Twist and strain tuning of third harmonic generation in glass nanostrand with two sub-wavelength hollow channels

A major challenge in third harmonic generation and its converse, parametric down-conversion, is how to arrange phase matching between signals at omega and 3 omega while maintaining a high nonlinear overlap. In this Letter, we present a design consisting of a nanostrand of glass with two hollow channels. The fundamental and third harmonic modal fields, enhanced in the region between the channels, have high nonlinear overlap, while the phase-matching wavelength can be coarse-tuned by gas pressure and fine-tuned by axial strain and mechanical twist, which, remarkably, have opposite effects. The ability to adjust the phase-matching condition may facilitate efficient generation of entangled photon triplets. (C) 2021 Optical Society of America.

Automated summary

The study presents a design for efficiently generating entangled photon triplets by adjusting gas pressure, axial strain, and mechanical twist. The nanostrand of glass with two hollow channels enhances the nonlinear overlap between the fundamental and third harmonic modal fields.