Novel Technique to Measure μm-Scale Forces Using a Non-Linear Attractor

The gravitational force, while well-understood at large distances, has not been measured on scales below a few tens of microns.  Several theoretical arguments suggest the possibility of variations from the inverse square law at such small scales. Recently, the use of optically levitated microspheres has shown promising results as a technique to extend the experimental reach at small distances.

The source of gravitational field for these experiments has, until now, been a reciprocating linear attractor, presenting a density modulation at micron-scale distances from the optical trap.  Some of the background forces observed can be attributed to vibrations induced by the reciprocating motion and the spurious modulation of the light exiting the trap and used for detection of the microsphere position. Such modulation results from the interaction of light halos with the reciprocating attractor. Here we report on the initial efforts to implement a rotary disk attractor system. This system is expected to reduce vibrations and change or possibly improve the scattered light background, thus reducing backgrounds and allowing for a larger signal bandwidth.