title: Time-reversing a monochromatic subwavelength optical focus by optical phase conjugation of multiply-scattered light.
abstract: Due to its time-reversal nature, optical phase conjugation generates a monochromatic light wave which retraces its propagation paths. Here, we demonstrate the regeneration of a subwavelength optical focus by phase conjugation. Monochromatic light from a subwavelength source is scattered by random nanoparticles, and the scattered light is phase conjugated at the far-field region by coupling its wavefront into a single-mode optical reflector using a spatial light modulator. Then the conjugated beam retraces its propagation paths and forms a refocus on the source at the subwavelength scale. This is the first direct experimental realisation of subwavelength focusing beyond the diffraction limit with far-field time reversal in the optical domain.
authors.affiliation: Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea.|KAIST Institute for Health Science and Technology, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea.
authors.forename: Jongchan
authors.initials: J
authors.lastname: Park
authors.affiliation: Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea.|KAIST Institute for the NanoCentury, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea.
authors.forename: Chunghyun
authors.initials: C
authors.lastname: Park
authors.affiliation: Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea.|KAIST Institute for Health Science and Technology, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea.
authors.forename: KyeoReh
authors.initials: K
authors.lastname: Lee
authors.affiliation: Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea.|KAIST Institute for the NanoCentury, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea.
authors.forename: Yong-Hoon
authors.initials: YH
authors.lastname: Cho
authors.affiliation: Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea.|KAIST Institute for Health Science and Technology, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea.
authors.forename: YongKeun
authors.initials: Y
authors.lastname: Park