Dominant mode control of a graphene-embedded hybrid plasmonic resonator for a tunable nanolaser.

A graphene-embedded tunable plasmonic nanodisk resonator operating at near-infrared wavelength range is proposed, in which a certain resonant mode among multiple whispering-gallery modes (WGMs) can be selected as a dominant mode by modulating the Fermi level of the graphene. Our theoretical investigation reveals that the dominant mode selection mechanism in the proposed resonator is governed by the figure-of-merit (FOM) of the one-dimensional (1D) waveguide of the resonator's vertical structure, which is defined as a propagation length to mode size ratio. As the conductivity of the graphene changes with a gating voltage, the wavelength dependence of the FOM changes and a WGM closest to the maximum FOM wavelength is selected. Partial tuning of the selected dominant mode is incurred by the change of the effective index of the 1D waveguide. This novel mode selection mechanism of the proposed resonator can be adopted to realize an optically pumped tunable nanolaser with a wide wavelength tuning range.