高亮度高平坦度超连续谱光源的宽带光纤腔衰荡传感方法及其应用研究

Broadband cavity ring-down spectroscopy (BB-CRDS) technique is a highly sensitive multicomponent sensing technique, which has shown the extensive application in aspects of multicomponent trace gases detection and so on. It has become a hot research topic in the field of CRDS sensing technique due to the appearance of supercontinuum source recently. However, the trandtional broadband cavity ring-down sensing technique based on supercontinuum source has many disadvantages such as the detection sensitivity of weak spectral components is low due to the unflat supercontinuum source, sensing band is limited by the bandwidth of cavity mirrors, the stability of the sensing system is very likely to degenerate due to the ageing process of the cavity mirror coatings and so on. Therefore, there is an urgent need to develop a high flat supercontinuum source and new broadband cavity. So the project proposes to combine the two technique of the high bright and flat supercontinuum source and the broadband fiber cavity ring-down, which can improve the sensing band, the sensitivity and the stability of the sensing system. The project needs to carry out the sensing theory and sensing characteristics of broadband fiber cavity ring-down sensing technique based on a high bright and flat supercontinuum source, needs to research the key technology such as the low-loss sensor and its multiplexing and so on, needs to verify the new sensing method by doing the multicomponent, multiparameter sensing experiments. Give priority to make breakthroughs in key technologies such as fast and simultaneous detection of the mixed gases of carbon dioxide and methane and so on. There are a great significance in the academic and practical application values to explore the highly sensitive multicomponent, multiparameter sensing technique.

宽带腔衰荡光谱技术是一种高灵敏度多组分传感技术，已在多组分痕量气体检测等方面，展示了极其广泛的应用前景，近年来因超连续谱光源的出现更是使其成为当前腔衰荡传感技术的研究热点。但目前超连续谱光源传统腔衰荡传感存在超连续谱不平坦导致弱谱成分探测灵敏度不高、腔镜带宽限制了传感带宽和腔镜膜层易老化导致传感系统不稳定等问题，迫切需要研发高平坦度的超连续谱光源和发展新型宽带腔。为此，本项目提出将高亮度高平坦度超连续谱光源融入宽带光纤腔衰荡传感技术，提高了传感带宽、灵敏度和稳定度。将开展基于高亮度高平坦度超连续谱光源的光纤腔衰荡传感理论及其传感特性、低损耗实用传感器及其复用等关键技术的研究，并通过多组分、多参量传感实验进行验证，重点突破二氧化碳和甲烷混合气体快速同步检测等关键技术，对于实现高灵敏度多组分、多参量传感技术，具有十分重要的科学研究意义和实际应用价值。

光纤腔衰荡传感技术是一种高灵敏度光谱检测技术，已在痕量气体、压力检测等方面，展示了极其广泛的应用前景，但其灵敏度和稳定度亟待进一步提高，为此，本项目着重开展了可用于宽带光纤腔衰荡技术的高亮度高平坦度超连续谱光源的研究以及基于频移干涉技术的光纤腔衰荡传感方法的研究。在超连续谱光源研究方面，通过优化光纤的结构参数和第一层空气孔填充的液体折射率，设计出了色散平坦的全波段正常色散光子晶体光纤；利用该光纤获得了10 dB带宽为698 nm、相干度大于0.9、平坦度小于8.6 dB 的超连续谱光源；通过优化激光的初始啁啾、调制深度和调制频率，进一步提高了超连续谱光源的平坦度；采用光栅对对高相干度超连续谱脉冲进行压缩，产生了脉宽小于10 fs的超短脉冲，压缩质量高达95.4%。在频移干涉光纤腔衰荡传感技术方面，利用该技术实现了目标气体的成分识别与浓度的同步检测，获得了较好的线性响应和稳定度，灵敏度为263.48 ppm；将该技术与双波长差分吸收技术相结合，使气体灵敏度提高到了105.25 ppm；利用频移干涉光纤腔衰荡技术的复用能力，实验上实现了两个通道气体的同步检测，获得的灵敏度分别为289.69和508.25 ppm；提出了基于频移干涉光纤腔衰荡的压力传感新方法，降低了传感系统的成本，获得了0.02356/(km.MPa)的灵敏度，优于传统的光纤腔衰荡压力传感技术；同时提出了基于频移干涉技术的光纤光栅大规模复用新方法，实验上实现了60个弱光栅位置和反射率的同步检测，并仿真分析了相关参数对复用容量的影响，指出当光源功率为10 mW、光栅间隔10 m时系统的复用容量可达3000个；通过融合频移干涉技术与波分复用技术，实验上实现了363个弱光纤光栅阵列的三波长复用与解调，理论上预测了该混合技术的复用容量可达3207个，若增加复用波长数，复用容量还可进一步增加。本项目取得的研究成果对于推动痕量气体监测、压力探测以及光纤传感器大规模复用的发展及实际应用具有重要的理论意义和科学价值。