All-Optical Switching and Strong Coupling Using Tunable Whispering-Gallery-Mode Resonators

全光开关是光子学的长期目标。光对光的操纵通常可以通过物质的非线性光学响应来实现。这种非线性光-物质相互作用的影响可以通过光学谐振器放大。模体积V越小，谐振器的Q因子越高，放大率越高。虽然存在许多提供高Q / V值的谐振器概念，但光进出高Q谐振器的耦合通常效率低下。对于高g窃窃私语走廊模式谐振器，情况有所不同，其中锥形光纤耦合允许耦合效率超过99%。我们建议使用在本研究单元第一个资助期间开发的可调谐低语走廊模式谐振器用于这种全光开关应用。实验一方面应利用表面吸附分子与谐振模的倏逝场相互作用的“体”非线性响应来进行。另一方面，我们试图开展实验，利用所谓的“强耦合状态”中的单原子的非线性响应。这种方法的动机是在单光子水平上实现非线性相互作用的观点。如果这种光子-光子相互作用能够在强耦合状态下实现，这将为量子通信和量子信息处理框架中的重要应用开辟道路。

All-optical switching is a long-standing goal of photonics. The manipulation of light with light is in general possible via the nonlinear optical response of matter. The effect of this nonlinear light-matter interaction can be amplified be means of optical resonators. This amplification becomes higher the smaller the mode volume V and the higher the Q factor of the resonator are. While a number of resonator concepts exist that offer high values of Q / V, coupling of light into and out of high Q resonators is often inefficient. The situation is different for high-g whispering-gallery-mode resonators, where tapered fiber coupling allows coupling efficiencies exceeding 99 %. We propose the use of the tunable whispering-gallerymode resonators that have been developed during the first funding period of this Research Unit for such all-optical switching applications. The experiments shall on the one hand be carried out using the "bulk" nonlinear response of surface-ads orbed molecules that interact with the evanescent field of the resonator modes. On the other hand, we seek to carry out experiments that exploit the nonlinear response of single atoms in the so-called "strong coupling regime". This approach is motivated by the perspective of realizing a nonlinear interaction at the level of single photons. If such a photon-photon interaction could be realized in the strong coupling regime, this would open the route towards important applications in the framework of quantum communication and quantum information processing.