispersion mathematical
descriptions, the temporal imaging of optical pulses combines linear dispersive
filters and quadratic phase modulations operating as time lenses. We consider
programming a dispersive filter near atomic resonance in rare earth ion doped
crystals, which leads to unprecedented high values of dispersive power. This
filter is used in an approximate imaging scheme, combining a single time lens
and a single dispersive section and operating as a time reversing device, with
potential applications in radio-frequency signal processing. This scheme is
closely related to three-pulse photon echo with chirped pulses but the
connection with temporal imaging and dispersive filtering emphasizes new
features.Comment: 21 pages, 11 figure
Ultrasound modulated optical tomography in scattering media: flux filtering based on persistent spectral hole burning in the optical diagnosis window
Ultrasound modulated optical tomography (UOT) is a powerful imaging technique
to discriminate healthy from unhealthy biological tissues based on their
optical signature. Among the numerous detection techniques developed for
acousto-optic imaging, only those based on spectral filtering are intrinsically
immune to speckle decorrelation. This paper reports on UOT imaging based on
spectral hole burning in Tm:YAG crystal under a moderate magnetic field (200G)
with a well-defined orientation. The deep and long-lasting holes translate into
a more efficient UOT imaging with a higher contrast and faster imaging frame
rate. We demonstrate the potential of this method by imaging calibrated phantom
scattering gels.Comment: 4 pages, 5 figure
Rate equation reformulation including coherent excitation: application to periodic protocols based on spectral hole-burning
International audienceA large number of signal-processing protocols are based on recording a spectral pattern via spectral hole-burning in an inhomogeneously broadened absorption profile. We present a simulation method specifically designed for periodic excitation sequences leading to the creation of a spectral pattern. This method is applicable to any multi-level atomic structure. The atomic variables' coherent dynamics are solved for a single temporal excitation step. The result is expressed as an equivalent population transfer rate. This way, the whole sequence is described as a matrix product and the steady state of the system under periodic excitation is easily derived. The propagation through the atomic medium is fully decoupled from the temporal evolution. We apply this method to the engraving of a spectral grating in a large-absorption Tm:YAG sample for wideband spectral analysis
20 GHz instantaneous bandwidth RF spectrum analyzer with high time-resolution
International audienceWe report on the experimental demonstration of a multi-gigahertz bandwidth RF spectrum analyzer exhibiting a resolution below 20 MHz, based on spectral hole burning in a rare-earth ion-doped crystal. To be compatible with demanding real-time spectrum monitoring applications, our demonstrator is designed to reach a high time resolution. For this purpose, we implemented the so-called "rainbow" architecture in which the spectral components of the incoming signal are angularly separated by the crystal, and are then acquired with a pixelated photodetector. The Tm 3+ :YAG crystal is programmed with a semiconductor DFB laser which frequency scan is servo-controlled and synchronized with the angular scan of a resonant galvanometric mirror, while a high-speed camera is used to acquire the spectra. In the perspective of future implementation within a system, the crystal is cooled below 4 K with a closed-cycle cryostat. With this setup, we have been able to monitor and record the spectrum of complex microwave signals over an instantaneous bandwidth above 20 GHz, with a time resolution below 100 µs, 400 resolvable frequency components and a probability of intercept of 100 %
Strain-mediated ion-ion interaction in rare-earth-doped solids
It was recently shown that the optical excitation of rare-earth ions produces a local change of the host matrix shape, attributed to a change of the rare-earth ion's electronic orbital geometry. In this work we investigate the consequences of this piezo-orbital backaction and show from a macroscopic model how it yields a disregarded ion-ion interaction mediated by mechanical strain. This interaction scales as , similarly to the other archetypal ion-ion interactions, namely electric and magnetic dipole-dipole interactions. We quantitatively assess and compare the magnitude of these three interactions from the angle of the instantaneous spectral diffusion mechanism, and reexamine the scientific literature in a range of rare-earth doped systems in the light of this generally underestimated contribution