【作者】 彭杨；

【导师】 陆启生； 侯静；

【作者基本信息】 国防科学技术大学 ， 光学工程， 2012， 博士

【摘要】 表面等离子体共振因其对环境折射率变化非常敏感的特性，在光学传感领域有着诸多优点和广阔的应用前景；近十多年来，光子晶体光纤的研究飞速发展，已经在光纤传感领域展现出了巨大的潜能；将结构灵活的光子晶体光纤和高灵敏度的表面等离子体共振技术相结合，为光学传感带来了一股新的活力，吸引了越来越多学者的关注。论文主要围绕表面等离子体共振以及光子晶体光纤在光学传感中的应用开展理论和实验研究。主要内容包括：1、对金属介电常数随温度变化的计算进行了修正，提出利用表面等离子体共振实现温度控制反射率的方法。在Kretschmann结构中的金属膜上涂覆高热光系数的聚合物材料，考虑结构中各种材料折射率以及金属膜厚度随温度的变化，利用特征矩阵法进行了数值计算，得到表面等离子体共振反射率曲线随温度的变化。计算结果显示，波长为532nm的p偏振光分别以70o角和75o角入射时，在10～90oC范围内调节温度，可实现反射率在52.8%～41.5%和31.1%～18.8%范围内的调节。2、建立模型推导得到了同轴电介质－金属薄膜－电介质结构中表面等离子体激元的色散方程。在这种结构中各阶模式都发生了分裂，形成了高折射率高损耗和低折射率低损耗的两种模式，该模型为理解同轴电介质－金属薄膜－电介质结构表面等离子体激元模式的传播提供了直观的图像。用色散方程计算了0.5～1.5μm波长范围内各阶模式的等效折射率以及传输损耗，并将结果与有限元法数值模拟得到的结果进行对比分析，两者吻合得很好。根据计算结果，文章还进一步分析了色散方程的适用范围。3、设计了三种基于光子晶体光纤的表面等离子体共振传感器。前两种为包层外镀膜结构，一种金属膜与待测介质直接接触，用于折射率传感，另外一种金属膜外涂覆高热光系数的敏感层，用于温度传感；第三种为光子晶体光纤空气孔内壁选择性镀膜的温度传感器。在包层外镀膜结构中，可以通过控制光子晶体光纤中空气孔塌缩程度来控制纤芯模式与金属表面等离子体激元模式的耦合。采用有限元法模拟计算了光纤外所镀金属膜厚度、空气孔塌缩程度等参数对传感器损耗谱的影响，模拟计算结果表明，采用波长检测的工作方式，这种类型的传感器对水性介质折射率测量灵敏度能够达1700nm·RIU-1，采用含氟聚合物作为热敏材料，其温度传感灵敏度能够达到200pm/oC以上。第三种传感器中，光纤包层的第二层孔中填充了高热光系数的液体，其中部分孔内壁镀上了金属膜。温度的变化将影响纤芯基模与表面等离子体模式之间的耦合，从而使光纤的损耗谱发生改变。讨论了传感器各部分材料，包括金属膜、填充液体和熔融石英，介电常数随温度的变化，通过数值计算分析了传感器的模场分布和损耗谱，模拟表明该结构温度传感的灵敏度能达到720pm/oC。4、提出并实现了一种基于选择性液体填充光子晶体光纤的温度传感器。研究了一种放射状混合光子晶体光纤（radially hybrid photonic crystal fiber）结构，光子晶体光纤中环绕纤芯的第一圈孔内填充了高折射率的溶液，外圈仍为空气孔。分析了这种结构光纤的传输特性，重点讨论了最内圈高折射率柱的类带隙作用，研究发现光纤吸收损耗对填充液体折射率非常敏感。模拟计算了注入光纤中金溶胶的吸收谱及其随温度的变化，结果表明温度对其影响很小。利用光子晶体光纤的选择性空气孔塌缩技术和液体填充技术，制作了最内圈孔填充高折射率二甲基亚砜和水性金溶胶混合溶液的光子晶体光纤。搭建了光纤热光特性的测量系统，实验测量了选择性液体填充PCF损耗谱随温度的变化，在538nm和666nm附近分别有两个损耗峰，峰值波长与温度之间基本成线性关系，在20～28oC范围内，得到了高达-5.5nm/oC的灵敏度。该实验同时首次证实了放射状混合光子晶体光纤中类带隙作用的存在。更多还原

