Towards Quantum Organic Optoelectronics

有机半导体类似塑料或汽车油漆的柔软合成材料由于其成本低且易于在大而灵活的表面上制造，正迅速进入消费电子产品领域。也许最重要的是，它们是经过设计的材料，只受化学家的技能和想象力的限制。与传统的无机半导体不同，有机半导体的室温光学性质主要由电子和空穴的激子结合复合物控制，就像一个微型氢原子。这种激子的稳定性提供了使用有机薄膜观察奇异量子效应的可能性，这些量子效应通常归因于原子气体或超低温。通过利用这些效应，该计划旨在实现一系列基于有机半导体的光电器件，其中通过使用和操纵量子行为实现新的功能。在微观尺度上，单分子可以很容易地被隔离，这使得它们可以被放置在传统的光电器件中，以产生高效、明亮的单光子源。这种光源是量子密码学（一种用于安全通信的方案）和使用量子计量学的超精密测量的核心。它们也被用于量子计算的实现，其中利用量子态的性质，如叠加和纠缠来解决复杂的问题。该计划的第一个目标是开发使用有机发光二极管和发光晶体管架构的高效单光子源。例如，使用后者来控制单光子发射的空间位置，可以设想在用于实现量子算法的大规模光子集成电路上寻址单个波导。在宏观尺度上，量子行为可以通过将几个有机分子耦合在一起，使它们以明确的相位关系振荡来获得。实现这一点的一种方法是在光学谐振器内，可以使分子与共同的光场强烈相互作用。由此产生的准粒子称为极化激元，其有效质量比电子轻一百万倍，在量子力学中，它们具有高度扩展的波函数。如果这些波函数开始重叠，处于最低能量状态的极化激元可以相长干涉，形成一种奇特的物质状态，称为玻色-爱因斯坦凝聚（BEC）--底层粒子的巨大集体波函数。BEC最近已经实现了原子气体和基于无机半导体的极化激元，但在这两种情况下都仅限于低温。该计划的第二个目标是研究室温下有机极化激元的丰富集体行为。人们期待着快速的现象，如超流，其中极化激元可以在障碍物周围流动而不会感受到摩擦的影响，并形成称为暗孤子的极化激元光束。从实际的角度来看，相干的，类似激光的发射从极化激元可以发生在阈值几个数量级低于传统的激光器。结合有机半导体的低成本和多功能性，偏振激元激光器在化学和生物传感以及作为高强度照明源方面具有许多潜在的应用。

Organic semiconductors-soft synthetic materials akin to plastics or car paint-are rapidly finding their way into*consumer electronics due to their low cost and the ease with which they can be fabricated on large and flexible*surfaces. Perhaps most importantly, they are designer materials, limited only by a chemist's skill and imagination.*In contrast to conventional inorganic semiconductors, the room-temperature optical properties of organic semiconductors are dominated by excitons-bound complexes of an electron and hole-much like a mini-hydrogen atom. The stability of this exciton offers the potential of using organic films to observe exotic quantum effects typically ascribed to atomic gasses or ultralow temperatures. By exploiting these effects, this Program aims to realise a family of optoelectronic devices, based on organic semiconductors, where new functionality is achieved via the use and manipulation of quantum behaviour.**On the microscopic scale, the ease with which single-molecules can be isolated allows them to be positioned within conventional optoelectronic devices to create highly efficient, bright sources of single-photons. Such sources are at the heart of quantum cryptography-a scheme used for secure communication-and of ultraprecise measurements using quantum metrology. They are also used in implementations of quantum computing, where properties of quantum states such as superposition and entanglement are exploited to solve complex problems. The first objective of the Program is to develop highly efficient single-photon sources using organic light-emitting diode and light-emitting transistor architectures. Using the latter to control the spatial location of single-photon emission, for example, one can envision addressing individual waveguides on a large-scale photonic integrated circuit used to implement quantum algorithms.**On the macroscopic scale, quantum behaviour can be obtained by coupling several organic molecules together so that they oscillate with a well-defined phase relationship. One way to achieve this is within an optical resonator, where molecules can be made to interact strongly with a common optical field. The resulting quasiparticles, called polaritons, possess an effective mass one million times lighter than that of an electron. In quantum mechanical terms, they possess a highly extended wavefunction. If these wavefunctions begin to overlap, polaritons in their lowest energy state can interfere constructively to form an exotic state of matter called a Bose-Einstein condensate (BEC) - a giant collective wavefunction for the underlying particles. BECs have recently been realised for atomic gasses and for polaritons based on inorganic semiconductors, but in both cases have been limited to low temperatures. The second objective of this Program is to study the rich collective behaviour of organic polaritons at room temperature. Fascinating phenomena are expected, such as superfluidity, where polaritons can flow around obstacles without feeling the effect of friction and the formation of polariton beams called dark solitons. From a practical standpoint, coherent, laser-like emission from polaritons can occur at thresholds several orders of magnitude lower than those of conventional lasers. Combined with the low-cost and versatility of organic semiconductors, polariton lasers have many potential applications in chemical and biological sensing and as high-intensity illumination sources.