Scientists from Nankai University and the Advanced Science Research Center of City University of New York, in collaboration with Israel Institute of Technology, have discovered that anisotropic photonic time crystals (APTCs) can produce coherent radiation when a stationary charge is embedded in them. The radiation can then be amplified exponentially by coupling with the Floquet mode in the momentum band gap.
The research, titled “Stationary Charge Radiation in Anisotropic Photonic Time Crystals,” was published in Physical Review Letters. A generalized temporal transfer matrix formalism was developed to study the radiation of the stationary charge in APTCs, which manage emission features due to their reconfigurable anisotropic band structure in momentum space. The inherent anisotropic band structure of APTCs enables extreme lasing directionality, which does not require source manipulation for delicate phase matching, unlike nonresonant tunable lasers based on photonic time crystals. This research opens a new avenue to control radiation of charges in scenarios of stationary charges.