Study On The Surface Plasmon Resonance Technology And Its Applications In Photonic Crystal Fiber Sensing

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.