  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.
