RUI: Dimensionality Dependence of Semiconductor Ultrafast Optical Response

在纳米尺度上制造可控结构的能力代表着近几十年来最重要的科学进步之一。这种纳米结构已经在各种光电子设备中使用，并有望随着通信速度的提高而变得越来越重要。这些结构的基本物理原理在于电子的量子限制。然而，这种限制对决定非线性光学响应和弛豫速率的超快电子相互作用的影响尚不清楚。这个项目将使用超快光谱学来确定限制如何影响飞秒时间尺度上的相互作用。它始于一组非常纯的不同宽度的半导体异质结的发展。然后，这些样品将通过几种超快光学技术进行研究，以充分表征限制对超快动力学的影响。这个项目将在威廉姆斯学院进行，这是一所完全是本科生的学院，年轻的学生在研究中发挥积极的核心作用。该项目提供的研究培训将使10名本科生在职业生涯的早期就熟悉研究，特别是尖端的光学和电子技术。通信和计算机速度的提高正在推动技术向越来越小的半导体器件发展。随着这些设备的开发，一个基本的问题是：小型化总是更快，还是小型化不是提高速度的最佳方式？这个项目通过探索电子相互作用随着半导体变得非常小而发生变化的方式来开始回答这个问题。它将通过使用超快激光向纳米级半导体结构注入能量，然后测量这些结构的响应。结果将展示大小如何改变最快的电子相互作用，这种相互作用发生在不到万亿分之一秒的时间内。这项工作具有基础和技术重要性，因为这些相互作用最终允许电子在激发后松弛，从而设定电子和光学设备性能的速度限制。这个项目将在威廉姆斯学院进行，这是一个完全本科的机构，年轻的学生在研究中发挥积极的核心作用。该项目提供的研究培训将使本科生在职业生涯的最早阶段就熟悉研究，特别是尖端的光学和电子技术。

The ability to make well-controlled structures on the nanometer scale represents one of the most important scientific advances of recent decades. Such nanostructures are already in use in a variety of optoelectronic devices, and promise to be of increasing importance as communication speeds increase. The fundamental physics of these structures lies in the quantum confinement of electrons. However, the influence of such confinement on the ultrafast electronic interactions which determine both nonlinear optical response and relaxation rates is unclear. This project will use ultrafast spectroscopy to determine how confinement influences interactions on the femtosecond time scale. It begins with the development of a very pure set of semiconductor heterostructures with varying width. These samples will then be studied via several ultrafast optical techniques to fully characterize the influence of confinement on ultrafast dynamics. This project will take place at Williams College, an entirely undergraduate institution in which young students take active, central roles in research. The research training provided by this project will allow ten undergraduates to become familiar with research, and specifically with cutting edge optical and electronic techniques, at the earliest point in their careers.The drive for increasing speed in communications and computers is pushing technology toward ever smaller semiconductor devices. A fundamental question as these devices are developed is the following: is smaller always faster, or is miniaturization not the best way to increase speed? This project begins to answer the question by exploring the ways in which electron interactions change as semiconductors become extremely small. It will proceed by using an ultra-fast laser to inject energy into nanoscale semiconductor structures, and then to measure how those structures respond. The results will demonstrate the ways size alters the fastest electronic interactions, which take place in less than a trillionth of a second. This work is of both fundamental and technological importance, since these interactions ultimately allow electrons to relax after excitation, and thus set the speed limit for electronic and optical device performance. This project will take place at Williams College, an entirely undergraduate institution in which young students step up to take active, central roles in research. The research training provided by this project will allow tenundergraduates to become familiar with research, and specifically with cutting edge optical and electronic techniques, at the earliest point in their careers.