Abstract

Silicon nitride (Si₃N₄) is emerging as the forerunner for integrated photonic microresonator devices due to its wide transparency window from 0.47 to 6.7 µm, relatively large third-order nonlinearity, and a complementary metal-oxide semiconductor compatible fabrication process that ensures low propagation losses. The advances in the Si₃N₄ platform have led to tremendous growth in the fields of optical telecommunications, spectroscopy, and astronomical instrument calibration. Traditional on-chip microresonators are waveguide ring resonators that are evanescently coupled via a bus waveguide. Recently, a paradigm shift towards on-chip Si₃N₄ microcavities based on the Fabry-Pérot resonators has emerged [1,2]. These cavities can be formed when a central waveguide has two Bragg-like reflectors on either side. One advantage of using a linear cavity is gaining extra degrees of freedom for dispersion engineering through sub-micron structuring of the reflectors. In this work, we use broadband inverse-designed reflectors [3,4] to realize high-Q on-chip linear Si₃N₄ microresonators.

© 2023 IEEE