Ridge Resonance: A new Resonance Phenomenon for Silicon Photonics Harnessing Bound States in the Continuum

We present a new resonant behavior based on bound states in the continuum in a guided wave silicon platform. The continuum has the form of a collimated beam of light which is confined vertically in a TE mode of a silicon slab. The bound state is a discrete TM mode of a ridge on the silicon slab. The coupling between the slab and ridge modes results in a single sharp resonance at the wavelength where they phase match. We experimentally demonstrate this phenomenon on a silicon photonic chip using foundry compatible parameters and interface it on-chip to standard single mode silicon nanowire waveguides. The fabricated chip exhibits a single sharp resonance near 1550 nm with a line width of a few nanometer, an extinction ratio of 25 dB and a thermal stability of 19.5 pm/C. We believe that this is the first demonstration of bound states in the continuum resonance realized using guided wave components.