Research On THz Inspection Technology And Surface Enhanced Raman Scattering Photonic Crystal Fiber Sensor

THz inspection and surface enhanced Raman scattering PCF sensor are two main constituent parts of modern photonics field. THz imaging is an important compensation for other imaging technologies, also THz-TDS and remote sensing are significant technologies in atmosphere pollution inspection.Surface enhanced Raman scattering has got sufficient recognition and utilization since it was discovered. It has incomparable advantages in ultra-low concentration, even single molecule sample inspection. PCF's unique structure can provide a novel ideal substrates for SERS sensor, and further broaden the application fields of it.The main contents and innovations can be concluded as follows:1. Researched on THz-CW scanning imaging. Designed a novel THz-CW scanning image system, by recording transmission light to get distinct image for polyporous metal platelet concealed under cloth, and spatial resolution could be 0.7 mm. So we can draw a conclusion that this system is feasibility and full of application value.2. Designed on SERS substrates. Arithmetic simulaton for silver nano- particles with different structures, separation distances and sizes, so as to optimize SERS substrates were carried on. The result indicated that, at 785 nm wavelength, the silver sphere with r = 38 nm, stick with r = 50 nm and hemisphere with r = 25 nm has the best SERS effect; for three nanoparticles there are greatest enhanced factor(GSERS) when separation distance is 0.5 nm, Gsphere>Gstick>Ghemisphere respectively; Gsphere and Ghemisphere decrease with separation distance's increase.3. Designed a novel index guiding PCF, whose core is surrounded by six large air holes symmetrically. According to the simulation result, solid core PCF with large holes rlarge = 11μm , rsmall = 1μm , (?)20μm , cladding air holes r = 1μm , pitch (?)=3μm can have mode area of 25.8μm².4. Designed a novel band gap PCF suitable for SERS sensor. By simulation for different structure HCPCF, PCF with core air hole r_core = 3.2μm , cladding air holes r_clad = 0.65μm , and (?)=1.65μm is suitable for SERS sensor at (?)=785 nm.5. Experiment on SERS PCF sensor. Proposed two ways of coating film inner core hole of PCF, namely ion sputtering and nanoparticles suspending in analyte solution to realize ultra low concentration inspection. In order to improve SERS effect, tapering function of fiber fusion splicer was utilized to collapse the cladding air holes while keep core air hole open, as a result only the core hole was filled with analyte solution while cladding holes was still filled with air. Besides, injection under negative air pressure was proposed to accelerate interaction between analyte and exciting light. The analytes of Pyridine and Melamine were used to test the performance of this system and got the ideal experiment results.