Ultrasensitive Force Sensing with Nanospheres in an Optical Standing Wave Trap
AuthorCunningham, Mark Samuel
AdvisorGeraci, Andrew A.
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This thesis details the experimental progress developing a state-of-the-art neutral force sensor using an optically levitated nano-sphere. Trapping 300 nm diameter fused silica spheres using a dual beam optical standing wave trap, we have experimentally reported a force sensitivity of 1.63 0:37aN=Hz1=2. Also we have measured the heating rate of the nano-spheres at high vacuum, and we have experimentally explored the nano-sphere dynamics to optimize the trap stability at pressures on the order of 10−6 mbar. At this pressure, with averaging times on the order of 105 s, we have demonstrated force sensing at 5.8 1.3 zN.The experimental merit of this ultra-sensitive neutral force sensor is to test for non-Newtonian gravity-like forces on the micron scale. In order to push our sensitivities even further toward this goal, we have developed a second optical standing wave trap system. Using two laser frequencies, 1596 nm and 1064 nm, incident on a single hemispherical optical cavity, we have successfully trapped nano-spheres inside the optical standing wave trap. In this thesis we outline the frequency stabilization system, the optical cavity, and experimental progress in overlapping both optical standing wave traps. We will outline further improvements that can and are being made to improve the system. Also included is an outline of our data analysis using Matlab to show nano-sphere displacement and force measurement.