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FTIR USING ASYNCHRONOUS FEMTOSECOND OPOS: A NEW PARADIGM FOR HIGH-RESOLUTION FREE-SPACE MID-INFRARED SPECTROSCOPY

使用异步飞秒 OPOS 的 FTIR：高分辨率自由空间中红外光谱的新范例

基本信息

批准号：
EP/H018190/1
负责人：
Derryck Reid
金额：
$ 44.31万
依托单位：
Heriot-Watt University
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=EP%2FH018190%2F1
关键词：
FTIR USING ASYNCHRONOUS FEMTOSECOND OPOS

项目摘要

This proposal for an EPSRC-NPL Postdoctoral Research Partnership addresses the call theme identified as, Photonic Technologies for Optical Remote Sensing in Carbon Capture and Storage and Other Climate Change Applications, and will be conducted in partnership with Dr Tom Gardiner, head of NPL's Environmental Measurement Group.Using their unique infrared differential absorption LIDAR (DIAL) system, NPL's Environmental Measurement Group carries out remote monitoring for the qualification of airborne emissions from industrial installations such as land-fill repositories, petrochemical stacks, cement factories etc. Such quantitative monitoring is an essential procedure in the government's compliance - via carbon taxes imposed on polluters - with the reductions in CO2 and CH4 emissions mandated by the Kyoto Protocol.While being a mature technique, infrared DIAL has reached the limits of its detector technology, and moreover is seriously constrained by its inability to simultaneously measure different gases, a direct consequence of the use of two narrow-linewidth laser wavelengths in the technique. DIAL lacks the ability to obtain true spectroscopic information in a single measurement, and therefore cannot benefit from the sophisticated analysis tools that exist in FTIR to extract the concentrations of multiple species from an absorption spectrum. A system combining the bandwidth and spectral resolution of FTIR, with the remote-sensing facility of DIAL would enhance and extend NPL's technical capability to monitor the emissions of greenhouse gases implicated in climate change.We propose to address this requirement by combining...(a) our world-leading work in femtosecond (fs) FTIR spectroscopy (we were the first group to demonstrate the technique)(b) our world-leading expertise in mid-infrared OPO frequency combs (again, we were the first group to demonstrate a fs OPO frequency comb)Normally FTIR spectroscopy is carried out with thermal sources (globars etc) that produce poorly collimated IR beams that are incompatible with free-space propagation over extended distances. By contrast, the output from a fs OPO has a broad IR bandwidth, approaching that of a thermal emitter, but - critically - has the spatial coherence of a laser, permitting free-space propagation over long distances. A fs OPO therefore provides a route to implementing free-space FTIR across several hundred cm-1 in a single measurement - sufficient to probe the characteristic absorption lines of many chemical species in a single measurement.Conscious of the practical challenges of implementing an interferometric technique over long distances, we propose a novel technical approach, to implement a robust, no-moving-parts FTIR system, which we will progress, in stages, from a bench-top demonstrator to a free-space field-trial at NPL's Teddington site.The concept is based around replacing a mechanically-scanned optical delay line with two asynchronous, phase-coherent mid-IR pulse sequences derived from identical OPOs. Uniquely, this approach is robust, and has the potential to acquire a high (< 0.01 cm-1) resolution spectrum in only a few milliseconds. It offers precisely range-gated detection over propagation distance of potentially 100's of metres, and perhaps further using infrared time-correlated single-photon-counting detection (a technique which the project will have access to at Heriot-Watt).In comparison with DIAL, the technique offers greater spectral discrimination and the ability to simultaneously probe for multiple gases. Furthermore, it is all-solid-state, providing a potentially more compact and efficient solution than DIAL, and avoids the use of dye laser technology, eliminating the associated carccarcinogen hazard. It will extend sensing to new chemical species where suitable DIAL lines are unavailable, and is compatible with heterodyne / RF lock-in detection techniques for improved signal:noise performance.

EPSRC-NPL博士后研究合作伙伴关系的这一提议解决了被确定为“碳捕获和储存以及其他气候变化应用中的光学遥感光子技术”的呼叫主题，并将与NPL环境测量组负责人Tom加德纳博士合作进行。使用他们独特的红外差分吸收激光雷达（DIAL）系统，NPL的环境测量小组对工业装置（例如垃圾填埋场、石化烟囱、水泥厂等。这种定量监测是政府合规的一个重要程序--通过对污染者征收碳税--随着京都议定书要求的CO2和CH 4排放量的减少，红外DIAL虽然是一种成熟的技术，但已经达到了其检测器技术的极限，而且还受到其不能同时测量不同气体的严重限制，这是在该技术中使用两个窄线宽激光波长的直接结果。DIAL缺乏在单次测量中获得真实光谱信息的能力，因此无法受益于FTIR中存在的复杂分析工具，以从吸收光谱中提取多个物质的浓度。将FTIR的带宽和光谱分辨率与DIAL的遥感设备相结合的系统将增强和扩展NPL监测气候变化中涉及的温室气体排放的技术能力。(a)我们在飞秒（fs）FTIR光谱方面的世界领先工作（我们是第一个展示该技术的团队）（B）我们在中红外OPO频率梳方面的世界领先的专业知识（再一次，我们是第一个演示fs OPO频率梳的小组）通常FTIR光谱是用热源进行的（globar等），其产生与延伸距离上的自由空间传播不兼容的准直差的IR光束。相比之下，fs OPO的输出具有较宽的红外带宽，接近热发射器的带宽，但关键是具有激光的空间相干性，允许长距离的自由空间传播。因此，飞秒OPO提供了一种在单次测量中实现数百cm-1的自由空间FTIR的途径-足以在单次测量中探测许多化学物质的特征吸收线。意识到在长距离上实现干涉技术的实际挑战，我们提出了一种新的技术方法，以实现一个强大的，无移动部件的FTIR系统，我们将继续发展，分阶段进行，从台式演示器到在NPL的泰丁顿场地进行的自由空间现场试验。该概念基于用两个来自相同OPO的异步相位相干中红外脉冲序列替换机械扫描的光学延迟线。独特的是，这种方法是鲁棒的，并且具有在仅几毫秒内获得高（< 0.01 cm-1）分辨率光谱的潜力。它提供精确的距离选通探测，传播距离可能为100米，也许还使用红外时间相关单光子计数探测（该项目将在Heriot-Watt使用的一种技术）。此外，它是全固态的，提供了一个可能比DIAL更紧凑和有效的解决方案，并避免使用染料激光技术，消除了相关的致癌物质危害。它将传感扩展到新的化学物种，其中合适的DIAL线不可用，并与外差/ RF锁定检测技术兼容，以改善信号：噪声性能。