Near-field optical trapping with an actively locked cavity

Abstract

This paper details the construction and performance of a resonant cavity evanescent wavetrap for the trapping and assembling of microparticles. The technique employs a low finesseresonator which incorporates total internal reflection (TIR) at the silica/water interface togenerate an evanescent field which is coherently scattered by silica microparticles present insuspension to form optically bound structures. Circulating powers of 14 W over an area of150 µm × 75 µm were generated with a 400 mW Nd:YAG source. This approach allows some degree ofcontrol over the shape of the evanescent field by locking to higher-order cavity modes.