Simulation of group-velocity-dependent phase shift induced by refractive-index change in an air-bridge-type AlGaAs two-dimensional photonic crystal slab waveguide

摘要

We report on a theoretical study of a refractive-index-change-(Delta-) induced phase shift enhanced by the low group velocity in an air-bridge-type AlGaAs two-dimensional (2-D) photonic crystal (PC) slab waveguide. The calculation was based on a three-dimensional finite-difference time-domain method for the design of a phase-shift arm of the 2-D PC-based symmetric Mach-Zehnder-(SMZ-) type all-optical switch. Deltan was assumed to be induced by an optical nonlinearity of InAs quantum dots embedded selectively in the phase-shift arm in the PC SMZ. By changing Deltan from 0 to -0.01 and -0.1 for an even guided mode in the triangular-lattice single-line-defect waveguide in the PC SMZ, we calculated a group-velocity-dependent phase shift as well as a band diagram and a transmission spectrum. The result showed that the phase shift is almost inversely proportional to the group velocity. Taking into account Deltan of approximately -0.001 predicted for actual InAs quantum dots, we evaluated the length of the phase-shift arm, necessary for the T phase shift in the PC SMZ, to be similar to100 mum for a group velocity of 0.031c and a lattice constant of 0.36 mum at a wavelength of similar to1.3 mum, where c is the light velocity in the vacuum. The length of the phase-shift arm was significantly reduced because of the low group velocity in spite of the small Deltan. As a result, it was found that the phase-shift arm can be designed short enough to achieve a compact ultrafast all-optical switch. (C) 2004 Optical Society of America.