Development of novel schemes of cavity-enhanced Raman spectroscopy for the sensitive detection of gas-phase species in the environment

开发腔增强拉曼光谱的新方案，用于环境中气相物质的灵敏检测

• 批准号: NE/I000844/1
• 负责人: Michael Hippler
• 金额: $ 14.3万
• 依托单位: University of Sheffield
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FI000844%2F1
• 关键词: Development; novel; schemes; cavity; enhanced

Spectroscopy is at the heart of environmental sciences. Spectroscopic techniques are indispensable in analytical applications to identify and quantify species which are relevant for the environment. Raman spectroscopy is an important technique in this context since it can analyse substances which are difficult to detect with other methods. In the condensed phase, Raman spectroscopy has become a major analytical technique. Applications of Raman spectroscopy for trace gas analysis, however, has not found wide-spread use so far due to the inherent weakness of Raman transitions. In this proposal, an alternative approach to sensitive Raman spectroscopy is suggested, cavity-enhanced Raman spectroscopy with diode lasers. In this proposal, a diode laser as Raman pump source is amplified in an optical cavity. This increase in laser power will make spontaneous Raman signals much stronger compared to a standard Raman experiment. To increase sensitivity even further, a special cavity with specific mirrors will be used which also amplifies the Raman signals themselves (stimulated Raman, passively amplified). In a final experiment, the possibility to selectively amplify the transitions of a target species by seeding the cavity with the corresponding light will be explored (stimulated Raman, actively amplified). It is expected that cavity enhancement will increase Raman signals by orders of magnitude; spontaneous Raman signals are linearly proportional to the laser pump power, and in a good optical cavity, power build up by a factor of 10000 can easily be achieved. In addition, stimulated Raman schemes have orders of magnitude higher sensitivity than spontaneous Raman schemes. Both power build up in an optical cavity and stimulated Raman excitation will result in a much greater sensitivity than conventional Raman techniques. The expected increased sensitivities of the proposed Raman schemes will be required for the trace gas detection and monitoring of pollutants in the environment. These schemes would allow new and improved analytical measurements with a portable instrument suitable for real time, in situ field measurements of pollutants in the environment with an instrument that can measure all components of air simultaneously with great selectivity and sensitivity with a large dynamic range for mixing ratios. In addition, these new instruments have the potential to enable further new applications relevant to environmental sciences, including trace detection of molecular hydrogen, and isotope-selective measurements of nitrogen and oxygen and isotope tracer experiments. This proposal to develop new and innovative technologies for Raman spectroscopy has the potential to lead to the emergence of Raman spectroscopy as a major analytical tool in the gas phase, comparable to the important role Raman spectroscopy currently has for chemical analysis of liquids and solids.

光谱学是环境科学的核心。光谱技术在分析应用中是不可缺少的，可以识别和量化与环境有关的物种。拉曼光谱在这方面是一项重要的技术，因为它可以分析用其他方法难以检测到的物质。在凝聚态中，拉曼光谱已成为一种主要的分析技术。然而，由于拉曼跃迁固有的弱点，拉曼光谱在痕量气体分析中的应用迄今尚未得到广泛应用。本文提出了一种灵敏拉曼光谱的替代方法，即二极管激光器的腔增强拉曼光谱。在这个方案中，二极管激光器作为拉曼泵浦源在光学腔中被放大。激光功率的增加将使自发拉曼信号比标准拉曼实验强得多。为了进一步提高灵敏度，将使用一个带有特定反射镜的特殊腔，该腔也可以放大拉曼信号本身（受激拉曼，被动放大）。在最后的实验中，将探索通过向腔中注入相应的光来选择性地放大目标物种跃迁的可能性（受激拉曼，主动放大）。预计腔增强将使拉曼信号增加几个数量级；自发拉曼信号与激光泵浦功率成线性比例，在良好的光腔中，功率可以很容易地增加到10000倍。此外，受激拉曼格式的灵敏度比自发拉曼格式高几个数量级。光腔中的功率积累和受激拉曼激发都将导致比传统拉曼技术更高的灵敏度。在环境中痕量气体的探测和污染物的监测方面，将需要拟议的拉曼计划预期的灵敏度提高。这些方案将允许使用一种便携式仪器进行新的和改进的分析测量，该仪器适用于环境中污染物的实时现场测量，该仪器可以同时测量空气的所有成分，具有很高的选择性和灵敏度，具有较大的混合比动态范围。此外，这些新仪器有可能使与环境科学有关的进一步新应用成为可能，包括分子氢的痕量探测、氮和氧的同位素选择性测量以及同位素示踪剂实验。这一发展拉曼光谱新技术和创新技术的建议有可能导致拉曼光谱作为气相的主要分析工具出现，与拉曼光谱目前在液体和固体化学分析中的重要作用相当。

项目成果

Cavity-Enhanced Raman Spectroscopy in the Biosciences: In Situ, Multicomponent, and Isotope Selective Gas Measurements To Study Hydrogen Production and Consumption by Escherichia coli.

• DOI: 10.1021/acs.analchem.6b04924
• 发表时间: 2017-01
• 期刊: Analytical chemistry
• 影响因子: 7.4
• 作者: Thomas W Smith;M. Hippler