Stimulated Brillouin scattering (SBS) is a strong nonlinear interaction between optical and mechanical modes of nanophotonic waveguides, whereby the optical field can generate and maintain extremely strong acoustic waves. Until recently, it was believed that the high losses associated with metals would render SBS unmeasureable in plasmonic systems. However recent work has shown that the confinement of acoustic modes in metallic structures, together with strong field gradients that occur on metal-dielectric surfaces, can result in SBS gain orders-of-magnitude greater than that in dielectric waveguides. This gain scales such that it is able to overcome the intrinsic loss of some surface plasmon polariton (SPP) configurations, depending on the waveguide geometry.
Here we examine the interaction of light and sound in plasmonic systems, including the forces and scattering processes in the presence of highly-lossy optical and acoustic modes. We examine the thermal effects arising from the optical loss and show how the measured gain is determined by the CW power-handling capabilities of the plasmonic mode. We examine a range of possible waveguide geometries and establish relevant Figures of Merit for evaluating a range of realistic plasmonic waveguides, and examine how geometrical scaling affects the SBS gain in both forward (co-propagating) and backward (counter-propagating) SBS configurations. We find that SPP-driven SBS will be measureable within a broad range of waveguides, and present general design rules for measuring SBS in different material systems. Finally, we discuss the challenges and opportunities for harnessing this effect in the first experiments.