Terahertz Electro-Optics in Semiconductor Nanostructures

本研究的重点是一类新型半导体光电器件的制造和研究。这些装置将使研究由强周期场驱动的多体系统的量子动力学成为可能。它们还构成了利用光纤全部400太比特/秒通信带宽的新方法的基石。该装置将使用天线将频率为f（THz）的太赫兹场耦合到一个包含半导体量子阱或超晶格的小区域。频率为f（NIR）的近红外（NIR）辐射靠近半导体带隙，将探测有源区的响应。将监测频率f（边带）= f（近红外）+/- nf（太赫兹）的吸收和边带发射，其中n=整数。人们期望在高太赫兹场中，带间吸收共振和边带强度会发生大的变化，它们会随着太赫兹场强而振荡。在掺杂量子阱中，当太赫兹辐射与地面和第一激发子带之间的跃迁发生共振时，有望产生有效的边带发射。在较高的太赫兹强度下，预测了像倍周期分岔到混沌这样的非线性现象。这项研究为研究生和本科生提供半导体物理、器件制造和光学方面的广泛培训，为他们未来在政府、工业或学术界的职业生涯做好准备。当今突出的技术问题之一是数字信息的快速传播。互联网的线程是光纤，每根光纤都有以每秒40万亿比特的速率传输信息的潜力。现有的技术只能利用1%的带宽，在几十个光频率上同时发送每秒10千兆比特的信息。这项研究的重点是制造和测试一种新型非线性光学器件，它能够选择性地将一个光频率上的信息转移到几太赫兹之外的另一个光频率上。所提出的装置也有望表现出各种令人惊讶的现象，这些现象将检验我们对远离平衡的量子力学系统的理解。这项研究为研究生和本科生提供半导体物理、器件制造和光学方面的广泛培训，为他们未来在政府、工业或学术科学领域的职业生涯做好准备

This research focuses on the fabrication and investigation of a novel class of semiconductor electro-optical devices. These devices will enable the study of quantum dynamics of many-body systems driven by strong periodic fields. They also form a cornerstone of a novel approach to utilizing the full 400 Terabit/s communications bandwidth of optical fibers. The devices will use antennas to couple THz fields with frequency f(THz) into a small region containing semiconductor quantum wells or superlattices. Near-Infrared (NIR) radiation with frequency f(NIR), near the semiconductor band-gap, will probe the response of the active region. Absorption, and the emission of sidebands at frequencies f(sideband) = f(NIR) +/- nf(THz), where n=integer, will be monitored. One expects at high THz fields large shifts in interband absorption resonances, and sideband intensities, which oscillate with THz field strength. In doped quantum wells, efficient sideband emission is expected when THz radiation is resonant with the transition between the ground and first excited sub-bands. At higher THz intensities, nonlinear phenomena like period-doubling bifurcations to chaos have been predicted. This research offers graduate and undergraduate students broad training in semiconductor physics, device fabrication, and optics, which will prepare them for future careers in government, industry, or academe.%%%One of today's outstanding technological problems is the rapid communication of digital information. The threads of the Internet are optical fibers, each of which has the potential to carry information at the rate of 40 trillion bits per second. Existing technology is capable of using only 1% of this bandwidth, by sending 10 gigabits per second on several dozen optical frequencies simultaneously. This research focuses on fabricating and testing a new class of nonlinear optical devices, which are capable of selectively shifting information carried on one optical frequency to another one several Terahertz away. The proposed devices are also expected to exhibit a variety of surprising phenomena, which test our understanding of quantum-mechanical systems driven very far from equilibrium. This research offers graduate and undergraduate students broad training in semiconductor physics, device fabrication, and optics, which will prepare them for future careers in government, industry, or academic science.***