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.

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.

为了研究我国干旱地区核设施附近代表性生物剂量系数，以蒙古束颈蝗（Splingonotus mongolicus Saussure）为例，基于解剖学和几何学建立简化解剖学模型和基于CT断层扫描、Photoshop软件及Python编程等建立体素模型，并分别计算环境介质中⁹⁰Sr、¹³⁷Cs对蒙古束颈蝗不同组织和器官的内外照射剂量系数。为了验证本次计算结果的可行性，将计算结果与ICRP 108号报告进行了比较。由于ICRP 108号出版物采用整体简化模型，因此本文计算结果采用各个器官剂量系数总体平均值。结果显示：⁹⁰Sr对蒙古束颈蝗简化解剖学模型内外照射剂量系数分别为6.59×10^-4 μGyh^-1/Bqkg^-1、6.74×10^-4 μGyh^-1/Bqkg^-1；¹³⁷Cs对蒙古束颈蝗简化解剖学模型内外照射剂量系数分别为1.34×10^-4 μGyh^-1/Bqkg^-1、4.40×10^-3 μGyh^-1/Bqkg^-1；⁹⁰Sr对蒙古束颈蝗体素模型内外照射剂量系数分别为7.87×10^-4 μGyh^-1/Bqkg^-1、6.74×10^-4 μGyh^-1/Bqkg^-1；¹³⁷Cs对蒙古束颈蝗体素模型内外照射剂量系数分别为1.33×10^-4 μGyh^-1/Bqkg^-1、3.51×10^-3 μGyh^-1/Bqkg^-1；ICRP 108号出版物中提供的⁹⁰Sr对参考昆虫的内外照射剂量系数分别为1.00×10^-2 μGyh^-1/Bqkg^-1、3.90×10^-10 μGyh^-1/Bqkg^-1；ICRP 108号出版物中提供的¹³⁷Cs对参考昆虫的内外照射剂量系数分别为3.20×10^-3 μGyh^-1/Bqkg^-1、2.80×10^-3 μGyh^-1/Bqkg^-1。根据以上数据比较，ICRP 108号报告中提供的内照射剂量系数均比本文建立的剂量学模型计算结果大，外照射剂量系数均小，这可能与生物的体型及采用放射性核素衰变粒子及能量有关。本文采用接近生物体形态的简化解剖学模型及与生物体高度重合的体素模型，更加接近于生物体真实受照情况，精确度高、误差小，证明本次建立的昆虫剂量学模型可行。