Optical pressure control with aperiodic nanostructured material

Abstract

The electromagnetic force on matter depends on both the geometry and the material properties, and for a contiguous material with a periodic boundary condition, the pressure is a useful metric. We present a statistical method with example results that allows the evaluation of pressure in relation to a nanostructured material arrangement formed by populating pixels within a region one wavelength on a side. The two example materials considered are gold and silicon, both in a free-space background. We find that both the magnitude of the pressure and the direction can be regulated, depending on the geometry, and these effects are related to the specifics of the internal structure resonances. Control of positive and negative pressure can be understood as being due to the total field, a superposition of the incident and scattered fields, where the structure regulates the local scattered field and hence the pressure through an integral of the resulting force density. The statistical analysis provides physical insight into how to constrain the design framework for applications. The application space includes biophysics, where information is obtained about biomolecules from force and torque measurements, cavity optomechanics related to basic science and sensing, and optical remote control and actuation, where regulation of the magnitude and direction and the possibility of materials with multiple functionalities provide new opportunities.