Bidirectional subwavelength slit splitter for THz surface plasmons

We have conducted a feasibility study of a frequency splitter operating at THz frequencies, based on a bidirectional subwavelength slit simulated using two-dimensional finite difference time domain (FDTD) techniques. The near-field wave emanating from the narrow slit serves as a subwavelength-scaled excitation source. By placing two optimized grating structures on the opposite sides of the slit, the THz waves at different frequencies are guided in the two desired directions. Confinement of the optical field is illustrated for different surface structures.