Precise and ultrafast control over photo-induced charge currents across nanoscale interfaces could lead to important applications in energy harvesting, ultrafast electronics, and coherent terahertz sources. Recent studies have shown that several relativistic mechanisms, including inverse spin-Hall effect, inverse Rashba–Edelstein effect, and inverse spin-orbit-torque effect, can convert longitudinally injected spin-polarized currents from magnetic materials to transverse charge currents, thereby harnessing these currents for terahertz generation. However, these mechanisms typically require external magnetic fields and exhibit limitations in terms of spin-polarization rates and efficiencies of relativistic spin-to-charge conversion. We present a nonrelativistic and nonmagnetic mechanism that directly utilizes the photoexcited high-density charge currents across the interface. We demonstrate that the electrical anisotropy of conductive oxides RuO₂ and IrO₂ can effectively deflect injected charge currents to the transverse direction, resulting in efficient and broadband terahertz radiation. Importantly, this mechanism has the potential to offer much higher conversion efficiency compared to previous methods, as conductive materials with large electrical anisotropy are readily available, whereas further increasing the spin-Hall angle of heavy-metal materials would be challenging. Our findings offer exciting possibilities for directly utilizing these photoexcited high-density currents across metallic interfaces for ultrafast electronics and terahertz spectroscopy.

利用Nd:YAG激光器研究了DKDP晶体元件在激光辐照下的表面损伤特性，对比研究了355 nm和1064 nm激光辐照下晶体元件的表面损伤形貌，分析了每种损伤形貌对应的前驱体和损伤机制。研究结果表明：相对于体损伤，晶体的表面损伤更加复杂，在脉宽约10 ns、损伤概率小于等于50%的激光能量密度辐照下，DKDP晶体的表面损伤主要有带坑底空腔损伤坑、表面损伤裂纹、平底损伤坑、表面烧蚀四种典型形貌。通过光学显微镜和扫描电子显微镜的成像和分析发现：带坑底空腔损伤坑和表面损伤裂纹的前驱体都是晶体体缺陷，平底损伤坑的前驱体则可能是表面加工裂纹、裂纹内碎屑、表层体缺陷等中的一种或多种，表面烧蚀主要由表面污染和浅表层缺陷形成。与熔石英光学元件一样，表面损伤仍然是晶体元件抗激光辐照损伤的薄弱环节。

Dynamically controlling terahertz (THz) waves with an ultracompact device is highly desired, but previously realized tunable devices are bulky in size and/or exhibit limited light-tuning functionalities. Here, we experimentally demonstrate dynamic modulation on THz waves with a dielectric metasurface in mode-selective or mode-unselective manners through pumping the system at different optical wavelengths. Quasi-normal-mode theory reveals that the physics is governed by the spatial overlap between wave functions of resonant modes and regions inside resonators perturbed by pump laser excitation at different wavelengths. We further design/fabricate a dielectric metasurface and experimentally demonstrate that it can dynamically control the polarization state of incident THz waves, dictated by the strength and wavelength of the pumping light. We finally numerically demonstrate pump wavelength-controlled optical information encryption based on a carefully designed dielectric metasurface. Our studies reveal that pump light wavelength can be a new external knob to dynamically control THz waves, which may inspire many tunable metadevices with diversified functionalities.

Metasurfaces have exhibited great capabilities to control electromagnetic waves, and many multifunctional metasurfaces were recently proposed. However, although angle-multiplexed meta-devices were successfully realized in reflection geometries, their transmission-mode counterparts are difficult to achieve due to the additional requirements. Here, we design and fabricate a transmissive angle-multiplexed meta-polarizer in the microwave regime based on a multilayer metasurface. Coupled-mode-theory analyses reveal that the device exhibits distinct angle-dependent transmissive responses under excitations with different polarizations, and such differences are further enhanced by multiple scatterings inside the device. Microwave experimental results are in good agreement with numerical simulations and theoretical analyses.