Enhanced Raman Scattering by Quasi-phase-matched Processes in ax^（2） Photonic Crystal

An intense comb-shaped Raman spectra were obtained from a two-dimensional nonlinear x（2） photonic crystal - a hexagonally poled LiTaO3 crystal with lattice parameter 9 micros. The lowest Raman shift was down to 2 cm^-1 and the order of anti-stokes and stokes signals both achieved 11. The novel Raman spectra were mediated first by intense phonon-polariton fields, which were driven through the quasi-phase-matched coupling between the incident dual-beam both from an optical parametric oscillation laser, and further amplified greatly also by such quasi-phasematched nonlinear optical process. The dependence of the Raman spectra character on the wavelength and intensity of incident beams were studied in detail, which accordingly revealed information of the inelastic scattering and the elementary excitation in the nonlinear medium. These results on the other hand suggest technological importance for developing a novel Raman laser with the multi-wavelength output and a tunable frequency interval and for possible applications in quantum optics.

Generating the W States and the EPR States of Atoms in Cavity QED

We propose schemes for generating the W states and the EPR states of atoms. The schemes are based on cavity QED, and especially, on the interaction between a A-type three-level atom and two orthogonally-polarized cavity modes. The schemes also involve linear optical elements, for example, beam splitter, polarizing beam splitter, quarter wave plate, half wave plate, and single-photon detector. The schemes show that one can obtain the W states and the EPR states of atoms by detecting the output photon states.