Dynamic Mechanical Control of Gap Plasmons

Active photonic metasurfaces control the amplitude and phase of light over a surface and allow for dynamic and total light field manipulation. Such metasurfaces could be broadly applied to many fields such as LiDAR, AR/VR and medical sensing. Over recent years, there has been an expanded effort to improve dynamic nanophotonic devices by employing a variety of physical phenomena that modulate the interaction of light with sub-wavelength components. Mechanical modulation techniques offer high promise due to their ability to alter the optical permittivity over the surface to a greater extent than any other modulation technique. However, the mechanical actuation of dense arrays of nanoscale structures has proven to be exceedingly difficult. Here, we demonstrate mechanical modulation of the gaps between plasmonic nanoparticles and a metallic surface. This is achieved through the deformation of a compliant gap filler. Plasmonic gaps confine light to nanometer sized regions, allowing for small movements to significantly modulate the optical scattering properties of structures. Further, by using acoustic waves, mechanical forces can be sculpted across a surface at a spatial frequency like that of optics and modulated with GHz level bandwidths. These aspects together provide the ability to dynamically alter large optical phase gradients across a surface at high speed and create a new class of light modulation devices.