Nanoscale magneto-plasmonic phase modulator based on plasmonic resonance at disk resonator side-coupled to metal–dielectric–metal waveguide

In this letter, we present that a magneto-plasmonic nano-disk resonator side-coupled to a metal–dielectric–metal waveguide can work as a magnetically controllable plasmonic phase modulator. The disk resonator can excite traveling wave resonant modes, which have a specular property quite different from ordinary standing wave resonant modes. Due to the property, there is no reflection of the incident plasmonic signal through the waveguide, even at a resonance. In addition, an output of the signal is controllable by the disk resonator parameter, such as a radius and permittivity of the resonator and a distance between resonator and waveguide. If the resonator is filled with a magneto-optical material, the output signal can also be controlled by an external magnetic field. For a moderate intensity of the external magnetic field and a distance between the resonator and the waveguide, the phase of the output signal can be shifted as much as π/4 with respect to the case without the magnetic field. The phase shift and transmission of the output signal are constantly maintained within a bandwidth of 100 GHz and the footprint of the suggested plasmonic phase modulator is 1.5 × 1.5 μm2. The suggested magnetically controllable magneto-plasmonic phase shift can find applications in nanoscale, high speed, and phase-sensitive devices such as Mach–Zehnder interferometers and plasmonic phase shift keying modulators.