Phase conjugation of evanescent waves has been demonstrated using near-field optics. Sergey I.

Phase conjugation of evanescent waves has been demonstrated using near-field optics. Sergey I. Bozhevolnyi and others at the University of Aalborg (Denmark) used combined degenerate four-wave mixing in an iron-doped lithium niobate crystal with an external-reflection scanning near-field optical microscope to observe near-field components of evanescent optical fields. Although phase-conjugation of evanescent waves has been described theoretically, previous technologies did not allow imaging of the near-field. Using a 10-mW, 633-nm laser, the researchers observed phase-conjugated light reach powers of 0.1 nm in a 180-nm-wide spot image. A phase-conjugating near-field device may be useful for localized spectroscopy and fluorescence imaging experiments. (Opt. Lett. 19(20), 15 Oct. 1994, p. 1603)