Exciton Polaritons in Microcavities
Exciton Polaritons in Microcavities
复制标题
微腔中的激子极化子
DOI：
10.1007/978-3-642-24186-4_5
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
Krizhanovskii D
中科院分区：
文献类型：
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作者：
Krizhanovskii D
在这一章中，我们研究宏观占据凝聚体，这可以观察到在半导体微腔条件下的共振或非共振激发。在共振激发下，由于光参量振荡（OPO）的作用，极化激元凝聚形成强非平衡态。在非共振非相干泵浦系统的情况下，较高能量的极化激元的分布显示出一些热化，但由于有限的极化激元寿命，所得到的极化激元凝聚也远离热力学平衡。在本章中，我们证明了这两个系统具有非常相似的性质。我们揭示了极化激元-极化激元相互作用和非平衡性质对凝聚体性质的影响。由于极化激元系统的非平衡特性，在阈值以上可以观察到不同能量和k矢量的多个极化激元能级的凝聚。触发凝聚的特定k矢量由局部无序势景观决定。我们还通过测量一阶（g（1））和二阶（g（2））相关函数研究了单凝聚模的相干性。我们发现这些函数的衰减时间为150 ps，比1. 5 ps的极化激元寿命长得多。尽管极化激元凝聚体是一个非平衡系统，但衰变的强烈减慢允许观察到平衡的、相互作用的BEC的相干衰变过程。实验上观察到的相互作用的特征是g（1）函数的高斯形式，并且随着凝聚体中粒子数量的增加，相干时间饱和。虽然预测，这些影响还没有观察到原子玻色-爱因斯坦凝聚体。
In this chapter, we study macroscopically occupied condensates, which can be observed in semiconductor microcavities under conditions of resonant or non-resonant excitation. In the case of resonant excitation, polariton condensates form due to optical parametric oscillation (OPO) and are strongly non-equilibrium states. In case of non-resonantly incoherently pumped system, the distribution of the higher energy polaritons shows some thermalisation, but the resultant polariton condensates are also far from thermodynamic equilibrium due to finite polariton lifetime. In this chapter, we show that both systems have very similar properties. We reveal the effects of polariton–polariton interactions and non-equilibrium character on the condensate properties. Above threshold condensation into several polariton levels with different energies and k-vectors is observed, which arises from the non-equilibrium character of the polariton system. The specific k-vectors at which condensation is triggered are determined by the local disorder potential landscape. We also investigate the coherence of a single condensed mode by measuring the first (g(1))- and second (g(2))-order correlation functions. We find that the decay times of these functions are $$\sim 100\mbox{ \textendash }150\,\mathrm{ps}$$ , much longer than the 1.5 ps polariton lifetime. Even though the polariton condensate is a non-equilibrium system, the strong slowing down of the decay allows coherence decay processes characteristic of an equilibrium, interacting BEC to be observed. The signature of the interactions is a Gaussian form for theg(1)-function and a saturation of coherence time with increasing number of particles in the condensate, as observed experimentally and confirmed theoretically. Although predicted, these effects have not been observed for atom BECs.