A Plasmonic Modulator with High Modulation Depth Based on the Dual-Control Mechanism

The dispersion relationship of plasmons can be modulated by changing the carrier density of the propagating medium, which provides a new degree of freedom for optical modulation. Traditional graphene plasmonic modulators based on carrier control mainly revolve around chemical doping or voltage control methods, but using a single method of modulation limits the optimization of modulation depth. Herein, we propose a hybrid substrate–dielectric–silicon–graphene structure, which can achieve periodic control of the carrier density in graphene through chemical doping of silicon gratings and overall control of the carrier density by applying an external voltage between the substrate and graphene. The numerical results show that the optical transmission can reach 54.6 dB when the grating length, width, period, and working wavelength are 54 nm, 30 nm, 60 nm, and 8 μm, respectively. The modulation depth of the modulator is significantly optimized by combining the above control mechanisms. This structure will have potential applications in optoelectronic sensing, optoelectronic detection, and optical modulation.