Speckle Evolution and Modes in Random Media

随机介质中的散斑演化和模式

• 批准号: 0907285
• 负责人: Azriel Genack
• 金额: $ 37万
• 依托单位: CUNY Queens College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-06-01 至 2013-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0907285&HistoricalAwards=false
• 关键词: Speckle; Evolution; Modes; Random; Media

****NON-TECHNICAL ABSTRACT****We explore and control our environment and stay in touch with one another via waves such as light, sound, quantum mechanical electron waves, and microwave radiation. Such waves flow freely through empty space or ordered structures but are impeded by scattering in the pervasive disorder of the world around us. Waves transmitted through disordered samples fluctuate wildly in space due to the scattering. They produce a unique random speckle pattern of intensity, which is a unique fingerprint of the random sample. Nevertheless, there are common elements in the transport for any kind of wave. Microwave and optical measurements demonstrate that each statistical property of transport can be characterized by a single parameter and all such parameters are simply related. The value of these parameters reflects the changing spatial extent of the wave in a transition between freely diffusing and localized waves trapped by disorder within the sample. This award supports a project that will use microwave and optical measurements to obtain the speckle pattern of radiation for different frequencies. The patterns will be analyzed to find the underlying modes of oscillation of the wave, which are akin to the fundamental vibrations of a violin string, as well as the allowed channels for transmission through opaque samples. Approaching the study of wave propagation from different perspectives will lead to a more complete understanding of wave propagation with applications to telecommunications, nano-electronics, photonics and imaging. In addition the microwave and optical measurements will be carried out by high school students, undergraduates and graduate students, and by a postdoctoral fellow. Thus, this project will provide a stimulating training ground for young researchers. ****TECHNICAL ABSTRACT****The nature of wave propagation in disordered samples reflects the spatial and spectral variation of the modes within the medium. When modes are spectrally isolated, the intensity inside the sample is exponentially peaked. However, modes that overlap spectrally may extend throughout the sample. But the wave in the interior of a random sample is hidden from view. This award supports a project that will attempt to overcome this limitation by using microwave and optical measurements of the transformation of transmitted speckle patterns with frequency shift to reveal both the underlying electromagnetic modes and the transmission channels of random systems in the transition from localized to diffusive transport. Analysis of the speckle patterns will enable the calculation of all transmission properties of the waves through the random media. If successful, problems such as the dynamics of localized waves or the statistics of speckle evolution, which have eluded a full theoretical analysis because they involve occasionally overlapping modes, will be resolved. The eigenchannels of the transmission matrix and associated transmission coefficients will be found. This will give an alternate description of the localization transition and will facilitate strategies that will allow for strong transmission of properly phased light though opaque samples. This work will strengthen the CUNY Photonic Center established to enhance the technological base of the New York metropolitan area. Students from local high schools and undergraduates, as well as graduate students and more senior researchers will be actively engaged in the laboratory. Their careers will be fostered by research, which combines microwave and optical techniques to probe a diverse set of problems of fundamental and applied interest.

* 非技术摘要 * 我们探索和控制我们的环境，并通过光，声音，量子力学电子波和微波辐射等波与彼此保持联系。这样的波可以在空旷的空间或有序的结构中自由流动，但在我们周围普遍混乱的世界中，它会受到散射的阻碍。通过无序样品传播的波由于散射而在空间中剧烈波动。 它们产生独特的强度随机散斑图案，这是随机样品的独特指纹。 然而，在任何种类的波的传输中有共同的元素。 微波和光学测量表明，每一个统计性质的运输可以用一个单一的参数，所有这些参数是简单的相关。这些参数的值反映了在自由扩散和被样品内的无序捕获的局部化波之间的过渡中的波的变化的空间范围。 该奖项支持一个项目，该项目将使用微波和光学测量来获得不同频率的辐射散斑图案。 将分析这些模式，以找到波的基本振荡模式，这类似于小提琴弦的基本振动，以及允许通过不透明样品传输的通道。 从不同的角度来研究波的传播，将导致一个更完整的理解波的传播与电信，纳米电子学，光子学和成像的应用。 此外，微波和光学测量将由高中生、本科生和研究生以及一名博士后进行。 因此，该项目将为年轻研究人员提供一个激励性的培训场所。* 技术摘要 * 无序样品中波传播的性质反映了介质中模式的空间和光谱变化。 当模式被光谱隔离时，样品内的强度呈指数峰值。 然而，在光谱上重叠的模式可以贯穿样品延伸。但是随机样本内部的波是隐藏的。 该奖项支持一个项目，该项目将试图克服这一限制，通过使用微波和光学测量传输的散斑图案与频移的转换，以揭示潜在的电磁模式和随机系统的传输通道，从本地化到扩散运输的过渡。 散斑图的分析将使得能够计算波通过随机介质的所有传输特性。如果成功的话，诸如局域波的动力学或散斑演化的统计等问题将得到解决，这些问题由于偶尔涉及重叠模式而无法进行全面的理论分析。 将找到传输矩阵的本征通道和相关的传输系数，这将给出局部化转变的另一种描述，并将有助于实现适当相位的光通过不透明样品的强传输的策略。这项工作将加强为加强纽约大都市区的技术基础而建立的纽约市立大学光子中心。来自当地高中和本科生的学生，以及研究生和更高级的研究人员将积极参与实验室。他们的职业生涯将通过研究来培养，研究结合了微波和光学技术，以探索各种基础和应用问题。