Ridge resonators with compact guided mode coupling

Ridge resonators are a recently introduced integrated photonic circuit element based on bound states in the continuum (BICs) which can produce a single, sharp resonance over a broad wavelength range with high extinction ratio. However, to excite these resonators, a broad beam of laterally unbound slab mode is required, resulting in a large device footprint, which is not attractive for integrated photonic circuits. In this contribution, we propose and numerically validate a guided-mode waveguide structure that can be analogue to the BIC-based ridge resonators. Our simulations show that the proposed guided-mode waveguide structure can produce resonances with similar characteristics, yet with a significantly reduced footprint. Furthermore, we investigate the influence of the resonator's dimensions on the bandwidth of the resonance, demonstrating that resonances with Q-factors from low to very high (> 10000) are feasible. We believe that the reduced footprint and ability to design filters systematically make the guided-mode waveguide resonators an attractive photonic circuit component with particular value for foundry fabricated silicon photonic circuits. (c) 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

This paper proposes a guided-mode waveguide structure that exhibits similar characteristics to BIC-based ridge resonators but with a significantly reduced size. The dimensions of the resonator are shown to have an influence on the bandwidth of the resonance, allowing for a wide range of achievable Q-factors. The guided-mode waveguide resonators are deemed valuable for silicon photonic circuits in terms of their reduced footprint and systematic filter design capabilities.