| The chalcogenide glass(Ch G)fiber has excellent charaters of wide-spectrum transmission and highly nonlinear in the mid and far infrared,and it has possessed potential wide applications in the fields of fiber sensing,infrared imaging,and fiber lasers.At present,the widest supercontinuum(SC)source has been reported in chalcogenide optical fibers.However,it is difficult to produce high energy output due to the power threshold of material.Multicore fibers have a larger mode field area than single-core fibers,which can increase the input power.At the same time,the threshold of nonlinear effects such as Brillouin scattering in multicore fibers can be effectively reduced.In this paper,Ch G fibers are combined with a multicore fiber structure.The multicore fibers based on Ge-As-Se-Te and Ge-As-Se show the great potential in wide spectrum and high energy transmission in the future.At present,a lot of reports on mid-infrared multicore fiber are mainly focused on the large mode field area to achieve high energy transmission,and most of the researches are in the simulation stage,lack of experimental verification.In this paper,preforms were prepared by highpurity Se-based and Te-based glasses as the core glass of the fiber,respectively.Two new types of extrusion methods are designed on the basis of the traditional extrusion method,and two Ch G seven core fibers with different structures are presented for the first time.Then,based on the multicore preform,a secondary extrusion technique is performed to realize a single-mode seven core fiber.Finally,the optical properties of multi-mode and sigle-mode seven core fibers in the near and far field output energy distribution and supercontinuum generation are given detailed.The first chapter of this paper briefly introduces the classification and applications of the multicore fiber.Then,research history,current status,and future development of the multicore fiber are given in detial,along with their methods for preparing Ch G fibers.The reasons for choosing the extrusion method in this paper is also given.Finally,the purpose and the content of the research on Ch G multicore fiber are pointed out.In the second chapter,the basic characteristics of Ch G glass and theory of multicore fiber are introduced,such as infared transmission spectrum,impurities and defects and energy threshold characteristics.The coupling mode theory is used to analyze the structure,transmission and energy coupling between each core of the fiber.The third chapter mainly introduces the preparation of high-purity Ch G glass and fiber,here two methods for preparing seven-core multicore fiber preform are invented,that including raw material purification,glass melting,glass annealing processing and testing.Two methods of sevencore multicore fiber preform extrusion are introduced in detail,which are based on the methods of isolated extrusion and peeled-off extrusion.In the fourth chapter,the performance of As-Se,Ge-As-Se,and Ge-As-Se-Te Ch G multimode seven-core multicore fibers areuncovered.The loss spectra,near-field energy distribution,and power transmission characteristics of these fibers are analyzed in detail.The effects of different wavelengths and material loss spectra on supercontinuum in optical fibers are discussed.The fifth chapter introduces the single-mode CHG seven-core fiber,that was prepared by the methods ofdouble-isolated and stacked extrusion based on Ge-As-Se glass host.The near-field energy distribution was observed and various optical properties were analyzed.Finally,it is verified that the multicore fiber possess excellent abilities of wide laser transmission window and high power supercontinuum generation.The commercial softwares of finite element software COMSOL and RSOFT were adopted to calculate the effective mode field area,dispersion and fiber coupling.In the last part of the paper,a summary of the full paper is given.Some deficiencies in the research on Ch G multicore fiber were given,and accompanied with solutions of suggestion in the further. |
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