Probing polariton condensation dynamics by multiquantum coherent spectroscopy in organic optical microcavities

塑料激光器的前景令人兴奋，因为它们可以简单地从溶液中加工，大大降低了制造成本，而且塑料的灵活性为构思柔性激光器提供了机会。此外，每个组件的光学性质可以综合调节；这些材料可以设计成在可见光光谱的红、绿或蓝区域非常有效地发光。然而，实现商业上可行的塑料激光器面临许多挑战，主要是因为这些材料的激发态在接近发射波长的波长处强烈吸收光，因此高激发态密度是诱导激光效应所必需的。然而，已经提出了一种很有前途的替代方法，并使用传统的半导体，即所谓的极化激光进行了演示。这些设备利用了光和电子的强烈相互作用，在其中产生了新的准粒子，可以被认为是部分光子和部分电子。这些准粒子被称为极化子，它们具有非常特殊的性质，即所谓的玻色子。实际上，这意味着两个或更多的极化子可能占据相同的量子力学状态。如果玻色子密度足够高，其中很大一部分玻色子占据了最低的量子态，在这一点上，量子效应(相干；就像一大群合作的滑冰运动员组合，当聚光灯照射到他们身上时，都在精细的编排中表演)在宏观尺度上自发地显现出来，即极化子波函数在大的长度尺度上在空间上重叠。极化子的强光子特性使得这种相干性达到了对激子(激发电子)具有挑战性的程度，激子(激发电子)是“肮脏的”玻色子，在高密度下经历相互湮灭。在偏振子激光器中，自发相干是激光产生的根源：脱离自发相干态的光泄漏是激光的光源。在这个项目中，我们将开发一个实验装置，它将以前所未有的详细程度探测引起自发相干的极化子之间的相互作用。

The prospect of 'plastic' lasers, in which each component is composed of polymers or molecules, is exciting because these can be processed simply from solution, reducing significantly their cost of fabrication, and because the flexibility of plastics presents opportunities to conceive flexible lasers. Furthermore, the optical properties of each component can be tuned synthetically; these materials can be designed to emit light very efficiently in the red, green or blue regions of the visible spectrum. However, implementing commercially viable plastic lasers presents many challenges, primarily because excited states of these materials absorb light strongly at wavelengths close to the emission wavelength, and thus high excited-state densities are necessary to induce laser effects. However, a promising alternative approach has been proposed and demonstrated using traditional semiconductors, so-called polariton lasers. These devices exploit the strong interaction of light and electrons, in which new quasi-particles that can be considered to be part photons and part electrons, are generated. These quasi-particles are termed polaritons, and they have the very special property that are so-called bosons. Practically, this means that two or more polaritons may occupy the same quantum-mechanical state. If the boson density is high enough, a large fraction of these occupy the lowest quantum state, at which point quantum effects (coherence; like a large ensemble of cooperative skater pairs all performing in exquisite choreography when the spotlight is upon them) become apparent spontaneously on a macroscopic scale, i.e., the polariton wavefunctions overlap spatially over large lengthscales. The strong photonic character of polaritons permits such coherence to an extent that is challenging for excitons (excited electrons), which are 'dirty' bosons and undergo mutual annihilation at high density. Spontaneous coherence is at the origin lasing in polariton lasers: the optical leakage of out of the spontaneously coherence state is the source of laser light. In this project, we will develop an experimental apparatus that will probe with unprecedented detail the interactions between polaritons that give rise to spontaneous coherence.