G-s0 mode converter with lateral gold mirrors for nano-plasmonic integrated circuits

We propose a waveguide-typed plasmonic mode converter with lateral gold mirrors (LGMs) at a wavelength of 1.55 μm. The 17.5 μm-long gap-s0 mode converter (G-s0 MC) is composed of an input 4.5 μm-wide insulator-metal-insulator-metal-insulator waveguide (IMIMI-W) and an output 2.0 μm-wide metal-insulator-metal waveguide (MIM-W) with LGMs connected by a laterally tapered (LT) IMIMI-W with LGMs. The strip thicknesses of the IMIMI-Ws and MIM-W are 20 nm and 50 nm, respectively. The 12.0 μm-long LGMs with 1.5 μm thickness are located beside the LT-IMIMI-W and MIM-W. All metals in the IMIMI-Ws, MIM-W, and LGMs are designed with gold. A low-loss polymer is used for the 30 μm-thick upper and lower cladding layers. The thickness of the central insulator in both the IMIMI-Ws and MIM-W was designed to be 500 nm. The input Ss0 mode with the size of -5.9 μm x 4.8 μm is converted to the output G-s0 mode with the size of 1.1 μm x 0.5 μm. The total loss of the G-s0 MC, including conversion loss, is -6.96 dB in simulation. The proposed G-s0 MC may be potentially useful for bridging micro- to nano-plasmonic integrated circuits.