Spatiotemporal imaging of nonlinear optics in van der Waals waveguides

TL;DR

This paper introduces a high-resolution spatiotemporal imaging technique to analyze and optimize nonlinear optical processes in van der Waals waveguides, enabling better phase-matching and efficiency in integrated photonics.

Contribution

It develops a novel ultrafast far-field imaging method to track light propagation in vdW waveguides, facilitating systematic optimization without prior material knowledge.

Findings

Demonstrated birefringent phase-matching in MoS2 waveguides

Revealed mode profiles and losses for nonlinear optimization

Showed potential for efficient on-chip nonlinear optics

Abstract

Van der Waals (vdW) semiconductors have emerged as promising platforms for efficient nonlinear optical conversion, including harmonic and entangled photon generation. Although major efforts are devoted to integrating vdW materials in nanoscale waveguides for miniaturization, the realization of efficient, phase-matched conversion in these platforms remains challenging. To address this challenge, we develop a far-field ultrafast imaging method to track the propagation of both fundamental and harmonic waves within vdW waveguides with extreme spatiotemporal resolution. Our approach allows systematic optimization of nonlinear conversion by determining the phase-matching angles, mode profiles, and losses in waveguides without a priori knowledge of material properties. We focus on light propagation in slab waveguides of rhombohedral-stacked MoS2, an emerging vdW semiconductor with giant nonlinear susceptibility. Our results reveal that these waveguides support birefringent phase-matching, demonstrating the material's potential for efficient on-chip nonlinear optics. This work establishes spatiotemporal imaging of light propagation in waveguides as an incisive and general method to identify new materials and architectures for efficient nonlinear nanophotonics.