Ultracompact optical switch using a single semisymmetric Fano nanobeam cavity.

We propose and theoretically analyze a generalized four-port waveguide-cavity system with a novel, to the best of our knowledge, semisymmetric Fano structure. By applying the system to a silicon-based photonic crystal nanobeam cavity (PCNC), we experimentally demonstrate an ultracompact crossbar optical switch with high drop port transmission. A low insertion loss of 1.5 dB in the drop port at the cross state is achieved comparing to the 8.5 dB insertion loss in a traditional non-Fano structure. The device is also benefited by the high quality factor and small mode volume for efficient switching and the ultracompact footprint of $ 14;\unicode{x00B5} {{\rm m}^2} $14µm in the core structure. The proposed PCNC switch shows great potential in various optical systems on chip to increase the integration and reduce energy consumption.