Experimental demonstration of ultra-compact directional couplers based on silicon hybrid plasmonic waveguides

Hybrid plasmonic waveguides and directional couplers have been experimentally demonstrated. Using a direct measurement method, the propagation loss of a 170 nm wide waveguide is measured to be 0.08 dB/mu m at 1550 nm when the thickness of low-index region is 56 nm. Ultra-compact directional couplers based on such hybrid plasmonic waveguides are demonstrated with gaps of 140 nm, 185 nm, 235 nm, and 290 nm. The corresponding coupling lengths measured are 1.55 mu m, 2.2 mu m, 3.2 mu m, and 4.8 mu m, respectively, which are in very good agreement with the simulations. These ultra-compact devices can be potentially used in future ultra-dense photonic integrated circuits. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729018]