| As the study on the silica glass photonic crystal fibers (PCFs) becomes mature andperfect increasingly, people began to research on the soft glass PCFs. Compared withthe silica glass, the soft glass has many incomparable advantages of low transition tem-perature, high linear and nonlinear refractive indexes, and it has high transparency fromthe near-infrared to the mid-infrared. The dual-core and three-core PCFs are expected tobe used as the polarization couplers and the polarization splitters in optical systems. Themulti-core PCFs can extend the effective mode area, which have potential applications inhigh power laser transmission and mode coupling. In this paper, several kinds of the softglassdual-core,three-coreandmulti-corePCFsaredesignedbythemultipolemethod,thefinite element method (FEM) and the beam propagation method (BPM), and then systemresearch the polarization, coupling and mode characteristics of PCFs. The main contentsare as follows:Firstly, the basic characteristics and the applications PCFs are demonstrated, the de-velopments on dual-core and multi-core PCFs and the structural parameters of the softglass are introduced, and some typical numerical simulation method are given.Secondly, based on the mode coupling theory, two kinds of chalcogenide glass highpolarization maintaining dual-core PCFs are designed by using multipole method andFEM, respectively, which can make a perfect combination between the polarization char-acteristics with the coupling characteristics in the mid-infrared band. It provides a theo-retical basis for further developments of new mid-infrared polarization maintaining fibercoupling device.Thirdly, the impact of the structure parameters and the background material on theperformance of polarization splitters is analyzed. It is found that the high birefringencecan increase the difference-value of coupling length in the two orthogonal polarization di-rections, andthenthepolarization-independentpropertyofthesplittercanbeachieved. Inaddition, the excellent dual-core and three-core polarization splitters are designed. Com-pared with the SF57 glass dual-core PCFs, the tellurite glass dual-core PCFs are moresuitableforfabricatingpolarizationsplitter. Atthewavelength =1.55 m,the0.36-mm-long dual-core PCFs can separate the polarization lights from each other. Compared withthe silica glass three-core PCFs, the tellurite glass three-core PCFs have higher extinc- tion ratios and lower coupling loss. Therefore, the tellurite glass dual-core and three-corePCFs have more broad application prospects in the production of polarizing splitters.Finally,accordingtothesuper-modestheory,twokindsofAs2Se3chalcogenideglassmulti-core PCFs are designed. The effective mode area characteristics and the nonlinearcharacteristics have been studied by FEM. It is found that the proposed the multi-corePCFs have high nonlinear and large effective mode area. Therefore, the multi-core PCFsinthepreparationofhigh-powerlasersandothernonlineardeviceshavebroadapplicationprospects. |
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