Enhancing Light-Matter Interfaces via Collective Self-Organization

本量子非线性光学研究项目的主要目标是研究一种新型的光-物质界面，该界面由激光驱动冷原子实现，具有非常大的耦合强度，低吸收和长原子相干时间。它是由于波长尺度结构中原子的西西弗斯冷却和原子聚束的同时作用而产生的。光-物质相互作用自产生的场对原子在单次通过介质时的质心运动有很大影响，在没有空腔的情况下产生自组装的空间结构。这些结构反作用于场，产生长相干时间、慢光和由绝对不稳定（相变）产生的量子光学模式。研究人员正在利用这种光-物质界面：1)当激光驱动气体被放置在干涉仪中时，观察到低光电平（可能是单光子）非线性相移；2)测量由相变附近的原子驱动气体散射的辐射的量子统计特性，以检验最近对相关迪克模型的预测；3)测量被驱动气体中自发模式的形成，并与原子空间重组相关；4)用反传播贝塞尔光束抽吸气体时观察到三维（3D）西西弗斯冷却，从而显著增加相互作用的量子相干时间；5)建立光物质相互作用的自洽模型，该模型考虑了光场的传播、原子的偏振、质心原子运动和西西弗斯三维冷却；6)扩展自由空间类迪克模型，以解释在该系统中发现的新物理现象。这项工作将为一个独特的物理系统提供新的实验和理论理解，该系统在量子非线性光学中具有应用，特别是在单光子非线性相互作用的发展以及在良好控制环境中研究经典和量子相变方面。该计划还对远离平衡态的量子相变、冷原子物理和凝聚态物理的研究产生了影响。更广泛的影响：从广泛的角度来看，该计划有可能通过增加非线性光学灵敏度来改善非线性光学器件的性能，从而使器件尺寸缩小并降低功率要求成为可能。从教育的角度来看，该项目将培养两名研究生，在光学物理领域的实验和理论技术的跨学科环境中。值得注意的是，该项目在指导妇女和少数民族科学家方面非常有效，并在当地小学和中学开展了大量的外联活动，以帮助吸引更多的人学习科学学科。

The primary goal of this quantum nonlinear optics research program is to study a new type of light-matter interface, realized by laser driving cold atoms, that has very large coupling strength, low absorption, and long atomic coherence times. It arises due to the simultaneous action of Sisyphus cooling of the atoms and atomic bunching in wavelength-scale structures. Fields self-generated by the light-matter interaction have a large affect on the center-of-mass motion of the atoms in a single pass through the medium, giving rise to self-assembled spatial structures in the absence of a cavity. These structures act back on the fields, giving rise to long coherence times, slow light, and quantum optical patterns arising from an absolute instability (phase transition). The investigators are using this light-matter interface to: 1) Observe a low-light-level (potentially single-photon) nonlinear phase shift when the laser-driven gas is placed in an interferometer; 2) Measure the quantum statistical properties of the radiation scattered by the driven gas of atoms near the phase transition to test recent predictions of an associated Dicke-like model; 3) Measure spontaneous pattern formation in the driven gas and correlate to the atomic spatial reorganization; 4) Observe three-dimensional (3D) Sisyphus cooling when pumping the gas with counterpropagating Bessel beams, thereby dramatically increasing the quantum coherence time of the interaction; 5) Develop a self-consistent model of the light matter interaction that accounts for propagation of the optical fields, polarization of the atoms, center-of-mass atomic motion, and Sisyphus cooling in 3D; and 6) Extend the free-space Dicke-like model to account for the new physics found in this system. This work will provide new experimental and theoretical understanding of a unique physical system that has applications to quantum nonlinear optics, especially in the development of single-photon nonlinear interactions and the study of classical and quantum phase transitions in a well-controlled environment. The program has also has implications for the study of far-from equilibrium quantum phase transitions, cold-atom physics, and condensed matter physics. Broader Impact: From a broad perspective, the program has the potential to improve the performance of nonlinear optical devices by increasing the nonlinear optical sensitivity making it possible to shrink the size of the device and lower the power requirements. From an educational perspective, the program will results in the training of two graduate students in an interdisciplinary environment in both experimental and theoretical techniques in the enabling field of optical physics. It is noteworthy that the PI has been very effective in mentoring women and minority scientists and has undertaken substantial outreach in the local area elementary and middle schools to help attract more people to the science disciplines.