Terahertz amplification and lasing in pump-probe experiments with hyperbolic polaritons in -BN
Phys. Rev. B 113, 104312 – Published 23 March, 2026
DOI: https://doi.org/10.1103/3qdw-rm3t
Abstract
We theoretically study terahertz pump-probe experiments in from the perspective of Floquet optical materials and photonic time crystals. The anisotropic nature of this material results in a large separation of frequencies of in-plane and out-of-plane optical phonons and leads to several branches of phonon-polariton excitations. We consider a slab of finite thickness pumped at the frequency of middle polaritons, around 25 THz. We theoretically analyze properties of the pump induced state and identify several interesting features, including possible light amplification and parametric instability at 2 THz. We relate these features to resonant pair scattering processes of polaritons excited by the pump pulse. We show that amplification/instability frequency ranges depend on both the pump intensity and the slab thickness. We point out that this setup can be utilized to strongly enhance optical nonlinearities at terahertz frequencies. Richness and tunability of this system suggest that it holds promise for practical applications in terahertz technology.
