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Theoretical studies of coupled quantum well excitons and microcavity dipolaritons, their transport dynamics and applications in optical devices

耦合量子阱激子和微腔偶极子的理论研究、输运动力学及其在光学器件中的应用

基本信息

批准号：
EP/L022990/1
负责人：
Joe Wilkes
金额：
$ 30.32万
依托单位：
CARDIFF UNIVERSITY
依托单位国家：
英国
项目类别：
Fellowship
财政年份：
2014
资助国家：
英国
起止时间：
2014 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FL022990%2F1
关键词：
Theoretical studies coupled quantum well

项目摘要

In the last 100 years, the advent of quantum mechanics has spawned rapid technological advances and renewed growth in our understanding of the world around us. A few decades ago, quantum wells - layers of material just tens of atoms thick - made possible the study of a new two-dimensional (2D) world where quantum effects are exceptionally prominent.The proposed work entails the study of particles known as excitons trapped inside quantum wells. An exciton is comprised of a negatively charged electron and a positively charged hole that are bound by the attractive forces between them. Laser light excites an electron so that it freely roams the 2D quantum well plane. This leaves an empty space - a hole - that the electron can eventually re-occupy. The hole also traverses the quantum well and can be treated as a real particle with mass and charge. A fascinating variety, known as indirect excitons, is the main focus. These are where electrons and holes are separated into closely spaced wells so that excitons acquire a dipole orientation. In particular, their 2D transport and ways to control their motion are studied.Excitons are short lived and decay to emit light. In their brief existence, they display a dramatic variety of physical phenomena. One such phenomenon is the macroscopically ordered exciton state. In this state, excitons spontaneously organise themselves into clusters, equally spaced and uniform in size. The exact cause of this has been heavily debated since its discovery more than a decade ago. An explanation of this effect in terms of the intricate interplay of forces between charges will be sought.Excitons also give rise to particles known as polaritons. Light can be absorbed to make an exciton which later decays to emit light. However, that light gets reabsorbed to make another exciton. The perpetual cycle continues at such a rapid pace that we no longer think in terms of an exciton and light but rather a new mixed state called a polariton. When quantum wells are placed between two mirrors to trap the light, microcavity polaritons are realised. These have their own unique properties and are neither like excitons or light. They display striking features such as Bose-Einstein condensation - an exotic state of matter predicted by Bose and Einstein almost a century ago. Excitons and polaritons provide a means to study the beauty of quantum mechanics in a whole new way and are among the best tools to craft the outer limits of human understanding. In this work, a new breed of polariton will be studied where the polariton's exciton part is a dipolar indirect exciton. The motion of these dipolaritons can be controlled both electrically and optically. They enable new types of experiment and new ways to manipulate light.The ultimate goal of the work is to employ the remarkable nature of excitons and polaritons in the development of new optical technology. Devices such as optical transistors have the potential to revolutionise the communication era. Currently, optical fibres transfer information at high speed using light whilst information processing is done using electronic transistors. The conversion between optical and electronic signals leads to bottlenecks in communication networks. Optical transistors will solve this problem and will become an integral part of future communication systems. The goal is to identify new ways to create optical transistors mediated by excitons and polaritons. The success of this work will contribute to a globally emerging industry.

在过去的100年里，量子力学的出现催生了快速的技术进步，并使我们对周围世界的理解重新增长。几十年前，量子阱——只有几十个原子厚度的材料层——使得研究一个新的二维（2D）世界成为可能，在这个世界里，量子效应非常突出。这项提议的工作需要研究量子阱中被称为激子的粒子。激子由一个带负电的电子和一个带正电的空穴组成，它们之间受引力的束缚。激光激发一个电子，使其在二维量子阱平面上自由漫游。这就留下了一个空穴，电子最终可以重新占据这个空穴。这个空穴也穿过量子阱，可以看作是一个有质量和电荷的真实粒子。一个迷人的品种，被称为间接激子，是主要的焦点。在这些地方，电子和空穴被分隔成紧密间隔的阱，这样激子就获得了偶极子的方向。特别研究了它们的二维传输和运动控制方法。激子寿命很短，衰变后会发光。在它们短暂的存在中，它们表现出各种各样的物理现象。其中一种现象就是宏观有序的激子态。在这种状态下，激子自发地组织成簇，间隔相等，大小均匀。自十多年前发现这一现象以来，其确切原因一直备受争议。将从电荷间力的复杂相互作用方面寻求对这种效应的解释。激子也会产生被称为极化子的粒子。光可以被吸收而产生激子，激子随后衰减而发光。然而，光被重新吸收，产生另一个激子。这个永恒的循环以如此快的速度继续着，以至于我们不再用激子和光的方式来思考，而是用一种叫做极化子的新混合状态来思考。当量子阱被放置在两个镜子之间以捕获光时，微腔极化就实现了。它们有自己独特的性质，既不像激子也不像光。它们表现出惊人的特征，比如玻色-爱因斯坦凝聚——一种由玻色和爱因斯坦在近一个世纪前预言的奇特物质状态。激子和极化子提供了一种以全新的方式研究量子力学之美的方法，也是制造人类理解外部极限的最佳工具之一。本研究将研究一种新的极化子，其中极化子的激子部分为偶极间接激子。这些偶极子的运动可以用电学和光学两种方法来控制。它们使新型实验和操纵光的新方法成为可能。这项工作的最终目标是利用激子和极化子的显著性质来开发新的光学技术。光学晶体管等器件有可能彻底改变通信时代。目前，光纤利用光以高速传输信息，而信息处理则利用电子晶体管完成。光电信号的转换是通信网络的瓶颈。光晶体管将解决这一问题，并将成为未来通信系统的重要组成部分。目标是找到新的方法来制造由激子和极化子介导的光学晶体管。这项工作的成功将有助于全球新兴产业的发展。