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 Régional 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