Time-reversing a monochromatic subwavelength optical focus by optical phase conjugation of multiply-scattered light

摘要

Due to its time-reversal nature, optical phase conjugation generates amonochromatic light wave which retraces its propagation paths. Here, wedemonstrate the regeneration of a subwavelength optical focus by phaseconjugation. Monochromatic light from a subwavelength source is scattered byrandom nanoparticles, and the scattered light is phase conjugated at thefar-field region by coupling its wavefront into a single-mode optical reflectorusing a spatial light modulator. Then the conjugated beam retraces itspropagation paths and forms a refocus on the source at the subwavelength scale.This is the first direct experimental realization of subwavelength focusingbeyond the diffraction limit with far-field time reversal in the opticaldomain.