All Optical, Tunable THz Magnonic Devices

频谱的太赫兹部分是高频光学(红外)技术和微波领域之间具有挑战性的边界区域。太赫兹频谱在一系列应用和行业中提供了许多潜在的优势，包括通信和信息技术、生物成像和健康科学、化学传感和其他安全应用，甚至星载天文学。该项目将研究一种名为亚铁磁体的材料的基本性质，并以新颖的方式使用这些材料来开发一种用于超高速通信和信息处理应用的新型太赫兹源。该项目将研究薄膜中的亚铁磁体在不同温度和极高磁场下的特性。此外，亚铁磁体的独特性质将被用于一种新型的磁性设备，该设备通过使用极短的光脉冲来激发亚铁磁体的磁性运动，从而获得前所未有的速度。科学地了解这些材料的基本性质及其在设备中的实现对于支持不断发展的21世纪数字经济的下一代磁性设备和超高速信息技术至关重要。这项研究将支持两名来自代表不足的物理学群体的研究生，将展示多达六名本科生的高级研究，并将有助于促进与少数民族服务学院研究生项目的合作。实现实用太赫兹(THz)电子学的一种有前途的方法依赖于自旋电子学，它通过操纵电子自旋来扩展和放大传统电子学的特性。所提出的新的器件结构将显著地缩小自旋电子太赫兹源的带宽，同时还提供了较宽的载波频率可调性。该器件的核心是一个磁性三层系统，由一个偏振器层、一个非磁性自旋传输层和一个发射层组成，它们都生长在光学透明的衬底上。太赫兹载频由发射极层中的自旋波模式决定，而自旋波的频率由磁性特性(饱和磁化强度、g因子、自旋波硬度等)决定。发射器的位置。亚铁磁性材料能够在很大程度上控制发射体的磁性，并因此能够控制太赫兹发射的频率。我们将用飞秒时间分辨磁光克尔效应[tr-MOKE]研究这些原型全光器件的太赫兹尺度动力学，用铁磁共振[FMR]研究较慢的自旋动力学。此外，将使用元素特定的光谱技术(X射线探测的FMR[X-FMR]和飞秒尺度的高次谐波产生[HHG])详细研究亚铁磁性动力学。这项研究将解决三个基本问题：(1)详细了解赋予铁磁体独特性质的相互竞争的交换作用；(2)利用这些性质来改进自旋电子太赫兹发射器；以及(3)使用极端磁场修改太赫兹尺度的磁响应。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The terahertz portion of the spectrum is the challenging boundary region between higher frequency optical (infra-red) technology and the microwave realm. The terahertz spectrum offers many potential advantages across a range of applications and industries, including communications and information technology, biological imaging and health sciences, chemical sensing and other security applications, and even spaceborne astronomy. This project will examine the fundamental properties of a class of materials called ferrimagnets and use those materials in novel ways to develop a new kind of terahertz source for very high speed communications and information processing applications. This project will examine the properties of ferrimagnets in thin films, at different temperatures and at very high magnetic fields. Furthermore, the unique qualities of ferrimagnets will be used in a novel magnetic device that achieves unprecedented speed by using extremely short pulses of light to excite motion of the magnetic properties of the ferrimagnet. The scientific understanding of the fundamental properties of these materials and their implementation in devices is crucial for the next generation of magnetic devices and ultra-high speed information technology that supports the evolving 21st century digital economy. The research will support two graduate students from under-represented groups in Physics, will expose up to six undergraduates in advanced research, and will help foster collaboration with the graduate program of a Minority Serving Institution.One promising approach to realize practical terahertz (THz) electronics relies on spintronics, which extends and amplifies the properties of conventional electronics via the manipulation of electron spin. The proposed novel device architecture will significantly narrow the bandwidth of spintronic THz sources of while also providing for wide tunability of the carrier frequency. The core of the proposed device is a magnetic tri-layer system consisting of a Polarizer layer, a non-magnetic spin transport layer, and an Emitter layer, all grown on optically transparent substrates. The THz carrier frequency is governed by spin wave modes in the Emitter layer and the frequency of the spin waves is determined by magnetic properties (saturation magnetization, g-factor, spin wave stiffness, etc.) of the Emitter. Ferrimagnetic materials enable a very large degree of control of magnetic properties of the Emitter and hence in the frequency of the THz emission. The THz scale dynamics of these prototype all-optical devices will be studied with fs time-resolved magneto-optic Kerr effect [tr-MOKE] and slower spin dynamics will be investigated with ferromagnetic resonance [FMR]. Moreover, the ferrimagnetic dynamics will be examined in detail using element-specific spectroscopic techniques (x-ray detected FMR [X-FMR] and fs-scale high harmonic generation [HHG]). The research will address three fundamental issues: (1) Understanding in detail the competing exchange interactions that give ferrimagnets their unique properties; (2) Harnessing these properties for the improvement of spintronic THz emitters; and (3) Modifying the THz-scale magnetic response using extreme magnetic fields.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.