77 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 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
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)
Nonlinear diffraction from a virtual beam
We observe experimentally a novel type of nonlinear diffraction in the process of two-wave mixing on a nonlinear quadratic grating. We demonstrate that when the nonlinear grating is illuminated simultaneously by two noncollinear beams, a second-harmonic diffraction pattern is generated by a virtual beam propagating along the bisector of the two pump beams. The observed diffraction phenomena is a purely nonlinear effect that has no analogue in linear diffraction
Multi-component optical solitary waves
We discuss several novel types of multi-component (temporal and spatial)
envelope solitary waves that appear in fiber and waveguide nonlinear optics. In
particular, we describe multi-channel solitary waves in bit-parallel-wavelength
fiber transmission systems for high performance computer networks, multi-colour
parametric spatial solitary waves due to cascaded nonlinearities of quadratic
materials, and quasiperiodic envelope solitons due to quasi-phase-matching in
Fibonacci optical superlattices.Comment: 12 pages, 11 figures; To be published in: Proceedings of the Dynamics
Days Asia-Pacific: First International Conference on Nonlinear Science
(Hong-Kong, 13-16 July, 1999), Editor: Bambi Hu (Elsevier Publishers, 2000
Positional Cloning of “Lisch-like”, a Candidate Modifier of Susceptibility to Type 2 Diabetes in Mice
In 404 Lepob/ob F2 progeny of a C57BL/6J (B6) x DBA/2J (DBA) intercross, we mapped a DBA-related quantitative trait locus (QTL) to distal Chr1 at 169.6 Mb, centered about D1Mit110, for diabetes-related phenotypes that included blood glucose, HbA1c, and pancreatic islet histology. The interval was refined to 1.8 Mb in a series of B6.DBA congenic/subcongenic lines also segregating for Lepob. The phenotypes of B6.DBA congenic mice include reduced β-cell replication rates accompanied by reduced β-cell mass, reduced insulin/glucose ratio in blood, reduced glucose tolerance, and persistent mild hypoinsulinemic hyperglycemia. Nucleotide sequence and expression analysis of 14 genes in this interval identified a predicted gene that we have designated “Lisch-like” (Ll) as the most likely candidate. The gene spans 62.7 kb on Chr1qH2.3, encoding a 10-exon, 646–amino acid polypeptide, homologous to Lsr on Chr7qB1 and to Ildr1 on Chr16qB3. The largest isoform of Ll is predicted to be a transmembrane molecule with an immunoglobulin-like extracellular domain and a serine/threonine-rich intracellular domain that contains a 14-3-3 binding domain. Morpholino knockdown of the zebrafish paralog of Ll resulted in a generalized delay in endodermal development in the gut region and dispersion of insulin-positive cells. Mice segregating for an ENU-induced null allele of Ll have phenotypes comparable to the B.D congenic lines. The human ortholog, C1orf32, is in the middle of a 30-Mb region of Chr1q23-25 that has been repeatedly associated with type 2 diabetes
Group-velocity-matched multistep cascading in nonlinear photonic crystals
We demonstrate that simultaneous phase- and group-velocity-matched cascaded parametric processes can be achieved in two-dimensional quadratic nonlinear photonic crystals by proper matching of noncollinear processes with front tilting of the fundamental pulse. We present examples of cascaded third- and fourth-harmonic generation in a poled LiNbO3 planar structure.The authors acknowledge the support of the Australian
Research Council
- …