Numerical study of an efficient light focusing nano-coupler based on C-shaped waveguides

We present an FDTD simulation study of a new design of light focusing nano-coupler consisting of a tapered succession of C-shaped silver waveguides. Its operation is based on the use of the fundamental guided mode TE10. Thanks to the optimization of the structural design parameters, we have demonstrated numerically that this compact coupler enables a sub-wavelength light focusing with a transmission coefficient of 65% and a coupling efficiency of 77% that have higher values than the optimized designs reported in the literature. We also show that our structure is an efficient functional coupler at multiple wavelengths when used in a periodic grating as well as an isolated device. This could pave the way for the development of a new generation of metamaterials for guidance and detection applications.