Novel Techniques to Measure Micron-Scale Gravity

The gravitational force, while understood precisely at large distances, has not been measured on scales below a few tens of microns. Recently, the use of optically levitated sensors has shown promising results as a technique to probe parameter space at these scales.

However, the sensitivity of these experiments seems currently to be limited by backgrounds. These backgrounds are inherent to current measurement schemes that rely on density-modulated attractors driven sinusoidally in close proximity to an optically-levitated dielectric microsphere to induce and measure a time-varying gravitational signal. Three limitations of this technique can be connected to the sinusoidal motion: mechanical backgrounds from the acceleration of the attractor, electrostatic backgrounds coupling to the microsphere’s permanent dipole moment, and optical backgrounds from scattered light.

One path towards eliminating these backgrounds is to use a rotating disk with various built-in density modulations. Here, I report on the efforts of understanding and implementing such a rotary attractor in our existing system. Specifically, I build a signal model using a FEM simulation which informs optimal density profiles for manufacturing, use microscopic video registration to characterize the stability of hardware, and outline the steps needed for a full implementation.