Double-layer graphene-based wedge and groove SPP waveguides with ultra-long propagation length

Abstract

This study investigates long-range surface plasmon polariton (LRSPP) waveguides based on graphene in wedge and groove configurations, comprised of two graphene layers embedded in silica wedges and grooves, respectively. The finite-difference time-domain method is employed for numerical simulations. By combining coupled-mode perturbation theory with numerical results, we demonstrate the excitation of both LRSPP modes and short-range SPP modes when two wedge-shaped or two groove-shaped graphene layers are coupled. Our findings emphasize the significant advantage of the LRSPP fundamental mode, simultaneously achieving an ultra-long propagation length (∼10 μm) and an ultra-deep subwavelength confinement (∼10−7–10−6 times the diffraction-limited mode area). This novel waveguide emerges as a promising candidate for guiding mid-infrared electromagnetic waves in future photonic integrated circuits.