Extremely strong‐field terahertz (THz) radiation in free space has compelling applications in nonequilibrium condensed matter state regulation, all‐optical THz electron acceleration and manipulation, THz biological effects, etc. However, these practical applications are constrained by the absence of high‐intensity, high‐efficiency, high‐beam‐quality, and stable solid‐state THz light sources. Here, the generation of single‐cycle 13.9‐mJ extreme THz pulses from cryogenically cooled lithium niobate crystals and a 1.2% energy conversion efficiency from 800 nm to THz are demonstrated experimentally using the tilted pulse‐front technique driven by a home‐built 30‐fs, 1.2‐Joule Ti:sapphire laser amplifier. The focused peak electric field strength is estimated to be 7.5 MV cm−1. A record of 1.1‐mJ THz single‐pulse energy at a 450 mJ pump at room temperature is produced and observed that the self‐phase modulation of the optical pump can induce THz saturation behavior from the crystals in the substantially nonlinear pump regime. This study lays the foundation for the generation of sub‐Joule THz radiation from lithium niobate crystals and will inspire more innovations in extreme THz science and applications.

Recent advances in terahertz (THz) absorbing materials and technology show futuristic potentials for practical applications in THz radars and telecommunications, stealth and shielding. However, the lack of versatile materials naturally working in this specific electromagnetic wave region with simultaneously featuring high absorption efficiencies, ultrabroad bandwidths, low‐costs, good stabilities, and flexibilities, is impeding the proliferation of real THz disruptive applications. Here a kind of flexible structure material, 3D nickel (Ni) skeleton, fabricated from an electroplating sintering method with irregular pore distribution makes possible the successful realization of a highly absorbing response for ultrabroadband THz waves due to the effective combination of both material and structural absorption mechanisms. 3D Ni skeletons with 90 ppi nonuniform pore‐size ranges enable >99% absorption capabilities in the frequency range of 0.5–2.0 THz independent on both the THz incidence angles and polarizations. Experimental validation of THz shielding implemented on both 100 GHz and 4.3 THz video imaging systems corroborates the highly efficient absorbing with frequency expansibility. Such capabilities are further verified on millimeter‐wave security checkers for 32–36 GHz. This prototypical demonstration lays the foundation for the next‐generation THz absorbing technology, accelerating advanced THz technologies toward practical applications.

No abstract

No abstract