Tunable resonant leaky mode silicon-on-insulator photonic devices

Abstract

The objective of this paper is to present MEMS-tunable leaky-mode resonance elements. With focus on the silicon-oninsulator (SOI) materials system, the paper provides computed results elucidating the nature of resonant leaky modes associated with periodic refractive-index lattices such as gratings and photonic crystals. Introductory examples demonstrate the general features of the basic guided-mode resonance effect and the resulting externally measurable diffraction efficiency. Computed Brillouin diagrams illustrate the association of the guided-mode resonance with the second stopband considering grating profile symmetry and its Fourier harmonic content controlled by the chosen fill factors. A tunable double-grating resonant leaky-mode MEMS-type element is then introduced. Significant level of tunability is demonstrated by controlling the effective fill factor and the structural symmetry as well as the effective thickness of the resonant layer. For a particular example SOI structure treated, it is shown that the resonance wavelength can be shifted by ~500 nm with a horizontal movement of ~300 nm within the 1.6-2.2 μm wavelength band. Additionally, the reflectance can be tuned from ~10^-4 to 100% with a vertical movement of ~250 nm. These results demonstrate potentially new dimensions in design of tunable optical devices.