Flying focus technique steers laser-induced THz generated at a large distance from filaments to the laser in the air

https://phys.org/news/2025-02-technique-laser-thz-air.html

"controls focused fs pulse group velocity, determining plasma filament's angular distribution... controls ionization velocity/ resulting THz angle, adjusting laser's ionization front where air molecules stripped of electrons... steer waves at specific angles (even backwards)...  remote THz spectroscopy analyzing materials in detail from afar, reverse secondary radiation direction producing backward THz emission"