Fig. 2: Numerical feasibility study of a simple SPPS experiment based on a silicon slot waveguide and a graphene ribbon.
a Sketch of the example waveguide and electric intensity distribution of the fundamental mode at 1550 nm. The red planes indicate the two considered placements of the graphene sheet. b Total SPPS power gain, quality factor (i.e., polaritonic loss), and Stokes shift (i.e., polaritonic frequency) of the two example structures and at three different combinations of temperatures as functions of the Fermi level EF. The temperatures are: T = 300 K, thermal equilibrium between phonon and electron gases (blue dash-dotted); T = 60 K, thermal equilibrium (black solid); red dashed: lattice at Tlatt = 60 K and electron gas at Tel = 160 K (red dashed) as a result of high pump powers (see “Discussion” and Supplementary Note 2). The pink- and green-shaded areas indicate whether the optical pump can or cannot drive interband transitions, leading to a high-loss and a low-loss regime for the pump and Stokes signals. At the transition, the resonant interband contribution to the ponderomotive force creates a pronounced peak in the gain. c Relative SPPS-gain figure F = G/κa as a function of the Fermi level.
