In-Plane Photonic Crystal Devices using Fano Resonances

Nanocavity devices enabling concentration of light in a very small volume have resulted in several interesting applications over the past years. Of particular interest are the asymmetric resonance lineshapes known as Fano resonances, which result from the interference between a discrete mode of the nanocavity and a continuum of background modes. Compared to the conventional symmetric Lorentzian lineshape, asymmetric Fano lineshapes enable novel or improved device structures for use in optical switches, sensors, lasers, and narrow band filters. Herein, the use of Fano lineshapes in photonic crystal membranes for realizing various optical signal processing functionalities is reviewed. The basic theory of Fano resonances is presented, different photonic crystal Fano device geometries are discussed, the nonlinear processes empowering the devices are explained, and an overview of all-optical signal processing demonstrations based on Fano resonances is given.