Interference-enhanced optical force by weak light fields on a levitated nanoparticle

Optically levitated nanoparticles in vacuum provide a highly sensitive platform for probing weak light-matter interactions. In this work, we present an interference-based method to amplify the optical force exerted by a weak field on a nanoscale particle trapped in an optical tweezer. By allowing the weak field to interfere with the strong trapping beam, we significantly enhance the optical force compared to the case without interference. This amplified optical force enables the detection of the weak field through the particle's motion, reaching picowatt-level sensitivity under moderate vacuum conditions. We further discuss the potential of this approach for developing an ultrasensitive, nondestructive detector of light fields and for exploring optomechanical interactions at the single-photon level.