Next Generation Raman: Developing A Monolithic Spatial Heterodyne Spectrometer For Multi-Scale Chemical Mapping In Marine Environments

该项目的目标是开发一种全新的仪器--单片式拉曼光谱仪，旨在产生海洋环境中所有深度的固体、液体和/或气体的化学图像。该仪器使用一种名为拉曼光谱的技术，将样品在成分特定波长(颜色)上散射的光收集到二维(2D)图像(图片)中，以生成采样区域的化学地图。该项目的关键技术进展是新型拉曼仪器，称为单片式空间外差拉曼光谱仪(MSHRS)。尽管在支持海洋应用拉曼光谱所需的仪器平台和采样系统的开发方面取得了很大进展，但拉曼光谱仪技术的进步并没有跟上在这些环境中使用的步伐。拉曼测量的价值，再加上部署现有仪器的努力和成本，证明开发一种适用于深海等极端环境的新型拉曼光谱仪是合理的。该项目正在开发的MSHRS克服了现有海洋操作系统的一些主要限制，如仪器尺寸和重量、功率要求、坚固性(没有移动部件)和灵敏度。正在开发的MSHRS技术将允许部署必要的仪器平台和采样系统，以支持广泛的海洋应用的拉曼光谱。这将支持对矿物、不透明固体和水中重要化学物种(如甲烷、二氧化碳(CO2)、硫酸盐和硫化物)的拉曼测量，环境深度可达3.6公里，那里的压力是地表的360倍。MSHRS将生成化学地图，以显示这些和其他化学物质的一维和二维空间分布，即使在自然环境中典型的复杂混合物中也是如此。拉曼测量的价值，与部署现有仪器的努力和成本相平衡，证明了这种新型拉曼光谱仪的开发是合理的。与目前在海洋拉曼应用中使用的“现成”光谱仪相比，建议的MSHRS本身就是一个重大进步，缩小了尺寸，同时提高了相对于传统设计的坚固性和灵敏度。而且，当与小型二极管激光器和最新的成像探测器相结合时，该仪器可以真正实现小型化，而不会损失性能。MSHRS可能足够小，可以部署在自动游泳和漂流平台(称为滑翔机，Argo Floats)或遥控飞行器(ROV)上的机械手手臂上。这项工作将支持开发一种新的拉曼能力，这种能力将促进广泛的新应用以及海洋系统中的基本化学测量，并将推动变革性的海洋学研究。虽然拟议工作的重点是研究海洋应用的过程动力学，但这项技术的适用性要广泛得多。除了对基础和应用研究的支持外，使用在线分析和过程评估的新能力的工业应用也是可能的。调查人员有很长的辅导代表不足群体学生的历史，这个项目支持的两名学生是目前的女研究生。这些学生还将受益于与劳伦斯·利弗莫尔国家实验室的科学家合作，并将获得国家实验室对国土安全和国防应用的看法。最近由Angels Group(项目首席研究员，PI)描述的空间外差拉曼光谱仪(SHRS)是一种完全不同的设计，与传统的色散拉曼系统相比具有巨大的优势，包括更大的接受角和更大的视场，扩展光源的光吞吐量增加100到10,000，非常高的光谱分辨率和更宽的光谱范围。SHRS的设计还允许光谱仪非常小，因为光谱分辨率不是设备大小的强烈函数。在拟议的工作中，我们将通过开发单片式SHRS(MSHRS)将SHRS提升到一个新的水平，其中光谱仪的光学部件是一片熔融的二氧化硅。这将提供一个坚固的拉曼光谱仪，对冲击和振动免疫，在尺寸和重量上比目前的海洋拉曼仪器小一个数量级时具有更高的灵敏度。MSHRS将根据分辨率、光谱范围、吞吐量和对振动的稳健性进行评估。拉曼系统品质因数(如分辨率、灵敏度、光吞吐量等)将使用固体、液体、溶液和气体来确定。在模型应用中，我们将评估MSHRS在监测具有一系列海洋环境特征的模型氧/缺氧混合系统中的反应动力学。作为MSHRS稳定性和精确度的衡量标准，我们还将评估其在测量与基本海洋相关的物种的选定同位素比率方面的用途。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The goal of this project is to develop a radically new type of instrument, a monolithic Raman spectrometer, designed to generate chemical images of solids liquids and/or gases in ocean environments at all depths. The instrument uses a technique called Raman Spectroscopy, where light scattered off of a sample at composition specific wavelengths (colors) is collected in a 2-dimensional (2D) image (picture) to produce a chemical map of the sampling area. In this project the key technological advancement is the new type of Raman instrument, called a Monolithic Spatial Heterodyne Raman Spectrometer (MSHRS). Although great progress has been made in the development of instrument platforms and sampling systems necessary to support Raman spectroscopy for oceanographic applications, advances in Raman spectrometer technology have not kept pace for use in these environments. The value of Raman measurements, balanced by the effort and cost of deploying current instruments, justifies the development of a new type of Raman spectrometer that is suitable for extreme environments like the deep ocean. The MSHRS being developed in this project overcomes some major limitations with existing systems for operation in the oceans such as instrument size and weight, power requirement, ruggedness (no moving parts), and sensitivity. The MSHRS technology being developed will allow deployment of instrument platforms and sampling systems necessary to support Raman spectroscopy for a broad range of oceanographic applications. This will support Raman measurements on minerals, opaque solids, and in water for important chemical species such as methane, carbon dioxide (CO2), sulfate, and sulfides in environments to depths up to 3.6 km, where the pressure is 360 times higher than at the