中红外硫系光子晶体光纤偏振分束器的设计与研究

第3章蝶形双芯光子品体光纤偏振分束器特性分析ABSTRACTSulfur compounds have attracted much attention in recent years because of theirproperties,such as lower softening temperature,better fiber formation,highernonlinear refractive index and light transmittance in mid-infrared and near-infraredbands,compared with quartz glass.For example,the photonic crystal fiber preparedwith sulfur compounds as the base material can break through the limitation that thequartz medium can only work below the wavelength of 2 um all the time,and it hassignificant applications in the fields of light pulse laser at mid-infrared band,therealization of all-optical network and biomedicine.In order to realize stable all-opticalnetwork,polarization beam splitter is one of the indispensable optical devices.Based on the above background,the polarization splitter of mid-infrared sulfurseries photonic crystal fiber is studied and discussed in this paper.The effect of fiberstructure on the coupling length,bandwidth and extinction ratio of the splitter isdiscussed by using the basic theory of optical waveguide and finite elementsimulation.Three kinds of polarization splitter of sulfur photonic crystal fiber inmiddle infrared band are designed and optimized.1.A butterfly photonic crystal fiber polarization splitter with a base material ofGaS was studied.The influence of fiber structure on the characteristics of the splitterwas discussed by using COMSOL Multiplicity software through finite elementsimulation.A high-performance mid-infrared band polarization splitter was realizedby optimizing the structure parameters.When located in the mid-infrared window of4 um,the beam splitter length is 45.4 dB,extinction ratio reaches -117 dB,and thebandwidth reaches 400nm when extinction ratio is less than or equal to-20 dB.Thecorresponding wavelength range is 3.8dB to 4.2dB,which plays an important role inall-optical network and micro-nano optics.2.Study a basal material for three elliptic Kong Shuang core photonic crystalfiber polarization beam splitter,by referencing the three elliptic air holes in the fibercore structure symmetry is broken,obtain high birefringence characteristics,using theoptical waveguide theory and finite element method simulation of fiber structure onthe beam splitter are discussed the influence of various characteristics,through theoptimization of structure parameters,implementation when located in 4um of infrared2