Terahertz Electron Hole Recollisions

太赫兹电子空穴碰撞

• 批准号: 1405964
• 负责人: Mark Sherwin
• 金额: $ 56.5万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1405964&HistoricalAwards=false
• 关键词: Terahertz; Electron; Hole; Recollisions

Non-technical abstract:In high-energy physics, the structure of matter is explored by accelerating and colliding elementary particles like electrons and protons. In condensed matter physics, the fundamental excitations are called quasi-particles. The most familiar quasi-particles are electrons and holes in semiconductors, which can be created for example in a solar photovoltaic cell - by light with a sufficiently short wavelength. In this project, electrons and holes will be created by a weak near-infrared laser with a wavelength slightly longer than is visible to the human eye, and will be made to accelerate and then recollide with one another by a very strong electric field oscillating nearly 1 trillion times per second (1 Terahertz). The recollision process will be studied by analyzing the spectrum (which wavelengths are present) in the transmitted near-infrared light. This spectrum has been shown to contain up to 18 separate nearinfrared wavelengths, or sidebands, in addition to the wavelength of the near-infrared laser that creates electron-hole pairs. This research will elucidate how much quasiparticles can be accelerated without being disturbed by defects or the motion of atoms in their host material. The proposed research may lead to faster and more energy efficient optical communications and internet, and improved optical clocks that are necessary in the global positioning system. This project will support the training of two Ph. D. students, who will learn a variety of skills that are critical to preserving U. S. competitiveness in the high-technology sector.Technical abstract:High-order sideband generation, a new phenomenon in the interaction of light with matter, was recently discovered in the PI's research group. A relatively weak, continuous-wave near-infrared (NIR) laser at frequency ~350 THz, and an intense laser at frequency ~0.5 THz are incident on a thin film of semiconductor. A comb of equally-spaced sidebands is emitted, with sharp lines at sideband frequency = NIR frequency + 2n THz frequency, where n is an integer. Combs with up to 14 sidebands (order up to 2*14=28) above NIR frequency have been observed. The high-order sidebands can be understood in terms of a semiclassical model similar to one that was first introduced to explain high-order harmonic generation, an analogous phenomenon that occurs for atoms in intense laser fields. In high-order-sideband generation (HSG), the NIR laser creates excitons, bound electron-hole pairs. The strong THz field ionizes the excitons, and accelerates the resulting electron and hole into a large-amplitude oscillation. When the electron and hole recollide, the excess kinetic energy is carried off in sidebands above the NIR frequency. This project will explore the onset of high-order sideband generation, whether there is a fundamental limit on the number of observable sidebands, whether the shape of the sideband spectrum can be controlled, and whether, in the case of a circularly-polarized terahertz field, the polarization of the near-ir radiation is rotated. By exploring the limits of HSG, the proposed research will elucidate potential applications of HSG to electro-optic technologies ranging from optical communications to optical clocks. This project will support the training of two Ph.D. students, who will learn a variety of skills including near-ir and terahertz optics, cryogenics, electronics, computer programming, and mechanical and optomechanical design.

非技术摘要：在高能物理学中，物质的结构是通过加速和碰撞电子和质子等基本粒子来探索的。在凝聚态物理学中，基本激发称为准粒子。最常见的准粒子是半导体中的电子和空穴，它们可以在太阳能光伏电池中通过波长足够短的光产生。在这个项目中，电子和空穴将由波长稍长于人眼可见光的弱近红外激光产生，并且将被加速，然后通过振荡近红外的非常强的电场相互重新碰撞。每秒 1 万亿次（1 太赫兹）。将通过分析透射近红外光中的光谱（存在哪些波长）来研究重碰撞过程。除了产生电子空穴对的近红外激光的波长之外，该光谱已被证明包含多达 18 个独立的近红外波长或边带。这项研究将阐明在不受缺陷或主体材料中原子运动干扰的情况下，准粒子可以加速多少。拟议的研究可能会带来更快、更节能的光通信和互联网，以及全球定位系统所需的改进的光时钟。该项目将支持培养两名博士生，他们将学习对保持美国在高科技领域的竞争力至关重要的各种技能。技术摘要：高阶边带生成，交互中的新现象PI 的研究小组最近发现了光与物质的关系。频率约为 350 THz 的相对较弱的连续波近红外 (NIR) 激光和频率约为 0.5 THz 的强激光入射到半导体薄膜上。发射等间隔边带梳，边带频率 = NIR 频率 + 2n THz 频率处有锐线，其中 n 是整数。已观察到具有高于 NIR 频率的多达 14 个边带（阶数高达 2*14=28）的梳。高阶边带可以用半经典模型来理解，该模型类似于最初为解释高阶谐波产生而引入的模型，高阶谐波产生是强激光场中原子发生的一种类似现象。在高阶边带生成 (HSG) 中，近红外激光产生激子、束缚电子空穴对。强太赫兹场使激子电离，并将产生的电子和空穴加速成大振幅振荡。当电子和空穴重新碰撞时，多余的动能在近红外频率以上的边带中被带走。该项目将探讨高阶边带生成的开始、可观测边带的数量是否存在根本限制、边带频谱的形状是否可以控制，以及在圆偏振太赫兹场的情况下是否可以控制，近红外辐射的偏振发生旋转。通过探索 HSG 的局限性，拟议的研究将阐明 HSG 在从光通信到光时钟等电光技术中的潜在应用。该项目将支持培养两名博士生。学生将学习各种技能，包括近红外和太赫兹光学、低温学、电子学、计算机编程以及机械和光机械设计。

项目成果

Dynamical Birefringence: Electron-Hole Recollisions as Probes of Berry Curvature

动态双折射：电子空穴碰撞作为浆果曲率的探针

• DOI: 10.1103/physrevx.7.041042
• 发表时间: 2017-11
• 期刊: Physical Review X
• 影响因子: 12.5
• 作者: Banks, Hunter B.;Wu, Qile;Valovcin, Darren C.;Mack, Shawn;Gossard, Arthur C.;Pfeiffer, Loren;Liu, Ren;Sherwin, Mark S.
• 通讯作者: Sherwin, Mark S.

Optical frequency combs from high-order sideband generation

高阶边带生成的光学频率梳

• DOI: 10.1364/oe.26.029807
• 发表时间: 2018-10
• 期刊: Optics Express
• 影响因子: 3.8
• 作者: Valovcin, Darren C.;Banks, Hunter B.;Mack, Shawn;Gossard, Arthur C.;West, Kenneth;Pfeiffer, Loren;Sherwin, Mark S.
• 通讯作者: Sherwin, Mark S.