Study On The Raman Gain Characteristics Of Chalcogenide Glass Fiber

In recent years,the infrared Raman fiber lasers more than 2?m in military defense,biomedical,infrared sensing,species identification,pollutant monitoring,laser communication and other fields have important application prospects,as Raman fiber laser development is an important direction.Compared with common solid and gas lasers,Raman fiber lasers have their unique performance advantages: good beam quality,narrow pulse width,high conversion efficiency,wide spectral range(UV to near infrared),no phase matching,high flexibility and easy to all-fiber system integration.As a new type of optical devices,Raman fiber lasers have been developed rapidly.Working material of traditional Raman fiber lasers is the quartz fiber.For the great phonon energy(>1100cm-1)and the increasing dramatically transmission loss in the long-wave,it is difficult to produce an effective stimulated Raman effect in more than 2?m wavelength.To obtain a mid-infrared laser with the wavelength greater than 2?m,it is required that the fibers have a low phonon energy and a transmission loss in the mid-infrared band.The chalcogenide glasses have very low phonon energy(less than 350cm-1),excellent infrared transmission performance(0.5~1?m to 12~25?m),extremely high linear refractive index(2.2~3.5),nonlinear refractive index coefficient n2(100~1000 times higher than the quartz glass)and ultrashort nonlinear response time(response time is less than 200fs).And the optical and material properties can be controlled by the glass component.It is a new medium-infrared excellent working medium of Raman fiber lasers.Currently reported chalcogenide Raman fiber lasers are made of chalcogenide glass fibers of As2S3 or As2Se3 material.However,due to the high toxicity of As element,the glass preparation,later fiber drawing,testing,use and many other aspects exist serious security risks.It is an urgent need to explore a new non-As environmentally friendly Raman chalcogenide glass fiber material.The study shows that the Ge-Sb-Se system chalcogenide glasses with non-As element have excellent infrared waveguide characteristics and good environmental friendliness.They are excellent fiber candidate substrate for infrared Raman chalcogenide fibers,but study of their Raman gain characterization has not been reported.Based on the theory of solid Raman fiber lasers,a method for calculating the Raman gain coefficient of bulk chalcogenide glasses was proposed.Combined with the Raman spectrum,the glass Raman gain coefficient of Ge-Sb-Se system was obtained for the first time.The influence of the internal network structure on the Raman gain coefficient was studied,and the Ge-Sb-Se glass fibers were drawn by the pipe rod method.The Raman gain test platform of fibers was designed.It provides theoretical and experimental basis for medium-infrared environment-friendly Raman chalcogenide fiber lasers to design.In this paper,the first chapter is the introduction.Firstly,the origin of Raman fiber lasers was briefly introduced.The research progress of Raman chalcogenide fiber lasers at home and abroad was reviewed.The research hotspots were summarized.And the Raman chalcogenide fiber lasers basic theory,working principle and development process were analyzed,and then the research content,purpose and significance of this work were put forward.In the second chapter,the author started with the Maxwell equations and derived the wave equations of the form of pulse transmission.Based on this,the author introduced the SRS effect which was closely related to the third-order nonlinear coefficient.The correlation theory of stimulated Raman scattering and the factors related to the Raman gain coefficient in different pump conditions were summarized.The third chapter mainly introduces the preparation and performance test of chalcogenide glasses,including the introduction of raw materials,the introduction of experimental equipments,the steps of glass melting and the whole process of the later series.The author prepared glass rods of high purity and excellent performance by melt quenching method.Differential thermal analysis(DSC),near infrared imaging,infrared transmission spectroscopy,hardness,refractive index and Raman spectroscopy were measured for the glass slices after cut and polish process.In the fourth chapter,the characteristics of the Raman gain of the Ge-Sb-Se system were introduced from the aspects of theoretical calculation,glass performance test,calculation and analysis of results.In this paper,a method for calculating the Raman gain coefficient of bulk chalcogenide glasses was proposed,and its correctness was verified.Combined with the Raman spectrum of the test,the Raman gain coefficient of Ge-Sb-Se system was obtained for the first time.And the influence of the internal network structure on the Raman gain coefficient was analyzedThe fifth chapter mainly introduces the Raman gain characteristics of chalcogenide fibers from the aspects of preparation of chalcogenide optical fibers,construction of Raman gain test platform and numerical simulation of Raman gain.The Ge-Sb-Se fibers with the clad-core of different composition were successfully drawn by the traditional tube method.The Raman gain comprehensive test platform was designed independently,and the influence of different pump sources on the fiber Raman gain was analyzed by numerical simulation.The final conclusion summarizes the main research results of this paper,and explains the shortcomings in the research process and the problems that need to be studied in the future research work.