Dual wavelength Talbot self-imaging using facet patterned nonlinear crystals.

A method for functional patterning of facets of a nonlinear crystal using focused ion beam milling has been developed. The near-field diffraction on periodic gratings has been experimentally and theoretically studied. The periodicity of the structure enables Talbot self-imaging at the fundamental and second-harmonic frequencies simultaneously. Spatial interference patterns for both harmonic frequencies are individual ones, which can enable the higher-accuracy optical testing, coupling the radiation at both frequencies, and wavelength-division demultiplexing. The impact of the aperture effect on a Talbot carpet is discussed.

Nonlinear Raman-Nath diffraction of femtosecond laser pulses in a 2D nonlinear photonic crystal.

We study second-harmonic generation (SHG) of femtosecond laser pulses in a rectangular two-dimensional nonlinear photonic crystal (NLPC). Multiple SH beams were observed in the vicinity of the propagation direction of the fundamental beam. It has been verified that the angular positions of these beams obey the conditions of nonlinear Raman-Nath diffraction (NRND). The measured SH spectra of specific NRND orders consist of narrow peaks that experience a high-frequency spectral shift as the order grows. We derive an analytical expression for the process studied and find the theoretical results to be in good agreement with the experimental data. We estimate the enhancement factor of nonlinear Raman-Nath diffraction in 2D NLPC to be 70.

Raman-induced gratings in atomic media.

A novel type of electromagnetically induced gratings based on the Raman nonlinearity in the field of standing pump waves are proposed. Unlike electromagnetically induced absorption gratings, these gratings are based on the spatial modulation of Raman susceptibility. We present a theoretical study of the optical response of such a spatial periodically modulated three-level atomic medium. It is shown that transmission and reflection of a probe Raman wave can be simultaneously amplified in the grating. Transmission and reflection spectra can be controlled by varying the pump field intensity. The basic mechanism responsible for all-optical control of transmission and reflection in the samples of Raman driven atoms are discussed.

Switching from normal to anomalous dispersion in photonic crystal with Raman gain defect.

Propagation of a light through a one-dimensional photonic crystal containing a defect layer doped with a Raman gain medium is discussed. We demonstrate all-optically controlled switching from normal to anomalous dispersion in such a structure. A group delay for the transmitted probe (Raman) pulse is investigated. We show that the group velocity of a Raman pulse can be tuned from subluminal to superluminal by varying the intensity of the pump field.

Angular tuning of defect modes spectrum in the one-dimensional photonic crystal with liquid-crystal layer.

A one-dimensional ZrO(2)/SiO(2) photonic crystal with a 4-n -pentyl-4' -cyanobiphenyl (5CB) nematic defect layer was used to investigate the transmission spectra of light polarized parallel and perpendicular to the liquid-crystal director at different angles of incidence. The spectra of the photonic crystal were shown to split into four polarized components T(ij) at oblique incidence. When the incident angle increased, the bandgap edges and the defect modes shifted towards short wavelengths, while the amplitudes of the defect modes increased for the transverse magnetic polarization and decreased for the transverse electric polarization. The observed discrepancy between the defect mode amplitudes in the center and near the edges of the photonic bandgap was found to be related to the radiation losses inside the defect layer of a non-ideal photonic crystal. The simulated transmission spectra obtained using recurrence relations and taking into account the decay of defect modes are in good agreement with the experimental data.