Frequency conversion of structured light

TL;DR

This paper demonstrates the coherent frequency conversion of structured light beams from near-infrared to visible wavelengths using sum-frequency generation in a periodically poled lithium niobate crystal, preserving their phase and intensity profiles.

Contribution

It introduces a method for frequency converting structured light while maintaining its phase and intensity structure, enabling new applications in microscopy and quantum information.

Findings

Successful conversion of structured light from 803nm to 527nm

Preservation of phase and intensity profiles after conversion

Verification of coherence using mode-projection technique

Abstract

We demonstrate the coherent frequency conversion of structured light, optical beams in which the phase varies in each point of the transverse plane, from the near infrared (803nm) to the visible (527nm). The frequency conversion process makes use of sum-frequency generation in a periodically poled lithium niobate (ppLN) crystal with the help of a 1540-nm Gaussian pump beam. We perform far-field intensity measurements of the frequency-converted field, and verify the sought-after transformation of the characteristic intensity and phase profiles for various input modes. The coherence of the frequency-conversion process is confirmed using a mode-projection technique with a phase mask and a single-mode fiber. The presented results could be of great relevance to novel applications in high-resolution microscopy and quantum information processing.