Renormalization and Phase Transitions of Excitons in 2D Nanostructures: Photonics at the University of Pittsburgh

本项目主要研究GaAs和InGaAs耦合量子阱中激子的非线性光学性质。当电场垂直作用于这些阱时，这些结构中的激子中的电子和空穴在空间上分离，从而导致几种非线性效应。一个具体的项目目标是创造激子电路，使激子像自由载流子一样被电场操纵。这包括模拟非均匀电场和应力的影响，并开发增加这些结构中激子迁移率的方法。这项任务涉及与样品制造商的合作。第二个目标是在这种量子阱结构的基础上，研究一种高效的室温光学晶体管。在这个方案中，一束光打开或关闭另一束光。这涉及到理解这些结构中激子的多体重整化效应，这是一个将与几位理论家合作追求的目标。该项目还包括对本科科学教育的实质性承诺。匹兹堡大学在以前的国家科学基金会资助下开始了光子学本科证书课程。目前的项目包括努力扩大该计划，为几名本科生创造从事光子学研究的机会。当光被半导体吸收时，光子粒子可以转变成一种被称为激子的新型能量粒子。激子像光子一样携带光能，但像电子一样在半导体晶体中运动。通过制造被称为双量子阱的特殊层状结构，我们可以使这些激子粒子响应应力和电场而移动。在这个项目中，我们研究双量子阱中激子的性质，目的是为这些光学粒子创建类似于电子电路的电路。这些结构中激子的波长对照射到它们的光的强度也非常敏感。我们希望利用这种效应来开发一种光学晶体管，在这种晶体管中，一束光可以开关另一束光的开关，就像电子晶体管开关电信号的开关一样。这些效应是“光子学”领域的一部分，在“光子学”中，人们制造出利用光子的设备，就像电子学利用电子一样。随着对快速通信的需求不断增长，将技术推向光信号而不是电子信号，该领域是我们经济中一个不断增长的部门。该项目不仅涉及光子学研究，还涉及光子学教育的实质性承诺。匹兹堡大学在以前的国家科学基金会资助下开始了光子学本科证书课程。目前的项目包括扩大该计划的努力。特别的是，这个项目为几个本科生创造了做光子学研究的机会。

This project focuses on the nonlinear optical properties of excitons in GaAs and InGaAs coupled quantum wells. When an electric field is applied normal to the wells, the electrons and holes in excitons in these structures become spatially separated, leading to several nonlinear effects. One specific project goal is to create excitonic circuits by which excitons are manipulated by an electric field just like free carriers. This involves modeling the effects of inhomogeneous electric field and stress and developing ways to increase the mobility of excitons in these structures. This task involves a collaboration with sample fabricators. A second goal is to work toward an efficient, room-temperature optical transistor based on this type of quantum well structure. In this scheme one light beam switches another light beam on and off. This involves understanding the many-body renormalization effects of the excitons in these structures, a goal that will be pursued in collaboration with several theorists. This project also includes a substantial commitment to undergraduate science education. An undergraduate Certificate in Photonics program was begun at the University of Pittsburgh under a previous NSF grant. The present project includes efforts to expand that program by creating opportunities for several undergraduates to do research in photonics.When light is absorbed in a semiconductor, the photon particles can be changed into a new type of energy particle known as an exciton. An exciton carries optical energy like a photon but moves through the semiconductor crystal like an electron. By fabricating special layered structures known as double quantum wells, we can cause these exciton particles to move in response to stress and electric field. In this project we study the properties of excitons in double quantum wells, with the aim of creating circuits for these optical particles similar to electronic circuits. The wavelength of the excitons in these structures can also be very sensitive to the intensity of light that hits them. We hope to use this effect to develop an optical transistor, in which one light beam switches another light beam on and off, just as an electronic transistor switches an electrical signal on and off. These effects are part of the field of "photonics," in which devices are made which use photons just as electronics uses electrons. This field is a growing sector of our economy, as the increased need for fast communications pushes technology to optical rather than electronic signals. This project involves not only research in photonics, but also a substantial commitment to photonics education. An undergraduate Certificate in Photonics program was begun at the University of Pittsburgh under a previous NSF grant. The present project includes efforts to expand that program. In particular, this project creates the opportunity for several undergraduates to do research in photonics.