Nanoplasmonic couplers and modulators based on metal-insulator-metal structures

We propose a "slot-to-slot" coupler to convert power between optical and metal-insulator-metal (MIM) plasmonic modes. Coupling efficiency of larger than 60% is obtained from 2D FDTD simulation. Based on this prototype, a quasi-MIM plasmonic junction is demonstrated using e-beam lithography onto an SOI substrate. The junction is formed by depositing a thin layer of gold (similar to 20 nm) on part of a dielectric slot. When probed by 1520-nm laser, coupling efficiency of 36% is achieved for a 500-nm long quasi-MIM junction. Optical modulation is under investigation by pumping the device using visible light to change the optical property of gold.