Towards Quantum Organic Optoelectronics

点击翻译按钮获取中文摘要

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.