Plasmonic phase modulator based on novel loss-overcompensated coupling between nanoresonator and waveguide.

We present that surface plasmon polariton, side-coupled to a gain-assisted nanoresonator where the absorption is overcompensated, exhibits a prominent phase shift up to π maintaining the flat unity transmission across the whole broad spectra. Bandwidth of this plasmonic phase shift can be controlled by adjusting the distance between the plasmonic waveguide and the nanoresonator. For a moderate distance, within bandwidth of 100 GHz, the phase shift and transmission are constantly maintained. The plasmonic phase can be shift-keying-modulated by a pumping signal in the gain-assisted nanoresonator. A needed length in our approach is of nanoscale while already suggested types of plasmonic phase modulator are of micrometer scale in length. The energy consumption per bit, which benefits from the nano size of this device, is ideally low on the order of 10 fJ/bit. The controllable plasmonic phase shift can find applications in nanoscale Mach-Zehnder interferometers and other phase-sensitive devices as well as directly in plasmonic phase shift keying modulators.