285 research outputs found
Generation of microwave radiation by nonlinear interaction of a high-power, high-repetition rate, 1064-nm laser in KTP crystals
We report measurements of microwave (RF) generation in the centimeter band
accomplished by irradiating a nonlinear KTiOPO (KTP) crystal with a
home-made, infrared laser at nm as a result of optical rectification
(OR). The laser delivers pulse trains of duration up to s. Each train
consists of several high-intensity pulses at an adjustable repetition rate of
approximately GHz. The duration of the generated RF pulses is
determined by that of the pulse trains. We have investigated both microwave-
and second harmonic (SHG) generation as a function of the laser intensity and
of the orientation of the laser polarization with respect to the
crystallographic axes of KTP.Comment: 5 pages, 5 figures, to appear in Optics Letters, vol. 38 (2013
Microwave emission by nonlinear crystals irradiated with a high-intensity, mode-locked laser
We report on the experimental investigation of the efficiency of some
nonlinear crystals to generate microwave (RF) radiation as a result of optical
rectification (OR) when irradiated with intense pulse trains delivered by a
mode-locked laser at nm. We have investigated lithium triborate (LBO),
lithium niobate (LiNbO), zinc selenide (ZnSe), and also potassium titanyl
orthophosphate (KTP) for comparison with previous measurements. The results are
in good agreement with the theoretical predictions based on the form of the
second-order nonlinear susceptibility tensor. For some crystals we investigated
also the second harmonic generation (SHG) to cross check the theoretical model.
We confirm the theoretical prediction that OR leads to the production of higher
order RF harmonics that are overtones of the laser repetition rate.Comment: accepted for publication in Journal of Optics, in pres
Cathodo- and radioluminescence of Tm:YAG and Nd:YAG in an extended wavelength range
We have studied the cathodo- and radioluminescence of Nd:YAG and of Tm:YAG
single crystals in an extended wavelength range up to m in view
of developing a new kind of detector for low-energy, low-rate energy deposition
events. Whereas the light yield in the visible range is as large as photons/MeV, in good agreement with literature results, in the
infrared range we have found a light yield photons/MeV, thereby proving that ionizing radiation is particularly
efficient in populating the low lying levels of rare earth doped crystals.Comment: submitted for publication in Journal of Luminescenc
Analogue Casimir Radiation using an Optical Para- metric Oscillator
We establish an explicit analogy between the dynamical Casimir effect and the
photon emission of a thin non-linear crystal pumped inside a cavity. This
allows us to propose a system based on a type-I optical parametric oscillator
(OPO) to simulate a cavity oscillating in vacuum at optical frequencies. The
resulting photon flux is expected to be more easily detectable than with a
mechanical excitation of the mirrors. We conclude by comparing different
theoretical predictions and suggest that our experimental proposal could help
discriminate between them.Comment: 7 pages, 2 figures, epl2 stylefile necessary to compil
Generation of microwave fields in cavities with laser-excited nonlinear media: competition between the second- and third-order optical nonlinearities
We discuss a scheme for the parametric amplification of the quantum fluctuations of the
electromagnetic vacuum in a three-dimensional microwave resonator, and report the preliminary
measurements to test its feasibility. In the present experimental scheme, the fundamental mode of
a microwave cavity is nonadiabatically perturbed by modulating the index of refraction of the
nonlinear optical crystal enclosed therein. Intense, multi-GHz laser pulses, such as those
delivered by a mode-locked laser source, impinge on the crystal to accomplish the n-index
modulation. We theoretically analyze the process of parametric generation, which is related to
the third-order nonlinear coefficient \u3c7(3) of the nonlinear crystal, and assess the suitable
experimental conditions for generating real photons from the vacuum. Second-order nonlinear
processes are first analyzed as a possible source of spurious photons in quantum vacuum
experiments when an ideal, mode-locked laser source is considered. The combination of a crystal
non-null \u3c7(2) coefficient and a real mode-locked laser system\u2014i.e. one featuring offset-fromcarrier
noise and unwanted secondary oscillations\u2014is also experimentally investigated, paving
the way for future experiments in three-dimensional cavities
A new technique for infrared scintillation measurements
We propose a new technique to measure the infrared scintillation light yield
of rare earth (RE) doped crystals by comparing it to near UV-visible
scintillation of a calibrated Pr:(LuY)AlO
sample. As an example, we apply this technique to provide the light yield in
visible and infrared range up to \SI{1700}{nm} of this crystal.Comment: submitted to NIM
Dynamical Casimir Effect in Optically Modulated Cavities
Cavities with periodically oscillating mirrors have been predicted to excite
photon pairs out of the quantum vacuum in a process known as the Dynamical
Casimir effect. Here we propose and analyse an experimental layout that can
provide an efficient modulation of the effective optical length of a cavity
mode in the near-infrared spectral region. An analytical model of the dynamical
Casimir emission is developed and compared to the predictions of a direct
numerical solution of Maxwell's equations in real time. A sizeable intensity of
dynamical Casimir emission is anticipated for realistic operating parameters.
In the presence of an external coherent seed beam, we predict amplification of
the seed beam and the appearance of an additional phase-conjugate beam as a
consequence of stimulated dynamical Casimir processes.Comment: 6 pages, 5 figure
Phase-coherent solitonic Josephson heat oscillator
Since its recent foundation, phase-coherent caloritronics has sparkled continuous interest giving rise to numerous concrete applications. This research field deals with the coherent manipulation of heat currents in mesoscopic superconducting devices by mastering the Josephson phase difference. Here, we introduce a new generation of devices for fast caloritronics able to control local heat power and temperature through manipulation of Josephson vortices, i.e., solitons. Although most salient features concerning Josephson vortices in long Josephson junctions were comprehensively hitherto explored, little is known about soliton-sustained coherent thermal transport. We demonstrate that the soliton configuration determines the temperature profile in the junction, so that, in correspondence of each magnetically induced soliton, both the flowing thermal power and the temperature significantly enhance. Finally, we thoroughly discuss a fast solitonic Josephson heat oscillator, whose frequency is in tune with the oscillation frequency of the magnetic drive. Notably, the proposed heat oscillator can effectively find application as a tunable thermal source for nanoscale heat engines and coherent thermal machines
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