A proposal for low cross-talk square-lattice photonic crystal waveguide intersection utilizing the symmetry of waveguide modes

We propose an approach to construct waveguide intersections with broad bandwidth and low cross-talk for square-lattice photonic crystals. by utilizing a vanishing overlap of the propagation modes in the waveguides created by defects which support dipole-like defect modes. The finite-difference time-domain method is used to simulate the waveguide intersection created in the two-dimensional square-lattice photonic crystals. Over a bandwidth of 30 nm with the center wavelength at 1300 nm, transmission efficiency above 90% is obtained with cross-talk below -30 dB. Especially, we demonstrate the transmission of a 500-fs pulse at 1.3 Am through the intersection, and the pulse after transmission shows very little distortion while the cross-talk remains at low level meantime. (c) 2006 Elsevier B.V. All rights reserved.

Geometry parameter optimization of large cross-sectional S-shaped bent rib waveguides for silicon based optical switches

地址: Chinese Acad Sci, Inst Semicond, State Key Lab Integrated Optoelect, Beijing 100083, Peoples R China

Fabrication of 4 x 4 tapered MMI coupler with large cross section

MMI coupler with large cross section has low coupling loss between the device and fiber. However, large chip area is required. Recently proposed N x N tapered MMI coupler shows a substantial reduction in device geometry. No such kind of devices with N > 2 has yet been realized up to now. The authors have demonstrated a 4 x 4 parabolically tapered MMI coupler with large cross section that can match the SM fiber in silicon-on-insulator (SOI) technology. The device exhibits a minimum uniformity of 0.36 dB and excess loss of 3.7 dB, It represents a key component for realization of MMI-based silicon integrated optical circuit technology.

Nd3+-doped LaF3 nanoparticles with a larger emission cross-section

A series of Nd3+-doped LaF3 nanoparticles with Nd3+ concentrations from 0.5 to 10 mol% were synthesized. The fluorescence intensity and lifetime of the nanoparticles at various Nd3+ doping concentration were investigated. The nanoparticles displayed strongest fluorescence intensity at 3 mol% Nd3+ concentration. Eighty-eight percentage quantum efficiency was obtained when the Nd3+ concentration was 0.5 mol%. Optical properties of nanoparticles were studied according to Judd-Ofelt theory. A larger emission cross-section, sigma(em), for F-4(3/2) -> I-4(11/2) transition of the Nd3+ ion was obtained as 3.21 x 10(-20) cm(2), which was two times of the currently reported value. The larger emission cross-section and strong fluorescence intensity demonstrate that these nanoparticles are promising materials for laser applications. (C) 2010 Published by Elsevier B. V.

Dependence of the cross sections for Ir isotopes on the values of Qgg in the heavy ion collision

197Au were irradiated with 47 MeV/u 12C ions. Iridium was produced via the multinucleon transfer reactions in bombardments of 197Au with 12C. and was separated radiochemically from Au and the mixture of the reaction products. The γ radioactivities of Ir isotopes were measured by using a HPGe detector. The production cross sections of Ir isotopes were determined from activities of Ir isotopes at the end of bombardment and the other relative data. It has been found that the cross sections for neutron-rich iso...