Control of beaming angles via a subwavelength metallic slit surrounded by grooves

We are studying a subwavelength slit in a lossy metal film illuminated by electromagnetic waves. Periodic grooves are placed on the output side surrounding the slit. Surface plasmons along the metallic surface on the output side are excited by the electromagnetic wave propagating through the slit. The grooves modulate the surface plasmons and couple them into propagation modes, which facilitates the beaming of the output field. We developed an efficient method to determine the geometric parameters of the grooves that are necessary to achieve oblique beaming at any angle between 0 and 70 degrees. We also designed a frequency splitter by setting appropriate parameters of the grooves.