Plasmon-enhanced four-wave mixing for superresolution applications.

We introduce a nonlinear optical approach to transform spatial information stored in evanescent waves into propagating ones: we study analytically the use of partially degenerate four-wave mixing in thin metallic film to map a band of evanescent waves at a given frequency into a propagating-wave band at a different one. The relatively low efficiency of this process is compensated by setting the pump beam, mediating this transformation, to be a surface plasmon polariton, whose field enhancement increases the nonlinear interaction strength. This setting can be utilized for nonresonant plasmon-assisted superresolution applications that support transverse-electric polarization, in contrast to linear plasmonic imaging (such as superlens) that can only transfer transverse-magnetic waves.