Acousto-optic interaction induced photonic band gaps in silicon slab waveguides

Abstract

We demonstrate that the photonic band gaps in silicon slab waveguides are generated through the acousto-optic (AO) interaction. By exciting the acoustic eigenmodes of slab waveguides, the refractive indices and interfaces of silicon slab can be modulated periodically to perturb the guided optical waves and open up the photonic band gaps. We find that the occurrence of the strong forbidden effect to form the band gaps is due to nonlinear interactions between the guided optical and acoustic modes. Using the finite-element method, we calculate the photonic band structures of TE waves and TM waves under the perturbation of the lowest three acoustic eigenmodes, respectively. The results show that the fundamental symmetric acoustic slab mode can create Bragg photonic band gaps of tunable width. With generating acoustic-wave amplitude of 1.0 % of the slab thickness, photonic band gaps from 61.58 – 61.92 THz for TE and 89.10 – 89.24 THz for TM are demonstrated. Applications include the design of optomechanical and AO devices and micro and nanolasers.