192 research outputs found
A compact, multi-pixel parametric light source
The features of a compact, single pass, multi-pixel optical parametric
generator are discussed. Several hundreds of independent high spatial-quality
tunable ultrashort pulses were produced by pumping a bulk lithium triborate
crystal with an array of tightly focussed intense beams. The array of beams was
produced by shining a microlenses array with a large pump beam. Overall
conversion efficiency to signal and idler up to 30% of the pump beam has been
reported. Shot-to-shot energy fluctuation down to 3% was achieved for the
generated radiation.Comment: 11 pages, 6 figures, submitted to "Optics Communications
Space-time coupling in the up-conversion of broadband down-converted light
We investigate the up-conversion process of broadband light from parametric
down-conversion (PDC), focusing on the spatio-temporal spectral properties of
the sum-frequency generated (SFG) radiation. We demonstrate that the incoherent
component of the SFG spectrum is characterized by a skewed geometry in
space-time, which originates from a compensation between the group-velocity
mismatch and the spatial walk-off of the fundamental and the SFG fields. The
results are illustrated both by a theoretical modeling of the optical system
and by experimental measurements.Comment: 11 pages, 9 figures. arXiv admin note: text overlap with
arXiv:1308.236
Optical Wave Modes: Localized and Propagation-Invariant Wave Packets in Optically Transparent Dispersive Media
Many applications of beams and pulses of light in modern optical technology, such as in long-distance communications, and laser micromachining, deep-field microscopy, plasma-channel generation, and laser writing of waveguides, gratings, and photonic crystals (to cite only a few), will benefit heavily from the use of particle-like waves. This term refers to waves that are capable of defeating diffraction spreading and dispersion broadening induced by the host material medium, while maintaining their spatiotemporal localization along sufficiently large, ideally infinite propagation distances
Study of Through-Hole Micro-Drilling in Sapphire by Means of Pulsed Bessel Beams
Ultrashort Bessel beams have been used in this work to study the response of a 430-m-thick
monocrystalline sapphire sample to laser–matter interaction when injecting the beam orthogonally
through the whole sample thickness. We show that with a 12 Bessel beam cone angle, we are able to
internally modify the material and generate tailorable elongated microstructures while preventing
the formation of surface cracks, even in the picosecond regime, contrary to what was previously
reported in the literature. On the other hand, by means of Bessel beam machining combined with a
trepanning technique where very high energy pulses are needed, we were able to generate 100 m
diameter through-holes, eventually with negligible cracks and very low taper angles thanks to an
optimization achieved by using a 60-m-thick layer of Kapton Polyimide removable tape
Three-Dimensional Vortex Solitons in Self-Defocusing Media
We demonstrate that families of vortex solitons are possible in a bidispersive three-dimensional nonlinear Schro\ua8dinger equation. These solutions can be considered as extensions of two-dimensional dark vortex solitons which, along the third dimension, remain localized due to the interplay between dispersion and nonlinearity. Such vortex solitons can be observed in optical media with normal dispersion,
normal diffraction, and defocusing nonlinearity
Non-linear unbalanced Bessel beams: Stationary conical waves supported by nonlinear losses
Nonlinear losses accompanying Kerr self-focusing substantially impacts the
dynamic balance of diffraction and nonlinearity, permitting the existence of
localized and stationary solutions of the 2D+1 nonlinear Schrodinger equation
which are stable against radial collapse. These are featured by linear conical
tails that continually refill the nonlinear, central spot. An experiment shows
that the discovered solution behaves as strong attractor for the self-focusing
dynamics in Kerr media.Comment: 4 pages, 2 figures; experimental verification adde
Micro-Hole Generation by High-Energy Pulsed Bessel Beams in Different Transparent Materials
Micro-drilling transparent dielectric materials by using non-diffracting beams impinging orthogonally to the sample can be performed without scanning the beam position along the sample thickness. In this work, the laser micromachining process, based on the combination of picosecond pulsed Bessel beams with the trepanning technique, is applied to different transparent materials. We show the possibility to create through-apertures with diameter on the order of tens of micrometers, on dielectric samples with different thermal and mechanical characteristics as well as different thicknesses ranging from two hundred to five hundred micrometers. Advantages and drawbacks of the application of this technique to different materials such as glass, polymer, or diamond are highlighted by analyzing the features, the morphology, and the aspect-ratio of the through-holes generated. Alternative Bessel beam drilling configurations, and the possibility of optimization of the quality of the aperture at the output sample/air interface is also discussed in the case of glass
Nonlinear absorption and gain in InGaAs/GaAs quantum wells
We present a detailed study of the excitonic nonlinearities in InGaAs/GaAs multiple quantum wells based on both stationary and transient pump-and-probe transmission spectroscopy. Bleaching of the excitonic resonance and free carrier gain have been observed. A quantitative analysis of the observed nonlinearity is provided by means of a rigorous solution of the Bethe–Salpeter equation for the investigated heterostructures
Conical emission, pulse splitting and X-wave parametric amplification in nonlinear dynamics of ultrashort light pulses
The precise observation of the angle-frequency spectrum of light filaments in
water reveals a scenario incompatible with current models of conical emission
(CE). Its description in terms of linear X-wave modes leads us to understand
filamentation dynamics requiring a phase- and group-matched, Kerr-driven
four-wave-mixing process that involves two highly localized pumps and two
X-waves. CE and temporal splitting arise naturally as two manifestations of
this process
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