Towards Quantum Organic Optoelectronics

有机半导体--类似于塑料或汽车涂料的软合成材料--正迅速进入消费电子产品领域，因为它们的成本低，而且易于在大而灵活的表面上制造。也许最重要的是，它们是设计师设计的材料，仅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由电子和空穴的激子束缚络合物主导--很像迷你氢原子。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，这些效应通常归因于原子气体或超低温度。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子器件，其中新的功能是通过使用和操纵量子行为来实现的。**在微观尺度上，单分子的容易分离使它们能够定位在传统的光电子器件中，以创建高效、明亮的单光子源。这类信源是量子密码术和使用量子计量学的超精密测量的核心。量子密码术是一种用于安全通信的方案。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利用有机发光二极管和发光晶体管结构开发高效的单光子源。例如，利用后者来控制单光子发射的空间位置，人们可以设想在用于实现量子算法的大规模光子集成电路上对单独的波导进行寻址。**在宏观尺度上，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，可以获得量子行为。实现这一点的一种方法是在光学谐振器内，在那里可以使分子与共同的光场发生强烈的相互作用。由此产生的准粒子被称为极化子，其有效质量比电子轻100万倍。用量子力学的术语来说，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子可以建设性地干涉，形成一种叫做玻色-爱因斯坦凝聚体(BEC)的奇异物质状态，这是底层粒子的一个巨大的集体波函数。最近已经实现了用于原子气体和基于无机半导体的极化子的BEC，但在这两种情况下都仅限于低温。本计划的第二个目标是研究有机极化子在室温下的丰富的集体行为。预计会出现令人着迷的现象，如超流，即极化子可以绕过障碍物而不受摩擦的影响，并形成被称为暗孤子的极化子光束。从实用的角度来看，在比传统激光低几个数量级的阈值下，极化子的相干、类激光发射可能会发生。与有机半导体的低成本和多功能性相结合，偏振子激光器在化学和生物传感以及作为高强度照明光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.