Quasi-BIC resonant enhancement of dynamically controlled radiative rate in two-dimensional molybdenum diselenide for active metasurface antennas

We report on the electronic modulation of the phase and amplitude of scattered light from monolayer molybdenum diselenide (MoSe₂) coupled to quasi bound states in the continuum (BIC) modes in nanoscale AlGaAs resonators. Fermi level control via electronic gating of carrier density gives rise to dynamic phase and amplitude tunability of the reflected light. Our structure exploits the large excitonic reflectivity dominated by radiative emission in MoSe₂ at low temperatures. By measuring the gate-dependent tuning of the reflectivity of MoSe₂ at the A exciton emission wavelength, we can develop a model for the change in the complex dielectric function. We then enhance the emission rate and linewidth of monolayer MoSe₂ by integration with a metasurface comprised of subwavelength AlGaAs cylinders that support high quality factor quasi-BIC modes. This resonant structure is based on a cylinder that utilizes the destructive interference between optical modes to obtain a significant enhancement in the quality factor of the cavity. Gate tunable MoSe₂ monolayers coupled to high Q resonators thus allow us to electronically modulate the phase and amplitude of the reflected light and is a potential candidate for visible frequency active antenna elements comprising a gate-tunable metasurface.