Theories that attempt to unify gravity with the Standard Model or to explain the nature of dark energy suggest that gravity may deviate from the Newtonian form 1⁄r2 at micron length scales. We use mesoscopic optomechanical systems to measure sub-attonewton forces at micron length scales to test these theories.
Our current work uses optically levitated microspheres to measure gravitational interactions between masses separated by less than 20 microns. Optically levitated microspheres provide a powerful probe for short-range forces because they can be precisely controlled with optics and do not need to be mechanically coupled to the surrounding environment.
We are also exploring the use of mesoscopic optomechanical force sensors to search for other new particles and interactions. Recently, we have used optically levitated microspheres to search for millicharged particles (charged particles with much less than an electron's charge) bound in the bulk of the microspheres.
The physics of levitated microspheres turns out to be very rich and diverse, with our group recently reporting progress in controlling their rotation and possible application to gyroscopes, and the exploration of various ideas in the area of quantum sensing.