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Study On The Terahertz Continuous Wave Imaging And Photonic Crystal Fiber Based On Surface Plasmon Resonance Sensor

Posted on:2012-02-07Degree:DoctorType:Dissertation
Country:ChinaCandidate:P B BingFull Text:PDF
GTID:1118330362453730Subject:Physical Electronics
Abstract/Summary:PDF Full Text Request
Terahertz wave (THz) has wide application prospect for its unique characteristics in the fields of time-domain spectroscopy, imaging, communication, scrutiny, exploration, astronomy and so on, among which THz imaging is the most promising. With the development of the THz imaging, the bottleneck of the popularization of the THz imaging is how to get brief, quick and cheap system. We build a THz continuous wave (CW) transmission imaging system based on scanning, which can effectively solve these problems.In sensor field, the photonic crystal fiber (PCF) sensor based on surface plasmon resonance (SPR), possessing both the excellent transmission characteristics of PCF and highly sensitive characteristics of SPR simultaneously, is very suitable for sensing. We investigate two PCF-SPR sensors with different structures, and carry out PCF-SPR sensor experiments on LMA series.The main contents and key creative points of this dissertation are as follows:1. A THz CW transmission imaging system based on scanning is built. The THz transmission image can be required by scanning point by point and recording the intensity of THz information behind the sample. The speed of imaging is high because of no need time delay device and pause during scanning process. Thanks to the corresponding two-dimensional electronically controlled high-precision translation stage, we can image samples of different sizes. THz imaging can also be carried out with different resolutions according to various needs. So the system with simple structure, easy operation, fast data acquisition capability and relatively low cost has broad application prospects and promotion of value.2. The effect factors of image are analyzed and high-quality THz CW scanning imaging is researched. Eventually, maximum resolution of the THz image can reach 0.4mm with the THz wavelength of 118.8μm, the spot size of 1.8mm and the step length of 0.25mm. Image quality can be comparable with THz focal plane array camera. Utilizing this system, we carried out some representative samples of contrast imaging, and the results are satisfying.3. Several common computational methods of PCF are introduced, especially finite element method (FEM) is focused on. FEM can match perfectly matched layer (PML) and calculate the PCF-SPR sensor. Based on the typical structure of the PCF-SPR sensor, a PCF-SPR sensor with large size microfluidic channels is proposed. The structure of the PCF is simple and easy to manufacture. It is propitious for metal coating and infiltration of microfluidic. The contact area of sample and metal film is increased, and the interface is closer to the core, so the energy coupling between the plasmon mode and the core-guided mode is easier. The refractive index of microfluidic can be measured effectively.4. Based on the hollow core photonic bandgap (PBG) PCF, a PCF-SPR temperature sensor with glycerin liquid filled in the air core is proposed. Since glycerin has high refractive index, the transmission type of PCF will be changed from PBG to total internal reflection (TIR) by this design, which can significantly broaden the scope of transmission. The refractive index of glycerin changes linearly with temperature within a certain temperature range. The refractive index of glycerin can be detected by measuring the transmission light and thus the ambient temperature at this time can be obtained. This design takes full advantage of large core air hole of hollow core PCF, because we just fill microfluidic and film in core air hole, it is easy to control the uniformity of coating.5. Most research on the PCF-SPR sensor is still on theoretical stage, for the difficulty of manufacturing designed PCF, coating metal nanofilm, microfluidic infiltration in micro core hole of PCF and achieving continuous broadband coherent light source. We conducted experiments with PCF of LMA series produced by the NKT Photonics. Several different methods are used for metal coating in air cladding holes of PCF. Bromine tungsten lamp is selected as light source and continuous broadband fiber-coupled output can be achieved. A spectrometer is used to detect the continuous broadband spectrum of light and the effect is obvious.
Keywords/Search Tags:terahertz continuous wave imaging, photonic-crystal-fiber, surface-plasmon-resonance, sensor, finite element method
PDF Full Text Request
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