Tailoring mode splitting and degeneracy in silicon triply resonant nanobeam cavities

We investigate the use of coupled silicon nanobeam cavities for achieving multiple resonances as a photonic dedicated platform for nonlinear signal processing and sensing. The transmission spectra of the triple-coupled cavities were measured, and high quality factors, up to about 80,000, have been experimentally reported. By precisely varying the positions of three cavities vertically and horizontally, evolutions of the supermodes were fully mapped, in good agreement with the simulation designs. Some specific and interesting properties such as the dark state of the system, leading to unique transmission spectra, have been clearly observed. Based on a geometrical control of the structure, the three resonances can be tuning independently, and degeneracy modes emerge in some configurations when the distance parameters are properly chosen. This triple-resonant device is expected to enable the adjustment of third-order nonlinear properties in silicon photonics, and it is also a candidate for sensing or reconfigurable and programmable photonics. (C) 2019 Optical Society of America