Design of a Nonlinear Plasmonic Coupler with High Coupling Efficiency over All Optical Communication Bands

There are two important issues in the design of optical devices and in special in optical couplers; down scaling and loss reduction. In this paper, a nonlinear plasmonic directional coupler consisting of two MIM (metal- insulator- metal) waveguides is proposed. In order to reduce the coupling length, part of the waveguides structure is designed in the shape of a trapezoid. Numerical analysis using finite-difference time-domain method shows that the coupling length of this scheme is 510nm for the input power of 100W/µm and at the wavelength of 1310nm. Also, the proposed coupler exhibits the coupling efficiency of more than 80% for the input power of 100W/µm over all the optical communication bands (1260-1675nm). The other property of this coupler is being able to control the output power which is the advantage of using the nonlinear waveguides.