Vertical Engineering for Large Brillouin Gain in Unreleased Silicon-Based Waveguides

Laura Mercadé, Alexander V. Korovin, Yan Pennec, Jouni Ahopelto, Bahram Djafari-Rouhani, Alejandro Martínez (Corresponding Author)

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Strong acousto-optic interaction in high-index waveguides and cavities generally requires the releasing of the high-index core to avoid mechanical leakage into the underlying low-index substrate. This complicates fabrication, limits thermalization, reduces the mechanical robustness, and hinders large-area optomechanical devices on a single chip. Here, we overcome this limitation by employing vertical photonic-phononic engineering to drastically reduce mechanical leakage into the cladding by adding a pedestal with specific properties between the core and the cladding. We apply this concept to a silicon-based platform, due to the remarkable properties of silicon to enhance optomechanical interactions and the technological relevance of silicon devices in multiple applications. Specifically, the insertion of a thick silicon nitride layer between the silicon guiding core and the silica substrate contributes to reducing gigahertz-frequency phonon leakage while enabling large values of the Brillouin gain in an unreleased platform. We numerically obtain values of the Brillouin gain around 300(W m)-1 for different configurations, which could be further increased by operation at cryogenic temperatures. These values should enable Brillouin-related phenomena in centimeter-scale waveguides or in more compact ring resonators. Our findings could pave the way toward large-area unreleased-cavity and waveguide optomechanics on silicon and other high-index photonic technologies.
Original languageEnglish
Article number034021
JournalPhysical Review Applied
Volume15
Issue number3
DOIs
Publication statusPublished - Mar 2021
MoE publication typeA1 Journal article-refereed

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