Year: 2026
Type: article
Abstract: Temporal interfaces created by abrupt refractive-index changes enable frequency conversion and underpin photonic time crystals, but bidirectional control in a single physical system remains difficult. Here we show that collisional plasma provides pressure-controlled bidirectional microwave frequency modulation. We develop a self-consistent framework coupling finite-difference time-domain electrodynamics with particle-in-cell Monte Carlo collision kinetics, avoiding a prescribed Drude permittivity for the transient plasma response. The model predicts that high gas pressure produces a redshift dominated by collisional momentum relaxation, whereas low pressure produces a blueshift driven by rapid ionization and electron-density dispersion. Experiments using a waveguide-loaded gas discharge system reproduce the pressure-dependent shift directions predicted by the simulations. These results identify gas pressure as a control parameter for time refraction in plasma and provide a microscopic framework for designing dynamic temporal photonic systems.
Source: Communications Physics
Institution: Harbin Institute of Technology
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,990
OpenAlex ID: W7221621989
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