Towards High-Speed Fano Photonic Switches

Fano resonances occur as a result of the interference between a discrete mode and a continuum of modes. We have realized a Fano structure using a planar indium phosphide photonic crystal membrane device, which consists of a point-defect nanocavity side-coupled to a line-defect waveguide. Compared to the traditional symmetric Lorentzian lineshape, the asymmetric Fano lineshape is characterized by having a transmission maximum and minimum in close spectral vicinity, leading to new opportunities for optical switching, lasing, sensing and narrow band filtering. Here, we present our recent work on optical switches exploiting the sharp asymmetric Fano lineshape in combination with strong carrier-induced nonlinear resonance shifts. This unique combination has enabled femtojoule per bit all-optical switching at tens of gigahertz operation speed. Focus is given to our experimental and theoretical investigations aiming at achieving faster recovery of the switches by using a p-i-n junction around the nanocavity to sweep out carriers.