Terahertz (THz) photonics provides unique capabilities for probing and controlling material properties on ultrafast timescales. THz radiation directly couples to low-energy excitations such as carrier transport, phonons, and collective electronic modes, while high-field excitation enables access to nonlinear and non-equilibrium regimes of light-matter interaction. These properties make THz photonics a powerful tool for investigating advanced materials and fundamental physical processes.
In this seminar I will present advances in the generation of high-field THz radiation using filament-based and nonlinear optical approaches, enabling significant enhancement of field strength and access to extreme electromagnetic regimes. These capabilities have been applied to investigate ultrafast carrier dynamics and nonlinear optical responses in metamaterials and graphene, as well as light-matter interaction in layered magnetic quantum materials such as CrSBr. Building on these capabilities, THz probing can be extended to the nanoscale using scattering-type near-field optical microscopy (s-SNOM), which enables spatial resolution beyond the diffraction limit. This approach allows direct visualization of localized electromagnetic modes and ultrafast dynamics with nanometer-scale resolution. Examples include nanoscale imaging of THz-driven plasmon propagation in the linear regime, as well as THz-induced ferroelectric switching driven by strong localized field enhancement at the tip. Together, these results show how high-field excitation and nanoscale near-field probing form complementary capabilities within terahertz photonics, enabling access to nonlinear regimes while providing nanoscale resolution of material dynamics. This framework provides versatile tools for investigating complex materials and advancing nanoscale photonic sensing.