Enhanced stimulated Brillouin scattering in unsuspended silicon waveguide assisted with genetic algorithms

Abstract

Stimulated Brillouin scattering (SBS), originating from the coupling between optical and acoustic waves, has been widely applied in many fields. Silicon is the most used and important material in MEMS and integrated photonic circuits. However, strong acoustic-optic interaction in silicon requires fully or partially release of the silicon core waveguide to avoid mechanical leakage into the substrate. This will not only reduce the mechanical stability and thermal conduction, but also increase the difficulties for fabrication and large-area device integration. In this paper, we propose a silicon-aluminium nitride-sapphire platform for realizing large SBS gain without suspending the waveguide. Aluminium nitride layer is used as a buffer layer to reduce the phonon leakage. This platform can be fabricated via the wafer bonding between silicon and commercial aluminium nitride-sapphire wafer. We adopt a full-vectorial model to simulated the SBS gain. Both the material loss and anchor loss of the silicon device are considered. We also apply the genetic algorithm to optimize the waveguide structure. By limiting the maximum etching step to two, we obtain a simple structure to achieve the SBS gain of 2462 𝑊⁻¹𝑚⁻¹, which is 8 times larger than the current reported result in unsuspended silicon waveguide. Our platform can enable Brillouin-related phenomena in centimetre-scale waveguide. Our findings could pave the way toward large-area unreleased opto-mechanics on silicon.

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Identifiers

ORCID for Peng Li: orcid.org/0000-0003-1828-9597

ORCID for Jun-Yu Ou: orcid.org/0000-0001-8028-6130

ORCID for Jize Yan: orcid.org/0000-0002-2886-2847

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