Optical modulation in photonic band gap structures by surface acoustic waves

We investigate theoretically the modulation of light beams in photonic band gap (PBG) structures by surface acoustic waves (SAWs). In these structures, the propagation of light beams can be actively controlled through an external acoustic stimulus. We have extended the mathematically rigorous transfer matrix method to calculate the light flow in PBG structures subjected to the spatial- and time-dependent dielectric function modulation induced by the SAW. The calculational procedure, which applies for SAWs with a frequency much smaller than that of the light, is employed to determine the transmission spectra of a one-dimensional Bragg stack with a cavity and that of a two-dimensional GaAs PBG structure with periodic air holes. We demonstrate that these two structures can be configured as an on∕off optical switch with very high contrast ratios and, in the two-dimensional case as an efficient wavelength-tunable optical filter.