基于柚子型光子晶体光纤长周期光栅的痕量TNT爆炸物探测原理与方法研究

Explosives detection is increasingly attracting more interest due to the global increase in terrorism. Highly selective and sensitive sensing techniques are required in order to face the serious challenge from the rapid identification of explosive. Due to its very low vapor pressure TNT explosive is very difficult to detect in the gas phase. To address this problem, a novel rapid chemical vapor sensor based on long period gratings (LPGs) formed in grapefruit photonic crystal fiber (GPCF) with large air-holes coated with a sensitive thin-film is proposed as a promising platform for detection of trace vapor TNT. When TNT vapor molecules flow through the large air-holes in the cladding of GPCF, they are absorbed by the sensitive thin-film to cause the change in film refractive index. The effect will result in a change in the effective index of cladding mode of the fiber, and hence, a shift in the resonant wavelength. In this subject, the sensing principle of GPCF-LPGs sensor with embedded sensitive film is analyzed. A great effort is made in study related to the fabrication of coatings deposited on the inner holes of GPCF. An optofluidic assembly is designed to enable both gas flow and light transmission measurements through PCF-LPGs structure optically coupled with single mode fiber. The all-fiber gas sensing system including GPCF-LPGs-based refractive index sensor is constructed and the capability of the GPCF-LPGs in rapid, selective, and sensitive detection of trace TNT explosive is demonstrated.

随着恐怖主义日益增加，爆炸物探测引起世界关注，因此急需先进的传感技术以解决爆炸物快速识别所面临的安全挑战。但是爆炸物如梯恩梯(TNT)等因其极低的蒸气压在气相很难被检测。提出一种基于柚子型光子晶体光纤长周期光栅(GPCF-LPGs)的气体传感新原理与方法，用于痕量TNT爆炸物蒸气的快速探测。拟在具有长周期光栅结构的柚子型光子晶体光纤包层空气孔中形成一层对TNT蒸气选择性敏感的薄膜，TNT分子能引起敏感膜折射率变化并导致光纤包层模有效折射率变化，通过实时监测光纤光栅谐振波长变化实现痕量TNT爆炸物检测。项目在对"GPCF-LPGs-敏感膜"气体传感原理进行详细研究的基础上，获取敏感物质在包层空气孔上成膜的方法，采用光流控技术设计光纤传感元件，建立基于GPCF-LPGs包层空气孔内敏感膜折射率变化的TNT爆炸物气体传感新方法，以期实现对爆炸物气体快速、高灵敏和高选择性探测。

爆炸物及相关材料的感测科学和技术对于国土安全和国家防御有着至关重要的地位，并且随着恐怖主义活动日益增加，爆炸物探测引起世界关注，因此急需先进的传感技术以解决爆炸物快速识别所面临的安全挑战。本课题研究出一种基于光子晶体光纤的传感新原理与方法，用于痕量二硝基甲苯(DNT)或2,4,6-三硝基甲苯(TNT)爆炸物蒸气的快速探测。设计和制作出“柚子型光子晶体光纤长周期光栅”与“光子晶体光纤同轴马赫-曾德尔干涉仪”两种传感器构型，在光子晶体光纤包层空气通道中形成一层对硝基苯类爆炸物蒸气选择性敏感的薄膜，硝基苯类爆炸物分子能引起此敏感膜结构和折射率变化并导致光纤包层模式有效折射率变化，通过实时监测传输光谱谐振波长变化实现痕量硝基苯类爆炸物检测。其中，制作的柚子型光子晶体光纤长周期光栅传感器对DNT检测限为50ppb，光子晶体光纤同轴马赫-曾德尔干涉仪传感器对TNT检测限为0.2ppb。此类传感器具有不受电磁干扰、灵敏度高、响应速度快、重量轻、结构紧凑、使用灵活、适于在腐蚀性或危险性环境应用等优点，有望成为一个很有应用前景的传感平台。相关研究成果我们已形成12篇学术论文分别发表在《OPTICS EXPRESS》、《SENSORS AND ACTUATORS B》、《OPTICAL ENGINEERING》等本领域权威期刊与SPIE国际会议上，同时申请发明专利1项。该课题的研究为基于光子晶体光纤的传感技术理论与器件增添了新内容，具有较大学术价值。