161 research outputs found
Efficient collinear third-harmonic generation in a single two-dimensional nonlinear photonic crystal
We propose novel multi-phase-matched process that starts with generation of a
pair of symmetric second-harmonic waves. Each of them interacts again with the
fundamental wave to produce two constructively interfering third harmonic waves
collinear to the fundamental input wave.Comment: Summary of presentation at the IQEC/LAT-2002 conferenc
Monitoring ultrashort pulses by transverse frequency doubling of counterpropagating pulses in random media
The authors study experimentally the transverse second-harmonic generation of counterpropagating pulses by a quasi-phase-matching in a medium with a random ferroelectric domain structure. The authors show that this parametric process results in a direct realization of the cross correlation of two optical signals and, therefore, it can be employed for direct characterizations of ultrashort pulses including their temporal structure and pulse front tilt.The authors acknowledge the support of the Australian
Research Council
Multistep cascading and fourth-harmonic generation
We apply the concept of multistep cascading to the problem of fourth-harmonic
generation in a single quadratic crystal. We analyze a new model of parametric
wave mixing and describe its stationary solutions for two- and three-color
plane waves and spatial solitons. Some applications to the optical frequency
division as well as the realization of the double-phase-matching processes in
engineered QPM structures with phase reversal sequences are also discussed.Comment: 3 pages, 3 figure
Generation of Bessel beams by parametric frequency doubling in annular nonlinear periodic structures
We analyze the second-harmonic generation in two-dimensional
photonic structures with radially periodic domains created by poling of a
nonlinear quadratic crystal. We demonstrate that the parametric conversion
of the Gaussian fundamental beam propagating along the axis of the annular
structure leads to the axial emission of the second-harmonic field in the
form of the radially polarized first-order Bessel beam
Detection of slow atoms confined in a Cesium vapor cell by spatially separated pump and probe laser beams
proceedings of 17th International School on Quantum Electronics: Laser Physics and Applications, neesebar, bulgaria Sept 2012 edited by Tanja Dreischuh, Albena DaskalovaInternational audienceThe velocity distribution of atoms in a thermal gas is usually described through a Maxwell-Boltzman distribution of energy, and assumes isotropy. As a consequence, the probability for an atom to leave the surface under an azimuth angle θ should evolve as cos θ, in spite of the fact that there is no microscopic basis to justify such a law. The contribution of atoms moving at a grazing incidence towards or from the surface, i.e. atoms with a small normal velocity, here called "slow" atoms, reveals essential in the development of spectroscopic methods probing a dilute atomic vapor in the vicinity of a surface, enabling a sub-Doppler resolution under a normal incidence irradiation. The probability for such "slow" atoms may be reduced by surface roughness and atom-surface interaction. Here, we describe a method to observe and to count these slow atoms relying on a mechanical discrimination, through spatially separated pump and probe beams. We also report on our experimental progresses toward such a goal
Spatial Optical Solitons due to Multistep Cascading
We introduce a novel class of parametric optical solitons supported
simultaneously by two second-order nonlinear cascading processes,
second-harmonic generation and sum-frequency mixing. We obtain, analytically
and numerically, the solutions for three-wave spatial solitons and show that
the presence of an additional cascading mechanism can change dramatically the
properties and stability of two-wave quadratic solitary waves.Comment: 6 pages, 4 figure
Generation of the second-harmonic Bessel beams via nonlinear Bragg diffraction
We generate conical second-harmonic radiation by transverse excitation of a
two-dimensional annular periodically-poled nonlinear photonic structure with a
fundamental Gaussian beam. We show that these conical waves are the far-field
images of the Bessel beams generated in a crystal by parametric frequency
conversion assisted by nonlinear Bragg diffraction.Comment: 4 pages, 5 figures. submitte
Energy exchange between two orthogonally polarized waves by cascading of two quasi-phase-matched quadratic processes
We demonstrate energy exchange between two orthogonally
polarized optical waves as a consequence of a two-color multistep
parametric interaction. The energy exchange results from cascading of two
quasi-phase-matched (QPM) second-harmonic parametric processes, and it
is intrinsically instantaneous. The effect is observed when both the type-I
(ooe) second-harmonic generation process and higher QPM order type-0
(eee) second-harmonic generation processes are phase-matched
simultaneously in a congruent periodically-poled lithium niobate crystal.
The two second-harmonic generation processes share a common secondharmonic
wave which couple the two cross-polarized fundamental
components and facilitate an energy flow between them. We demonstrate a
good agreement between the experimental data and the results of numerical
simulations
A Tabulation and Critical Analysis of the Wavelength-Dependent Dielectric Image Coefficient for the Interaction Exerted by a Surface onto a Neighbouring Excited Atom
The near-field interaction of an atom with a dielectric surface is inversely
proportional to the cube to the distance to the surface, and its coupling
strength depends on a dielectric image coefficient. This coefficient, simply
given in a pure electrostatic approach by (eps-1) / (eps+1) with eps the
permittivity, is specific to the frequency of each of the various relevant
atomic transition : it depends in a complex manner from the bulk material
properties, and can exhibit resonances connected to the surface polariton
modes. We list here the surface resonances for about a hundred of optical
windows whose bulk properties are currently tabulated. The study concentrates
on the infrared domain because it is the most relevant for atom-surface
interaction. Aside from this tabulation, we discuss simple hints to estimate
the position of surface resonances, and how uncertainties in the bulk data for
the material dramatically affect the predictions for the image coefficient. We
also evaluate the contribution of UV resonances of the material to the non
resonant part of the image coefficient.Comment: submitted (Jan. 23, 2006) to Optics Communication
Spatiotemporal toroidal waves from the transverse second-harmonic generation
We study the second-harmonic generation via transversely matched interaction of two counterpropagating
ultrashort pulses in X⁽²⁾ photonic structures. We show that the emitted second-harmonic wave attains the
form of spatially expanding toroid with the initial thickness given by the cross correlation of the pulses. We
demonstrate the formation of such toroidal waves in crystals with random ferroelectric domains as well as in
annularly poled nonlinear photonic structures.This work was supported by the Australian Research
Council and the Israeli Science Foundation
(grant 960/05)
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