Fully tailorable integrated-optic resonators based on chirped waveguide Moiré gratings

Abstract

Integrated-optic cavity resonators, such as Fabry–Perot microcavities and microrings, are key building blocks of photonics integrated circuits and are used extensively in applications such as optical communications and microwave photonics. For a single, conventional, optical-cavity resonator, resonance peaks appear periodically in frequency and have Lorentzian shapes in nature, which generally cannot be broken. Here, we report on fully tailorable, integrated-optic resonators that allow for independent control of individual resonance or spectral peaks as regards their presence, linewidths and extinction ratios, resonant wavelengths, and shapes and bandwidths. The response shapes can be set to be Lorentzian, Gaussian-like, or square. The resonators are based on chirped waveguide Moiré gratings developed on a silicon-on-insulator platform. We also demonstrate that they can be implemented on compact Archimedean spiral shapes to have sizes comparable to microring and microdisk resonators, with no spectral degradation. The unprecedented spectral flexibility of these resonators makes them attractive for a variety of fields and will enable new avenues for exploration in relevant areas such as optical waveform synthesis and microwave photonics.