Manipulation and Control of Coherent States in Exciton-Polariton Systems (MacExP)

半导体中激子和光子的强量子耦合导致这两种成分的相干叠加，或称为激子-极化子的准粒子。从基础研究和应用研究的角度来看，这种混合模式的出现都是有趣的。强的粒子间相互作用是由激子组成的，而极低的有效质量和高迁移率是由光子组成的。激子-极化子凝聚的研究领域是在证明了稀原子气体的真正玻色-爱因斯坦凝聚后不久开辟的，它在量子光学领域开辟了新的篇章。这一关于固体准粒子的重大突破导致了对冷凝相关现象和相变的大量探索，如自发相干积累、超流动性和超导性。甚至基于极化激子拉比振荡的量子比特和在可见光或太赫兹（THz）范围内发射的新型光源，如极化激子激光器和太赫兹玻色子激光器，也被提出使用。近年来，为了研究太赫兹辐射与量子阱微腔系统的相互作用，在实验中进行了一些独立的尝试，将太赫兹辐射与极化子系统结合起来。在这个项目中，将更好地理解太赫兹辐射和极化气体在线性和非线性状态下如何相互作用，这将为超快操纵和控制飞行-物质耦合以及未来涉及极化系统的实用太赫兹产生方案的发展铺平道路。这激发了对包括超快光谱实验和微腔极化子在内的各种配置中太赫兹诱导效应的系统研究，这些研究在本项目中进行了概述。利用数字全息技术直接测量拉比振荡，并研究瞬态太赫兹脉冲对相干态的影响。时间分辨光致发光研究将进一步提供受脉冲太赫兹辐射影响的极化子凝聚体的动力学。因此，瞬态电场对极化子凝聚物的影响将被探讨，这是固体中凝结研究的一个独特的测试平台。在此背景下，将对相干态的操纵和控制以及凝聚态和非凝聚态极化子气体之间或极化态和光子态之间的超快切换进行探讨。因此，该项目将加深我们对太赫兹激子-极化子耦合相关现象的理解，并通过新颖而复杂的实验加强两个学科交叉的发展，最终目标是进一步利用光-物质相互作用来实现新的光学量子技术和光源概念。

Strong quantum coupling of excitons and photons in semiconductors results in coherent superpositions of the two components, or quasiparticles called exciton-polaritons. The appearance of such mixed modes is interesting from both the point of view of fundamental and applied research. Strong interparticle interactions result from the exciton component, while extremely low effective mass and high mobility are due to the photonic component. The field of condensation of exciton-polaritons opened up in the previous decade shortly after the demonstration of true Bose-Einstein condensates of dilute atomic gases, which opened a new chapter in the field of quantum optics. This major breakthrough on quasiparticles in solids led to a vast exploration of condensation-related phenomena and phase transitions, such as spontaneous coherence built-up, superfluidity and superconductivity. Even the use of qubits based on polariton Rabi oscillations and novel light sources emitting in the visible or terahertz (THz) range such as polariton lasers and THz bosonic lasers have been proposed. Within the last few years, a few independent efforts have been made to combine THz radiation and polariton systems in experiments, with the aim to study interaction of THz radiation and quantum-well microcavity systems. In this project, a better understanding of how THz radiation and polaritonic gases interact with each other both in the linear and nonlinear regime will be gained, which will pave the way for ultrafast manipulation and control oflight-matter coupling and the development of future practical THz-generation schemes involving polariton systems. This motivates a systematic investigation of THz-induced effects in various configurations involving ultrafast spectroscopy experiments and microcavity polaritons, which are outlined in this project. Rabi oscillations will be directly measured using a digital holography technique and the effects of transient THz pulses on the coherent state will be investigated. Time-resolved photoluminescence studies will further give access to the dynamics of polariton condensates influenced by the presence of pulsed THz radiation. Thereby, the effects of transient electric fields on condensates of polaritons, which are a unique testbed for condensation studies in solids, will be probed. In this context, light will be shed on the manipulation and control of coherent states and the ultrafast switching between a condensed and uncondensed polariton gas or a polaritonic and photonic regime will be explored. Thus, this project will deepen our understanding of phenomena related to THz-exciton-polariton coupling and enhance development at the crossroads of two disciplines with novel and sophisticated experiments, with the ultimate goal of enabling further utilization of light-matter interaction for novel optical quantum technologies and light-source concepts.