We present a compact, all solid-state THz confocal microscope operating at 0.30 THz that achieves super-resolution by using the knife-edge scan approach. In the final reconstructed image, a lateral resolution of 60 μm ≈ λ/17 is demonstrated when the knife-edge is deep in the near-field of the sample surface. When the knife-edge is lifted up to λ/4 from the sample surface, a certain degree of super-resolution is maintained with a resolution of 0.4 mm, i.e. more than a factor 2 if compared to the diffraction-limited scheme. The present results open an interesting path towards super-resolved imaging with in-depth information that would be peculiar to THz microscopy systems.
In this paper we describe recent progress in the study of scale-free optical propagation in super-cooled nonergodic
ferroelectrics. Our experimental and theoretical findings indicate that a regime can be found in which
diffusion-driven photorefractive effects can fully annul the diffraction of focused laser beams. This demonstrates
that diffraction can be systematically eliminated from an optical system and not simply compensated, with
fundamental implications for optical imaging and microscopy. The effect transfers directly from the paraxial
regime into the non-paraxial regime described by the Helmholtz Equation, and suggests a means to achieve the
propagation of super-resolved optical images. The result is a nonlinear-based metamaterial, even though the
underlying nano-structuring of the ferroelectric is random and the effect is both non-absorptive and wavelengthindependent
for a wide spectrum.