Optical amplification of surface plasmon polaritons in a graphene single layer integrated with a random grating

Abstract

In this paper, we design and simulate a terahertz (THz) controllable active plasmonic waveguide structure based on a single graphene layer that is placed on a random SiC grating substrate whose grooves are filled with CaF2. Optical gain in the proposed THz active plasmonic waveguide structure is provided by the stimulated emission process in the photoexcited graphene monolayer that leads to the amplification of surface plasmon polariton (SPP) waves. We use a random grating substrate to introduce Anderson localization of the SPP waves propagating through the graphene monolayer to enhance their optical amplification at resonance frequencies in which more amplification occurs due to multi-scattering and interference effects. It is shown that the input SPP wave can be amplified by 130 times at resonance frequencies of the random system. Significant amplification occurs only for frequencies that are equal to the resonance frequencies corresponding to the passive structure and are located within the gain bandwidth of graphene. The effects of depth and width of filled grooves on the amplification characteristics are also investigated. Furthermore, we show that increasing the ambient temperature by 30 K can reduce the output intensity by a factor of 12. This property of the proposed graphene-based THz plasmonic waveguide structure makes it useful in temperature sensing applications and on/off switchable laser devices.