基于超快自旋-电荷转换的太赫兹辐射源

Terahertz emitters based on ultrafast spin-to-charge conversion

太赫兹技术在成像、传感和安全等方面展现出了巨大的应用潜力和价值.传统的固态宽带太赫兹源主要依赖于非线性光学晶体和光电导天线,而下一代太赫兹技术的一个主要挑战是开发高效、超宽带和低成本的太赫兹源.最近几年,基于自旋电子学的金属磁性异质结太赫兹源获得了很大关注.本文首先将对该类太赫兹源涉及的物理机理进行讨论,主要包括超快退磁和自旋-电荷转换.然后对该类源的效率提升做了探讨,具体的优化方向体现在三个方面:薄膜材料选择(含生长过程控制)、薄膜厚度和薄膜结构设计.文章最后给出简单总结和该领域的展望.

Terahertz technology shows great potential applications in imaging,sensing and security.As is well known,the conventional solid-state broadband terahertz sources rely primarily on the nonlinear optical crystals and photoconductive antennas.Therefore,one major challenge for the next generation of terahertz technology is to develop the high-efficient,ultra-broadband and low-cost terahertz sources.In recent years,much attention has been paid to the spintronic terahertz emitters made of the metallic magnetic heterostructures on a nanometer scale.In this paper,the underlying physical mechanisms associated with this type of terahertz emitter is discussed.They mainly include the ultrafast demagnetization and the spin-charge interconversion processes.In order to further improve the terahertz emission efficiency,three main aspects are considered:appropriate choice of the materials(including conditions of the sample growing),film thickness,and new structure design.In the end,a short conclusion and future perspective for this research direction are given briefly.