Quantum properties of polariton condensates in microcavity devices

半导体微腔（MC）是由高反射率的反射镜组成的法布里-珀罗谐振腔，其有源区含有嵌入式量子威尔斯阱。它们使激子和光子限制在一个方向上。强激子-光子耦合在这些结构中的结果形成一类新的玻色子准粒子，描述在二维极化激元或混合激子光子状态。微腔极化激元具有良好的特性，用于研究凝聚现象和许多新的体效应，如固态系统中的超流性，这可以在比激子和原子所需的温度高得多的温度下实现，因为它们的有效质量非常小。MC结构的另一个优点是可以通过外部激光场在微米尺度上精确操纵极化激元状态。此外，强极化激元-极化激元相互作用使得能够产生光子的非经典态。此外，极化激元态的内部结构可以通过适当的MC结构设计容易地修改，从而产生零维或一维限制。我的建议的主要目标将是准确地准备宏观占据高密度极化激元状态与精确的相位信息和控制其偏振和统计特性。为了证明与原子凝聚体的类比，但在固态系统中，我的建议的一个重要部分是致力于研究两个相互作用的极化激元凝聚体的空间和时间相干性。特别设计的零维光子结构也将允许控制影响相干性的量子波动。利用极化激元基态的共振激发，可以有效地产生光子的非经典态，即具有偏振选择性控制的压缩光。极化激元态将通过外部施加的单轴应变和施加的磁场来控制，以实现极化激元的期望自旋性质，从而实现极化激元凝聚体的极化。拟议的研究还将集中在高密度极化激元相位和声学声子之间的相互作用的研究，这将是重要的理解新的现象所产生的凝聚在周期性的电位引起的表面声波。最后，研究了宽带微腔中极化激元凝聚体的压缩效应和相干特性。该研究有望为未来微腔结构在量子信息技术中的应用以及新型光源、混频器和可调谐光学滤波器的开发奠定坚实的基础。

Semiconductor microcavities (MC) are Fabry-Perot resonators which consist of high reflectivity mirrors and which contain embedded quantum wells in the active region. They enable both exciton and photon confinement in one direction. Strong exciton-photon coupling in these structures results in the formation of a new class of bosonic quasiparticles, described in terms of two-dimensional polaritons or mixed exciton photon states. Microcavity polaritons have favourable characteristics for the study of condensation phenomena and novel many body effects such as superfluidity in a solid-state system, which can be achieved at much higher temperature than that required for excitons and atoms due to their very small effective mass. An additional advantage of MC structures is that precise manipulation of the polariton states can be performed on a micrometer scale by an external laser field. In addition, strong polariton-polariton interactions enable the generation of non-classical states of photons. Also the internal structure of polariton states can be easily modified by the appropriate design of MC structures with resultant zero- or one- dimensional confinement. The key aim of my proposal will be accurately prepared macroscopically occupied high density polariton states with precise phase information and control of their polarisation and statistical properties. In order to prove the analogy with atomic condensates, but in a solid state system, one of the important parts of my proposal is dedicated to the study of spatial and temporal coherence of two interacting polariton condensates. Specially designed zero-dimensional photonic structures will also permit control of quantum fluctuations, which affect the coherence. Efficient generation of non-classical states of photons, squeezed light with polarisation selective control will be achieved using resonant excitation of the polariton ground states. Polaritonic states will be controlled by external applied uniaxial strain and applied magnetic field to achieve desired spin properties of polaritons and hence the polarisation of the polariton condensate. The proposed research will also focus on the study of interactions between the high density polariton phase and acoustic phonons, which will be important to understand new phenomena arising from condensation in the periodic potential induced by surface acoustic waves. Finally, the effects of squeezing and coherence properties of the polariton condensate will be investigated in wide band microcavities. The research is expected to lay a strong foundation for the future use of microcavity structures in quantum information technology and for the development of novel light sources, mixers and tunable optical filters.