Facilitating remote chemical sensing with random Raman lasing

摘要非技术描述：本提案的驱动动机是化学特定遥感（僵局检测）和深部组织光学成像的需求日益增长。从地面粉末的远程评估到光学生物医学成像，都需要评估混浊介质中材料的化学成分。振动光谱学已被证明在复杂介质中识别化学物质是成功的。然而，信号的强度通常被认为是一个主要的限制。提出的研究计划旨在利用最近发现的受激拉曼辐射在无序介质中的效应来克服这些主要缺点。它可以将信号增加到106-109的惊人值，使距离目标数公里远的粉末的简单而无缝的远程化学传感成为可能。该计划将对环境科学、生物医学科学和医学诊断成像以及国土安全产生深远影响。本文提出的器件新颖的工作原理和技术方法将应用于器件的设计和构造中，将对许多需要光散射效应的研究和应用领域产生积极影响。利用受激拉曼散射增强随机散射组织的生物医学成像设备的一个即将到来的应用，可以通过提供对深层组织化学成分的简单访问，潜在地影响超过10亿人的生活。从教育的角度来看，该项目将为直接参与研究的学生提供无与伦比的培训和专业发展机会，显著提升他们未来的职业前景。特别是，该计划将使学生接触多学科研究的“完整周期”，从计算模拟到样品制备和表征，从观测现象的初步分析描述到后续迭代仪器优化，从基本思想到现实生活中的实际应用。从外联的角度来看，该计划提出了几个针对学龄学生和他们的老师的重点。德克萨斯农工大学位于美国发展最快、以西班牙裔人口为主的地区的中心，一些活动将专门针对不同的学生群体。技术描述：该计划建立在计算科学、工程、光学科学和化学的最新进展基础上，通过散射介质引入遥感和生物医学成像的变革方法。该计划建立在这些初步结果的基础上，其主要研究目标是基本理解随机介质中有效非线性光学相互作用的机制和局限性。为了实现这一目标，我们将：(1)从根本上了解随机介质中受激拉曼散射的机制、条件和局限性。我们将使用开发的计算和实验工具来研究介质的吸收和散射参数，不均匀性和夹杂物的影响，以及广泛的激发参数，如波长，脉冲持续时间和光束形状，对随机介质中受激拉曼散射的阈值和效率的影响。(2)探索利用时空形状激光脉冲控制随机拉曼激光的可能性。在许多实际情况下，随机介质不会随时间发生明显变化。这为优化入射辐射的波前以增强介质内部的非线性相互作用创造了机会。(3)利用已发展的随机拉曼激光概念进行遥感和深部组织生物成像。我们将利用Aims 1-2的结果设计一个实用的远程化学传感和深部组织生物成像系统。

Title: FACILITATING REMOTE SENSING VIA RANDOM RAMAN LASINGABSTRACTNontechnical Description: The driving motivation for this proposal is the growing necessity for chemically specific remote sensing (standoff detection) and deep tissue optical imaging. From remote assessment of powders on the ground to optical biomedical imaging, there is a need to evaluate the chemical composition of materials a turbid medium. Vibrational spectroscopy has proven to be successful in identifying chemicals in complex medium. However, the strength of the signal is often considered as a major limitation. The proposed research program aims at overcoming those major disadvantages by utilizing a recently discovered effect of stimulated Raman emission in disordered medium. It allows increasing the signal by an astonishing value of 106-109 making it possible simple and seamless remote chemical sensing of powders km's away from the target. The proposed program will have a profound effect on environmental science, biomedical science and medical diagnostic imaging, and homeland security. The novel operating principle of the proposed device and technology and methods, which will be used in the device design and construction, will positively affect a number of research and application areas where light scattering effects are important. Just a single impending application of biomedical imaging device utilizing stimulated Raman scattering enhancement in randomly scattering tissues can potentially affect the lives of more than a billion people by providing a simple access to the chemical composition of deep-laying tissues. From the educational standpoint, proposed program will provide unmatched opportunities for training and professional development of the students directly involved in the research, significantly advancing their future career prospects. In particular, the program will expose the students to the "full cycle" of multidisciplinary research, from computational simulations to sample preparation and characterization, from initial formulation of analytical description of the observed phenomena to the follow-up iterative instrument optimization, from a fundamental idea to a real-life practical application. From the outreach perspective, the program presents several thrusts aimed at school-aged students and their teachers. Texas A&M University is located in the middle of the fastest growing, predominantly Hispanic-populated region in the US, and several activities will be specifically targeting the diverse student population.Technical Description: The proposed program builds up on the recent advances in computational science, engineering, optical sciences and chemistry to introduce a transformative approach for remote sensing and biomedical imaging through scattering medium. The proposed program is built on those preliminary results and has a major research objective of fundamental understanding the mechanisms and limitations of efficient nonlinear optical interactions in random media. To accomplish this goal, we will: (1)Fundamentally understand the mechanism, conditions and limitations of stimulated Raman scattering in random media. We will use both the developed computational and experimental tools to investigate the effects of absorption and scattering parameters of the media, the effects of inhomogeneities and inclusions, as well as a broad range of excitation parameters, such as wavelength, pulse duration and beam shape, on the threshold and efficiency of stimulated Raman scattering in random media.(2)Explore the possibility of controlling random Raman lasing using temporally and spatially shaped laser pulses. In many practical situations, random media does not vary appreciably over time. It creates an opportunity to optimize the wavefront of the incident radiation to enhance the nonlinear interaction inside the medium.(3)Utilize the developed concept of random Raman lasing for remote sensing and deep tissue biological imaging. We will use the results of Aims 1-2 to design a practical system for remote chemical sensing and deep tissue biological imaging.