The optical transmission characteristics through gold nanoslit arrays embedded in nonlinear medium

We present the numerical investigation of the optical transmission through a periodic gold nanoslit array embedded in the Kerr type nonlinear medium by using a developed two-dimensional Finite Different Time Domain (FDTD) method. The enhanced transmission in the nonlinear structure is attributed to the collaboration of the surface plasmon resonance and the localized waveguide resonance. We show that, in a certain intensity range, with the increase of the incident intensity, the transmission resonance peaks redshift obviously, and peak values decrease firstly and then increase; with the gold film thickness and the embedded depth becoming larger, transmission resonance peaks of both types redshift significantly, and the peak number, peak value and the half peak width change obviously. The electric fields distributions for different embedded depths of the gold slits at various resonance wavelengths are simulated to illuminate the underlying physical mechanisms. It is expected that these results obtained here will help to design nonlinear subwavelength metallic grating devices.