Diffraction Interference Induced Superfocusing in Nonlinear Talbot Effect

TL;DR

This paper introduces a novel super-focusing technique using diffraction interference in the nonlinear Talbot effect, achieving sub-wavelength focusing without evanescent waves or apertures, and experimentally realizes a 60-year-old super-resolution proposal.

Contribution

It presents the first experimental demonstration of diffraction interference induced superfocusing in the nonlinear Talbot effect, surpassing traditional diffraction limits.

Findings

Achieved focusing size less than λ_pump/8

Observed periodic second-harmonic sub-diffracted spots

First experimental realization of a super-resolution concept from 60 years ago

Abstract

We report a simple, novel sub-diffraction method, i.e. diffraction interference induced super-focusing in second-harmonic (SH) Talbot effect, to achieve focusing size of less than {\lambda}_pump/8 without involving evanescent waves or sub-wavelength apertures. By tailoring point spread functions with Fresnel diffraction interference, we observe periodic SH sub-diffracted spots over a hundred of micrometers away from the sample. Our demonstration is the first experimental realization of the proposal by Toraldo Di Francia pioneered 60 years ago for super-resolution imaging.