Temporal Weyl Physics and Topological Control of Direction-Selected Radiation in Anisotropic Photonic Time Crystals

TL;DR

This paper introduces temporal Weyl points in anisotropic photonic time crystals, revealing topological features that enable directional control of light-matter interactions in the time domain.

Contribution

It constructs and analyzes temporal Weyl points in anisotropic photonic time crystals, demonstrating their unique topological properties and effects on radiation control.

Findings

Robust Fermi arcs link opposite topological charges in temporal Weyl points.

Directional near-zero radiation trajectories can be achieved and tuned.

Fermi arcs suppress radiation in specific directions and frequencies.

Abstract

Anisotropic photonic time crystals, enabled by periodic temporal modulation of a uniform anisotropic medium, exhibit asymmetric momentum-bandgap structures and offer unique control over light-matter interactions. Here, we introduce and construct temporal Weyl points in APTCs within a synthetic three-dimensional space defined by two phase parameters and the quasi-frequency. The temporal response reveals robust Fermi arcs linking TWPs of opposite topological charge. Unlike spatial counterparts, these Fermi arcs emerge only after the first temporal supercell comprising multiple periods of APTCs, reflecting causality. We further show that TWPs generate a directional near-zero radiation trajectory in momentum space with tunable radiation from stationary charges embedded in APTCs, while the associated Fermi arcs robustly suppress radiation at selected directions and frequencies. Our findings establish temporal Weyl physics in photonic time crystals and uncover new opportunities for topological control of light-matter interactions through the time dimension.