High modulation depth, ultra-compact, and tunable electro-optical modulator based on dielectric-loaded graphene-plasmonic waveguides

Abstract

In this study, we propose a novel ultra-compact, tunable electro-optical (EO) modulator based on dielectric-loaded graphene-plasmonic waveguides (DLGPW). By leveraging the exceptional optical and electrical properties of graphene, the modulator achieves high modulation depth (MD) and extinction ratio (ER) for operation in the mid-infrared (MIR) region. The device utilizes surface plasmon polaritons (SPPs) excited at the graphene-dielectric interface, enabling strong light confinement and low propagation losses. By adjusting the chemical potential of graphene through an external voltage, the refractive index of graphene is tuned, allowing for precise control over the resonant wavelength and modulation characteristics. Through detailed numerical simulations using the three-dimensional finite-difference time-domain (3D-FDTD) method, we demonstrate that the proposed modulator achieves an MD of 98.69%, an ER of 18.835 dB, and IL of 2.5 dB, with a modulation bandwidth of 1.13 THz. The ultra-compact design and compatibility with CMOS technology make the proposed modulator a promising candidate for next-generation photonic systems, particularly in applications requiring high-speed and efficient modulation in MIR spectral ranges.