Study of an active hybrid gap surface plasmon polariton waveguide with nanoscale confinement size and low compensation gain

Abstract

A silicon-based hybrid gap surface plasmon polariton (SPP) waveguide consisting of an active InP/GaInAsP/InP double heterostructure layer, a silver cladding with a rectangular bump and a gap between them is presented. Based on this waveguide, all the SPP waveguides and even the SPP components share a common planar active medium layer in the whole photonic integration circuit chip, so not only can both the waveguide structure width and the mode lateral confinement width be of nanoscale simultaneously, but optical pumping can also be easily realized for compensating the propagation loss of all the SPP waveguides and components. By means of thickening the active GaInAsP layer and thinning the gap, the threshold gain coefficient is reduced to an achievable range and the mode confinement size is dropped to the nanoscale. Numerical simulation suggests that when the gap size is 50 nm × 10 nm and the GaInAsP height is 350 nm, by adjusting the metal bump height, the effective mode area is at λ0 = 1550 nm and the full-width at half-maximum of the Poynting vector magnitude is 66 nm and the threshold gain coefficient is 158.5 cm−1 or 850.9 cm−1 for different Ag permittivities coming from two sources.