Recent Progress in Strong-field Terahertz: generation, detection, and ultrafast magnetization dynamics

In recent years, strong-field terahertz (THz) pulses have achieved substantial improvements in single-pulse energy, peak field strength, and high average power. As electromagnetic radiation, THz pulses intrinsically contain both electric- and magnetic-field components. Because the electric and magnetic fields have different physical dimensions, their numerical amplitudes should not be compared directly; the relevant distinction is instead the strength and selection rules of electric-dipole and magnetic-dipole coupling to matter. Although THz electric-field detection and applications have become increasingly mature, research on THz magnetic fields has progressed more slowly because of weak magnetic responses, which have limited the development of strong-field THz magnetic detection and magnetic manipulation. This review focuses on representative solid-state strong-field THz sources, including lithium niobate sources and spintronic THz emitters. It summarizes recent progress in these two source platforms and discusses advances in spintronic detection and magneto-optical detection. For magnetization dynamics, we explicitly distinguish direct B_THz-driven Zeeman excitation from E_THz-driven current/spin-orbit-torque processes and from purely optical excitation mechanisms. These developments are expected to advance magnetic field applications and next-generation THz spintronics.