Conventional all-optical modulators based on surface plasmon polaritons (SPPs) primarily utilize the nonlinear effect of a given material for modulation. Their performance is heavily dependent on the optical properties of the dielectric materials used and requires high pumping power. However, manipulating SPPs by controlling electron concentrations offers a material-independent approach suitable for all-optical modulators. In this paper, we propose a hybrid gold–ITO–silver block structure integrated within a Mach–Zehnder interferometer configuration to address this problem. The gold–ITO interface effectively localizes propagating SPPs. The pump light excites localized surface plasmons (LSPs) in the silver block, generating surface electric fields that modulate the electron concentration in the adjacent ITO layer. The extinction ratio is 50.8 dB when the electron concentration changes by 3.3 × 10²⁰ cm⁻³, indicating that this structure is an all-optical modulator with a high extinction ratio. This approach shows significant promise for reducing pump power and enhancing the performance of all-optical modulators.

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.

This paper proposes a compact and tunable plasmon modulator based on a metal-grating/graphene hybrid structure, aiming to overcome the critical bottlenecks of conventional modulators in terms of integration density and dynamic tunability. The device employs two metallic gratings that generate a periodic alternating electric field in the graphene when opposite voltages are applied across the two gratings, resembling an interdigitated electrode configuration. This electric field spatially modulates the carrier density in the graphene layer, forming an equivalent Bragg grating whose duty cycle and groove depth can be dynamically tuned by adjusting the voltage amplitude, thereby enabling modulation of propagating surface plasmon polaritons in graphene. The proposed modulator, based on dual-parameter control of the Bragg grating, achieves a 10 dB enhancement in maximum modulation depth over single-parameter (groove depth) modulation, with a compact footprint of 1 μm × 0.6 μm × 1 μm, a center-wavelength tuning range of 1.0 μm, and an FWHM tuning range of 0.55 μm. This compact and tunable modulator holds significant promise for applications in mid-infrared communication and integrated photonic chips.