Light correcting light with nonlinear optics

TL;DR

This paper introduces a novel nonlinear optics method using difference frequency generation to correct distortions in structured light without prior measurement, enhancing imaging, sensing, and communication capabilities.

Contribution

The authors demonstrate a measurement-free, nonlinear optical technique for correcting structured light distortions, including complex modes like OAM, without prior characterization.

Findings

Effective correction of various aberrations in structured light

Minimal crosstalk in OAM-based communication channels

Potential for measurement-free error correction in classical and quantum optics

Abstract

Structured light, where complex optical fields are tailored in all their degrees of freedom, has become highly topical of late, advanced by a sophisticated toolkit comprising both linear and nonlinear optics. Removing undesired structure from light is far less developed, leveraging mostly on inverting the distortion, e.g., with adaptive optics or the inverse transmission matrix of a complex channel, both requiring that the distortion is fully characterised through appropriate measurement. Here we show that distortions in spatially structured light can be corrected through difference frequency generation in a nonlinear crystal without any need for the distortion to be known. We demonstrate the versatility of our approach by using a wide range of aberrations and structured light modes, including higher-order orbital angular momentum (OAM) beams, showing excellent recovery of the original undistorted field. To highlight the efficacy of this process, we deploy the system in a prepare-and-measure communications link with OAM, showing minimal crosstalk even when the transmission channel is highly aberrated, and outline how the approach could be extended to alternative experimental modalities and nonlinear processes. Our demonstration of light correcting light without the need for measurement opens a new approach to measurement-free error correction for classical and quantum structured light, with direct applications in imaging, sensing and communication