Nonlinear Photon Generations from Subwavelength Whispering-Gallery-Mode Resonator.

Chen, Bo; Wu, Sizuo; Ren, Yuhao; Wang, Xuying; Wei, Dunzhao; Liu, Jin · Nano Lett · 2024

basic_science · Level V

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Abstract

The strong light localization and long photon lifetimes in whispering gallery mode (WGM) microresonators, benefiting from a high-quality (<i>Q</i>) factor and a small mode volume (<i>V</i>), could significantly enhance light-matter interactions, enabling efficient nonlinear photon generation and paving the way for exploring novel on-chip optical functionalities. However, the leakage of energy from bending losses severely limits the improvement of the <i>Q</i> factor for subwavelength WGM microresonators. Here, we demonstrated an integrated self-suspended WGM microresonator that combines external rings and bridges with a microdisk on a platform of silicon on insulator, achieving about one-hundred-fold enhancement in the <i>Q</i> factor and an ultrasmall mode volume of 2.67(/λ<i>n</i><sub>Si</sub>)<sup>3</sup> as predicted by numerical simulations. We experimentally confirmed the improved performance of the subwavelength WGM resonator with the dramatic enhancement of third-harmonic generation and second-harmonic generation on this device. Our work is anticipated to enhance light-matter interactions on small-footprint microresonators and boost the development of efficient integrated nonlinear and quantum photonics.