Fano resonances in ultracompact waveguide Fabry-Perot resonator side-coupled lossy nanobeam cavities

We propose and demonstrate experimentally an ultracompact resonant system exhibiting sharp asymmetric Fano-resonance, in which a tiny photonic crystal nanobeam cavity is laterally coupled to a waveguide Fabry-Perot resonator. Under the presence of cavity intrinsic loss, we find that the system produces sharper and higher extinction ratio Fano resonance spectra only if appropriate phase is selected. The whole device (∼6 μm2) is implemented on silicon on insulator platform, and experimentally we observe steep-slope Fano resonance with extinction ratio of 7.3 dB, slope above 5 dB/nm, and average insertion loss less than 1.8 dB.