Abstract
We numerically study silicon waveguides on silica showing that it is possible to simultaneously guide optical and acoustic waves in the technologically important silicon on insulator (SOI) material system. Thin waveguides, or fins, exhibit geometrically softened mechanical modes at gigahertz frequencies with phase velocities below the Rayleigh velocity in glass, eliminating acoustic radiation losses. We propose slot waveguides on glass with telecom optical frequencies and strong radiation pressure forces resulting in Brillouin gains on the order of 500 and 50 000 W−1m−1 for backward and forward Brillouin scattering, respectively.
Highlights
We numerically study silicon waveguides on silica showing that it is possible to simultaneously guide optical and acoustic waves in the technologically important silicon on insulator (SOI) material system
We propose slot waveguides on glass with telecom optical frequencies and strong radiation pressure forces resulting in Brillouin gains on the order of 500 and 50 000 W−1m−1 for backward and forward Brillouin scattering, respectively
Just as a beam can be made compliant if made thin, thin silicon strips or fins on glass can be made to confine mechanics despite bulk silica’s low sound velocity
Summary
Tight confinement of the fin flexural modes to the silicon causes the symmetric and antisymmetric supermodes of the slot structure to be nearly degenerate even at spacings below 100 nm, since very little acoustic coupling occurs through the glass. For these dimensions, the waveguide has a single, TM-like mode in the telecom C-band.
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