Mode-matched Fano resonances for all-optical switching applications

We introduce the concept of mode-matched Fano resonances in one-dimensional, subwavelength, diffraction gratings. These resonances are characterized by an extremely high quality (Q)-factor and lend themselves well for applications to ultra-low power, all-optical switching devices at telecommunication wavelengths. We provide examples of diffraction gratings made of a chalcogenide glass (As2S3) where, thanks to the mode-matched Fano resonances, all-optical switching is obtained at local field intensities well below the photo-darkening threshold of the material.