Fundamentals and Applications of Ultra-Slow Light Propagation in Room Temperature Solids

[00:355206 . 06]最近的研究导致了一种技术的发展，这种技术可以使光以大大降低（或增加）的群速度在材料系统中传播。对慢光的兴趣源于概念问题和它在诸如可控延迟线、信息存储设备和量子信息处理等应用中的潜在用途。迄今为止，大多数制造慢光的技术都很难实现，例如涉及到玻色-爱因斯坦凝聚体、热原子蒸汽或低温控制晶体。PI最近展示了一种生产慢光的技术（PRL 90,113903,2003），这种技术更容易实现，因为它需要使用室温固体。它是基于一种新的量子相干过程产生的伴随光谱洞的折射率轮廓的修改。这个光谱洞是由相干居群振荡（CPO）产生的，这是两个应用场之间基态居群在拍频处的周期性调制。利用这种技术，他用红宝石晶体演示了低至57米/秒的光速。相干居群振荡也为研究光学材料的结构特性提供了一种极为灵敏的光谱工具。在亚历山大变石中，铬离子可以位于镜像对称或反转对称的两个位置，并且这两个位置表现出不同的饱和行为。PI发现（Science 301200,2003），在某些波长，反转位置占主导地位，亚历山大变石显示出超慢的传播，而在其他波长，镜像位置占主导地位，导致超光速（但因果）传播。提出的研究计划将从几个相关的角度研究室温固体中的慢速和快速光传播。问题包括通过CPO可以延迟或推进多少脉冲的基本限制，以及如何通过使用不同的材料和不同的相互作用几何形状来优化效果。沿着这条路线，一个特别有趣的可能性涉及到掺铒光纤的光延迟研究，这是一个极其重要的系统组成部分。初步实验证明了这种效应的存在。相关的问题包括基于这种效应构建光延迟线和存储设备的效果如何，以及通过慢光和快光技术可以实现哪些其他物理和应用。作为一个例子，我们期望在这样的条件下会有一个非常强的声光相互作用，即光在给定材料中的速度等于声速。拟议活动的更广泛影响包括以下几个方面。PI的研究小组由一大批不同的个人组成，他们被鼓励合作，探索他们研究项目的知识基础。所提议的工作的主题领域是公众感兴趣的，而且PI在这个主题上的早期工作已经被大众媒体所报道。在这个项目期间，将举行几次关于提案主题领域的讲习班。

0355206BoydRecent research has led to the development of techniques that can allow light to propagate through a material system with a greatly reduced (or increased) group velocity. Interest in slow light results both from conceptual issues and for its potential usefulness in applications such as controllable delay lines, information storage devices, and quantum information processing. Most techniques to date for the production of slow light have been very difficult to implement, involving for instance a Bose-Einstein condensate, hot atomic vapors, or cryogenically controlled crystals.The PI has recently demonstrated (PRL 90,113903,2003)a technique for the production of slow light that is much easier to implement in that it entails the use of room-temperature solids. It is based on the modification of the refractive index profile that accompanies the spectral hole created by a novel quantum coherence process. This spectral hole is created as the result of coherent population oscillations (CPO), the periodic modulation of the ground state population at the beat frequency between two applied fields. Using this technique, he demonstrated light velocities as low as 57 m/s using a ruby crystal. Coherent population oscillations can also provide an extremely sensitive spectroscopic tool for studying the structural properties of optical materials. In the case of alexandrite, chromium ions can be located at either sites with mirror or inversion symmetry, and these two sites show different sorts of saturation behavior. The PI has found (Science 301,200,2003)that at certain wavelengths the inversion sites dominate and alexandrite shows ultra-slow propagation, whereas at other wavelengths the mirror sites dominates leading to superluminal (but causal) propagation.The proposed research program will study slow and fast light propagation in room temperature solids from several related points of view. Questions include the fundamental limitations to how much a pulse can be retarded or advanced by means of CPO and how to optimize the effect through the use of different materials and different interaction geometries. A particularly interesting possibility along these lines involves studies of optical delay in erbium doped optical fibers, an extremely important system component. Preliminary experiments have shown the existence of this effect. Related questions include how well can one build optical delay lines and storage devices based on this effect, and what other physics and applications are enabled by slow-and fast-light techniques. As an example, it is expected that there will be a very strong acoustooptic interaction under conditions such that the velocity of light in a given material becomes equal to the velocity of sound.The broader impact of the proposed activity includes the following aspects. The PI 's research group consists of a large diverse group of individuals who are encouraged to work collaboratively and to explore the intellectual underpinnings of their research projects. The subject area of the proposed effort is one that is of interest to the general public, and indeed the PI's earlier work on this topic has been covered by the popular press. Several workshops on the subject area of the proposal will be held during the course of this project.