surface. The MSHRS will generate chemical maps to show the 1D and 2D spatial distribution of these and other chemicals, even in complex mixtures typical of natural environments. The value of Raman measurements, balanced by the effort and cost of deploying current instruments, justifies the development of this new type of Raman spectrometer. The proposed MSHRS alone will be a major advance over "off the shelf" spectrometers currently used in marine Raman applications, reducing the size while increasing robustness and sensitivity over conventional designs. And, when combined with small diode lasers and the latest imaging detectors, the instrument can be truly miniaturized with no loss of performance. The MSHRS is potentially small enough to be deployed on autonomous swimming and drifting platforms (called gliders, Argo floats) or manipulator arms on remotely operated vehicles (ROVs). This work will support the development of a new Raman capability that will facilitate a wide range of new applications as well as basic chemical measurements in marine systems and will fuel transformative oceanographic research. While the focus of the proposed work is the study of process dynamics for oceanographic applications; the technology has much wider applicability. In addition to support of basic and applied research, industrial applications using the new capability for on-line analysis and process evaluation are likely. The investigators have a long history of mentoring students from underrepresented groups and the two students supported by this project are current female graduate students. These students will also benefit by collaborating with scientists at Lawrence Livermore National Laboratory and will gain a National Lab perspective on homeland security and defense applications. The Spatial Heterodyne Raman Spectrometer (SHRS), recently described by Angels group (the project principal investigator, PI), is a radically different design, offering tremendous advantages over conventional dispersive Raman systems, including 10 to 100 times larger acceptance angle and subsequently a much larger field of view, 100 to 10,000 higher light throughput for extended sources, very high spectral resolution and a wide spectral range. The SHRS design also allows for the spectrometer to be extremely small because the spectral resolution is not a strong function of device size. In the proposed work we will take the SHRS to the next level by developing a Monolithic SHRS (MSHRS) where the spectrometer optical components are a single piece of fused silica. This will provide a robust Raman spectrometer, immune to shock and vibrations, with increased sensitivity at a size and weight orders of magnitude smaller than current oceanographic Raman instruments. The MSHRS will be evaluated in terms of resolution, spectral range, throughput and robustness to vibration. Raman system figures of merit (e.g., resolution, sensitivity, light throughput, etc.) will be determined using solid, liquid, solutions and gases. In model applications we will evaluate the MSHRS for monitoring reaction dynamics in model oxic/anoxic mixing systems characteristic of a range of oceanographic environments. As a measure of the stability and precision of the MSHRS we will also evaluate its use for measuring selected isotope ratios for species relevant to the fundamental ocean.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.