Programming of refractive functions

TL;DR

This paper introduces a novel engineered material that can arbitrarily program light refraction, allowing independent control over the output wave direction for different input directions, with applications demonstrated in the terahertz spectrum.

Contribution

It presents a new refractive function generator capable of arbitrary, wavelength-multiplexed light refraction programming using cascaded transmissive layers.

Findings

Demonstrated permutation and negative refraction functions at terahertz frequencies.

Achieved wavelength-multiplexed refractive functions within a compact material volume.

Validated designs with 3D-printed prototypes.

Abstract

Snell's law dictates the phenomenon of light refraction at the interface between two media. Here, we demonstrate arbitrary programming of light refraction through an engineered material where the direction of the output wave can be set independently for different directions of the input wave, covering arbitrarily selected permutations of light refraction between the input and output apertures. Formed by a set of cascaded transmissive layers with optimized phase profiles, this refractive function generator (RFG) spans only a few tens of wavelengths in the axial direction. In addition to monochrome RFG designs, we also report wavelength-multiplexed refractive functions, where a distinct refractive function is implemented at each wavelength through the same engineered material volume, i.e., the permutation of light refraction is switched from one desired function to another function by changing the illumination wavelength. As experimental proofs of concept, we demonstrate permutation and negative refractive functions at the terahertz part of the spectrum using 3D-printed materials. Arbitrary programming of refractive functions enables new design capabilities for optical materials, devices and systems.