Atom-Light Interaction in High-Pressure Optical Waveguides

本计画的目的是研究非线性光学与集体光子量子效应，其中光被限制在充满原子气体的光学空芯波导中。几百巴的缓冲气体压力导致系统的宽的压力加宽的带宽，通常尖锐的原子物理谱线和固态物理system.In以前的工作中，我们已经证明了原子光谱的铷池填充500巴的氩气和氦气缓冲气体，分别。在紧密聚焦的光束几何形状中的压力和饱和加宽导致数十纳米的光谱带宽。量子光学系统的室温线宽在能量单位上接近热能，我们观察到强耦合缀饰态（耦合原子-光本征态）系统的热平衡证据。虽然我们的相互作用长度目前受到驱动光束的高斯焦点的空间深度的限制，但我们期望通过波导中的适当光限制可以达到光学密集的制度，从而允许新颖的高带宽非线性光学系统和集体光子量子效应。利用波恩重点研究单位现有的专业知识，我们计划调查空芯光子晶体光纤和金属波导。后者是发达的中红外光谱区，但在光学制度的金属波导的等离子体激元诱导效应的制造和探索是一个活跃的研究领域。显然，一个相当大的进一步增加的相互作用长度是可能的充气空芯光子晶体光纤，这将是随后的研究内program.We预计将展示宽带频率混合，利用可能的指数抑制的压力加宽波导系统中的吸收。共振泵浦样品中增加的相互作用长度允许有趣的热平衡光子量子效应，如热态和凝聚有序极化激元态之间的极化激元（即耦合混合原子-光准粒子）的玻色-爱因斯坦相变。这种密集填充的光波导的一个有趣的观点，在通常的气相和固态条件之间插入，在于探索新的方法来定制光的状态。

The aim of this project is the study of nonlinear optics and collective photonic quantum effects with light confined in optical hollow core waveguides filled with an atomic gas. A buffer gas pressure of several hundreds of bars leads to a wide pressure-broadened bandwidth of the system, interpolating between the usual sharp atomic physics spectral lines and the band structure of solid state physics systems.In previous works, we have demonstrated atomic spectroscopy on a rubidium cell filled with 500 bar of argon and helium buffer gas, respectively. Pressure and saturation broadening in a tightly focused optical beam geometry leads to a spectral bandwidth of tens of nanometers. The room temperature linewidth of the well controlled quantum optical system in energy units approaches the thermal energy, and we have observed evidence for thermal equilibrium of the strongly coupled dressed state (coupled atom-light Eigenstate) system. While our interaction length is presently limited by the spatial depth of the Gaussian focus of the driving light beam, we expect that with appropriate light confinement in a waveguide the optically dense regime can be reached, allowing for novel, high bandwidth nonlinear optical systems and collective photonic quantum effects. Taking advantage of the existing expertise of the Bonn focused Research Unit, we plan to investigate both hollow core photonic crystal fibers and metallic waveguides. The latter ones are well-developed for the mid-infrared spectral region, but the fabrication and the exploration of plasmon-induced effects of metal waveguides in the optical regime are an active field of research. Clearly, a considerable further increase of the interaction length is possible with gas-filled hollow core photonic crystal fibres, which will be studied subsequently within the program.We expect to demonstrate wideband frequency mixing, taking advantage of the possible exponential suppression of absorption in the pressure broadened waveguide system. The increased interaction length in a resonantly pumped sample allows for intriguing thermal equilibrium photonic quantum effects, as a Bose-Einstein-like phase transition of polaritons (i.e. coupled hybrid atom-light quasiparticles) between a thermal state and a condensed, ordered polariton state. An intriguing perspective of such densely filled optical waveguides, interpolating between usual gas phase and solid state conditions, lies in the exploration of novel ways to tailor the state of light.