Manipulating the frequency of terahertz signals through temporal boundaries

https://phys.org/news/2024-06-frequency-terahertz-temporal-boundaries.html

"time-varying systems' frequency conversions... temporal boundary waveguiding: variations across entire system over time, altering dispersion and different propagation modes at new frequencies... GaAs waveguide laid over thin metallic layer., top surface's THz photoexcitation altered conductivity turning bottom into parallel double-metalized waveguide, producing frequency-down-shifted THz... up-/ down-conversion switched manipulating input polarization... optoelectronics, telecommunications"