917 research outputs found
Experimental control of pattern formation by photonic lattices
We study the control of modulational instability and pattern formation in a nonlinear dissipative feedback
system with a periodic modulation of the material refractive index. We use a one-dimensional photonic lattice
in a single-mirror feedback configuration and identify three mechanisms for pattern control: bandgap
suppression of instability modes, periodicity induced pattern modes, and orientational pattern control.The authors acknowledge the support of the
Conseil RĂ©gional de Lorraine, the bilateral FrenchAustralian
Science and Technology program, and the
Australian Research Council through Discovery
projects
Spatial phase dislocations in femtosecond laser pulses
We show that spatial phase dislocations associated with optical vortices can be embedded in femtosecond laser beams by computer-generated holograms, provided that they are built in a setup compensating for the introduced spatial dispersion of the broad spectrum. We present analytical results describing two possible arrangements: a dispersionless 4 setup and a double-pass grating compressor. Experimental results on the generation of optical vortices in the output beam of a 20 fs Ti:sapphire laser and the proof-of-principle measurements with a broadband-tunable cw Ti:sapphire laser confirm our theoretical predictions.This research was partially supported by the National
Science Fund (Bulgaria), under contract F-1303/2003, and
the Australian Research Council
Magneto-optical response enhanced by Mie resonances in nanoantennas
Control of light by an external magnetic field is one of the important
methods for modulation of its intensity and polarisation. Magneto-optical
effects at the nanoscale are usually observed in magnetophotonic crystals,
nanostructured hybrid materials or magnetoplasmonic crystals. An indirect
action of an external magnetic field (e.g. through the Faraday effect) is
explained by the fact that natural materials exhibit negligible magnetism at
optical frequencies. However, the concept of metamaterials overcome this
limitation imposed by nature by designing artificial subwavelength meta-atoms
that support a strong magnetic response, usually termed as optical magnetism,
even when they are made of nonmagnetic materials. The fundamental question is
what would be the effect of the interaction between an external magnetic field
and an optically-induced magnetic response of metamaterial structures. Here we
make the first step toward answering this fundamental question and demonstrate
the multifold enhancement of the magneto-optical response of nanoantenna
lattices due to the optical magnetism.Comment: 7 pages, 5 figure
Two-photon absorption properties of commercial fused silica and germanosilicate glass at 264 nm
Using high-intensity femtosecond pulses at lambda=264 nm, we have measured the two-photon absorption (TPA) coefficient in three fused silica samples Suprasil, Herasil, Infrasil (Heraeus) and in 3.5 mol % Ge-doped fused silica. While in fused silica samples the TPA coefficient value is about 2x10(-11) cm/W, in germanosilicate glass it equals (42+/-3)x10(-11) cm/W. (C) 2002 American Institute of Physics. (DOI: 10.1063/1.1448387
Nonlinear Bloch-wave interaction and Bragg scattering in optically-induced lattices
We study, both theoretically and experimentally, the Bragg scattering of
light in optically-induced photonic lattices and reveal the key physical
mechanisms which govern nonlinear self-action of narrow beams under the
combined effects of Bragg scattering and wave diffraction, allowing for
selecting bands with different effective dispersion.Comment: 4 pages, 6 figure
Broadband adiabatic light transfer in optically induced waveguide arrays
We demonstrate experimentally the broadband and adiabatic light transfer in coupled waveguides based on multiple stimulated Raman adiabatic passage. Our experimental platform utilizes planar-type reconfigurable optically induced waveguide arrays and allows for efficient and robust transfer of light from an input waveguide over multiple states (up to nine) to an output waveguide. The same waveguide structures are tested for two propagation wavelengths separated by more than 200 nm, proving the achromaticity of the transfer process
Improved Orbital Parameters And Transit Monitoring For HD 156846b
HD 156846b is a Jovian planet in a highly eccentric orbit (e = 0.85) with a period of 359.55 days. The pericenter passage at a distance of 0.16 AU is nearly aligned to our line of sight, offering an enhanced transit probability of 5.4% and a potentially rich probe of the dynamics of a cool planetary atmosphere impulsively heated during close approach to a bright star (V = 6.5). We present new radial velocity (RV) and photometric measurements of this star as part of the Transit Ephemeris Refinement and Monitoring Survey. The RV measurements from the Keck-High Resolution Echelle Spectrometer reduce the predicted transit time uncertainty to 20 minutes, an order of magnitude improvement over the ephemeris from the discovery paper. We photometrically monitored a predicted transit window under relatively poor photometric conditions, from which our non-detection does not rule out a transiting geometry. We also present photometry that demonstrates stability at the millimagnitude level over its rotational timescale
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