Resonant optical trapping and back-action effects in a hollow photonic crystal cavity

We report on the first experimental demonstration of a resonant optical trap in a two-dimensional hollow photonic crystal cavity. Resonant trapping is implemented in an optofluidic silicon chip. Individual 250 and 500 nm polystyrene particles are trapped using optical powers of the order of 100 μW. Local refractive index perturbation associated with the particle presence lead to modifications of the cavity eigenfrequency. Back-action phenomena resulting from these perturbations are investigated. In particular, the existence of two distinct trapping regimes is demonstrated.