Ultra-compact High Speed Plasmonic MachZehnder Modulator Utilizing Three-Waveguide Directional Couplers

In this paper we propose a high speed, low energy consumption, Mach-Zehnder interferometer modulator. Bendless three-waveguide directional couplers are employed as splitter/combiner to diminish the overall footprint while keeping the insertion loss of the structure negligible. Si-polymer-metal hybrid plasmonic waveguide is used for the Mach-Zehnder arms where the phase shift will occur. Strong confinement of the optical mode inside the hybrid plasmonic waveguide and its low group velocity propagation facilitate achieving the phase shift required for optical modulation within small propagation length. This reduces the overall length of the Mach-Zehnder modulator and therefore decreases the resistor-capacitor time constant of the structure which in turn increases the achievable modulation speed. Based on our calculations proposed modulator shows high modulation speed of ~1.1 THz, very low energy consumption of ~12 fJ/bit, and 5.5 dB loss at drive voltage of ±3 V (which is applied in push-pull scheme). Apart from electrodes, the overall footprint of modulator is ~1.5×37 μm2. Compared to conventional electro-optical modulators the proposed structure offers very high modulation speed and low energy consumption with compact overall foot-print.