Topological effects in optically anisotropic microcavities

该项目的目的是拓扑有趣的微腔（MC）的实验实现和理论理解，以及受保护的光子态和光子和激子极化激元的定向传输的证明。这里提出的这些示例性系统的理论研究，预计将形成一个新的概念，用于描述光学模式和它们的偏振系统的低对称性的基础。此外，拓扑光子系统是非常有趣的基础科学，以及在应用方面，可以预期提供一个里程碑，实现器件的片上光学数据传输和处理。激子-极化激元在室温及更高温度下建立玻色-爱因斯坦凝聚体的能力进一步显示了这种拓扑系统在量子计算中应用的潜力。作为一个普遍的新概念，我们将利用光学双轴系统中的特殊模式特性，其中对称性破缺由谐振器结构和所涉及材料的光学各向异性的组合引起。由光学各向异性、光学线性、互易性和非手性腔材料制成的普通MC应通过实验产生、研究和理论理解。非平凡性应通过腔光子和激子-极化激元的性质（复模色散、偏振或更确切地说是伪自旋）来证明。使用横向结构，类狄拉克点的简并性将被提升，以诱导拓扑保护的边缘模式，并使光子或激子-极化激元的相应传输成为可能。在这方面，粒子的极化状态或者更确切地说是伪自旋被期望是拓扑保护的，并且因此可以用于实验证明。所提出的概念不需要外场、复杂的超材料或本身拓扑非平凡的电子系统，因此非常有前途的实际应用。根据我们的初步研究，广泛研究和众所周知的光学单轴半导体ZnO和GaN是非常适合作为各自的腔材料。因此，它们的光轴的取向不必平行于MC的限制方向对准。首先，我们将实现和研究裸光子MC，所使用的材料的透明度光谱范围。成功后，我们将把我们的研究扩展到强激子-光子耦合（激子-极化激元）的领域。

Aim of the project is the experimental realisation and theoretical understanding of topological interesting microcavities (MC), as well as the proof of protected photonic states and directed transport of photons and exciton-polaritons. The theoretical investigations of these exemplary systems here proposed are expected to form a basis for a generally new concept for the description of optical modes and their polarization in systems of low symmetry. Further, topological photonic systems are highly interesting for fundamental science as well as, regarding applications, can be expected to provide a milestone towards the realization of devices for on-chip optical data transport and processing. The capability of exciton-polaritons to build up a Bose-Einstein condensate at room temperature and above show further the potential of such topologic systems for application in quantum computing.As a general new concept, we will utilize special mode properties in optically biaxial systems, in which symmetry breaking is induced by the combination of the resonator structure and the optical anisotropy of the involved materials.Topologically non-trivial MC made out of optically anisotropic, otherwise optically linear, reciprocal and non-chiral cavity materials shall be experimentally produced, investigated and theoretically understood. The non-triviality shall be proven by means of properties (complex mode dispersion, polarization or rather pseudo-spin) of the cavity photons and exciton-polaritons. Using lateral structuring, the degeneracy of Dirac-like points shall be lifted for inducing of topological protected edge-modes and to enable corresponding transport of photons or exciton-polaritons. In this regard, the polarization state or rather the pseudo-spin of the particles is expected to be topological protected and thus can be used for experimental proof. The proposed concept does not need external fields, complicated meta-materials or per se topological non-trivial electronic systems and thus is very promising for practical applications.As based on our preliminary studies, the widely investigated and well known optically uniaxial semiconductors ZnO and GaN are very suitable as respective cavity materials. The orientation of their optical axis thereby must not be aligned parallel to the direction of the confinement of the MC. First, we will realise and investigate bare photonic MC, for the transparency spectral range of the used materials. At success, we will extend our investigations to the regime of the strong exciton-photon coupling (exciton-polaritons).