Terahertz frequency conversion at plasma-induced time boundary
Abstract
We report on the frequency conversions of terahertz (THz) waves at ultrafast time boundaries created via femtosecond laser-induced air-to-plasma phase transitions. Our combined experimental and theoretical approach reveals that the abrupt change in refractive index at the ultrafast time boundaries drives both the red and blue shifts over the broadband THz spectrum due to the dispersive plasma, with distinctive amplitude variations. The present study contrasts these effects with those from spatial boundaries, highlighting the superior efficacy of temporal manipulations for spectral engineering. These findings not only deepen the understanding of light-matter interactions in time-varying media but also pave the way for innovative applications in THz technology and lay the groundwork for the observation of temporal reflection effects, photonic time crystals, and spatio-temporally modulated matter.
Cite
@article{arxiv.2507.20663,
title = {Terahertz frequency conversion at plasma-induced time boundary},
author = {Yindong Huang and Bin Zhou and Aijun Xuan and Mingxin Gao and Jing Lou and Xiaomin Qu and Zengxiu Zhao and Ce Shang and Xuchen Wang and Chao Chang and Viktar Asadchy},
journal= {arXiv preprint arXiv:2507.20663},
year = {2025}
}