All-optical switching at the Fano resonances in subwavelength gratings with very narrow slits

We theoretically discuss all-optical switching at the Fano resonances of subwavelength gratings made of a chalcogenide glass (As2S3). Particular attention is devoted to the case in which the grating possesses extremely narrow slits (channels ranging from a similar to 10nm to a similar to 40nm). The remarkable local field enhancement available in these situations conspires to yield low-threshold switching intensities (similar to 50MW/cm(2)) at telecommunication wavelengths for extremely thin (d similar to 200nm) gratings when a realistic value of the As2S3 cubic nonlinearity is used. (C) 2011 Optical Society of America