Analysis of the Brownian motion of singly trapped spheres in hollow photonic crystal cavities

We demonstrate the use of back focal plane interferometry for the measurement of the forces felt by a trapped sphere moving inside a hollow photonic crystal cavity. The presence of two trapping regimes, one of these being a back-action effect, is observable in concordance to previous observations. We also demonstrate that particle can be differentiated by size with the monitoring of the light transmitted through the access waveguide, which is modulated via the particle induce resonance shift.