【Abstract】 As the surface plasmon resonance (SPR) is highly sensitive to the variations in therefractive index of the surrounding dielectrics, it has many advantages and wide rangeof applications in optical sensing. With the rapid development of photonic crystal fibers(PCF) in the recent decade, it has shown great potential in fiber optic sensing.Combining of the highly sensitive SPR technology with PCF bings new vitality to theoptical sensing and has attracted increasing attentions. The applications of surfaceplasmon resonance and photonic crystal fiber in optical sensing are investigated intheory and experiment in this thesis. The primary contents are presented as follows:1. The calculation of the temperature dependence of the dielectric function of metalis modified. A method for controlling the reflection index of mirror by using the surfaceplasmon resonance is proposed. A polymer film with high thermooptic coefficient iscoated on the metal film in the Kretschmann configuration. The variation of metal filmthickness and dielectric constants for all layers with temperature are calculated, and thedevice proposed is numerically simulated by using the characteristic matrix method.The results of the simulation show that when the incident wavelength is532nm, and thetemperature is controlled between10oC and90oC, the reflection index can becontrolled from52.8%to41.5％for70oincident angle and31.1%to18.8%for75oincident angle.2. The dispersion equation of coaxial dielectric-metal-dielectric structure isestablished. Each mode splits into a high effective refractive index branch and a loweffective refractive index branch. An intuitive picture that allows for a qualitativeunderstanding is provide in this model. The effective refractive indexes and propagationlosses of the modes are calculated by using the analytical dispersion expression. They fitwell with the numerical simulation results obtained by using finite element method from0.5μm to1.5μm. According to the simulation results, the applicability of the dispersionrelation is analyzed.3. Three kinds of surface plasmon resonance sensor based on the photonic crystalfiber are proposed. The first two kinds are based on the photonic crystal fiber withmetallic coating on the cladding. One with the metal film directly contacting with theanalyte for refractive index sensing, another with a sensing layer with largethermo-optic coefficient coating on the metal film for temperature sensing. The thirdone is a temperature sensor based on the photonic crystal fiber with selectively metalliccoating in the air holes. In the cladding coated structure, the coupling of fiber coremodes and surface plasmon modes can be controlled by the air holes collapsing inphotonic crystal fiber. The effects of metal film thickness and air hole diameter on theloss spectrum of the sensor are simulated by using finite element method. With a spectrum based detection methods,respectively， the refractive index sensitivity1700nm/RIU (refractive index unit) can be achieved for an aqueous analyte, and temperaturesensitivity above200pm/oC can be achieved for a fluoropolymer temperature sensinglayer. In the third sensor, the air holes of the second layer are filled with a largethermo-optic coefficient liquid and some of those air holes are selectively coated withmetal. Temperature variations will induce changes of coupling efficiencies between thefundamental core mode and the plasmonic mode, thus leading to different loss spectrathat will be recorded. In this paper, variations of the dielectric constants of allcomponents, including the metal, the filled liquid and the fused silica, are considered.We conduct numerical calculations to analyze the mode profile and evaluate the powerloss, demonstrating a temperature sensitivity as high as720pm/oC.4. A temperature sensor based on a selective liquid filled photonic crystal fiber isproposed and demonstrated. A radially hybrid photonic crystal fiber is studied. The firstring around the core is filled with liquids of higher refractive index than the matrix, theouter rings being composed by air holes. The propagation properties of the fiber andbandgap-like effect of the high refractive index ring are analyzed. Absorption lossspectra of the fiber are found to be quite sensitive to the refractive index of liquid. Theabsorption spetrum of the gold colloids and the temperature effect on it are calculated,and the temperature effect is found to be very small. compact temperature sensor basedon a selectively-liquid-filled PCF is proposed. A photonic crystal fiber with the firstring around the core filling with a mixture of dimethyl sulphoxide and aqueous goldcolloids is fabricated, with the controlled hole collapse and liquid injecting technologyof photonic crystal fiber. A experiment system for measuring the thermo-opticproperties of the fiber is set up. The variations of the loss spectrum with thetemperatures are measured. Two loss peaks appears on the loss spectrum near538nmand666nm. The relationship between the maximum loss wavelength and temperature isapproximately linear.Temperature sensitivity up to-5.5nm/oC is achieved. Thebandgap-like effects are also confirmed in the experiment.更多还原