Research On Nonlinear Effects In Chalcogenide Fibers

Nonlinear fiber optics has been widely applied in the field of all-optical signal processing,such as wavelength conversion,optical signal regeneration,signal multiplexing and demultiplexing,etc.Supercontinuum generation in optical fiber has numerous applications to spectroscopy,optical fiber sensing,optical frequency metrology and communication optical source of multi-channel.However,the intrinsic transmission window in mid-infrared region limits further application of traditional optical fiber in many other field such like military,medicine and biology.Thus it is necessary to find alternative materials possessing the properties of large transmission window and high nonlinearity.In order to maximize the bandwidth of the supercontinuum in mid-infrared region,we study the nonlinear effect and chromatic dispersion in As2Se3 PCF,thus determining the key parameters that govern the design;we also analyze the differences and similarities concerning efficiency of the wavelength conversion based on FWM between chalcogenide fibers and silica fibers.Chalcogenide glass can be transparent from the visible up to the infrared region of around 14?m,and possess nonlinear refractive index up to 1000 times greater than fused silica and fast response time in the femtosecond range which is much faster than semiconductor optical amplifiers(SOA)or saturable absorber(SA).By adjusting the PCF structure,not only it can obtain the ideal dispersion characteristics,but also the endlessly single-mode and high nonlinearity.In order to maxmize the bandwidth of the supercontinuum in the 2 3As Se PCF,we study the dispersion and nonlinearity affected by fiber structure of As2Se3 PCF.By engineering the structure parameters of the fiber,we acquire the relatively flat dispersion curve with a ZDW of 2.5um,extend the stokes caused by FWM to a longer wavelength,and analyze the endlessly single-mode condition in As2Se3 PCF but keep a high nonlinearity and a low loss at the same time.We also investigate the relationship between the effective mode and the loss in the fiber.After comprehensive analysis,we choose the optimum fiber's parameters that can lead a maximum supercontinuum generation.The conclusion is verified by numerical simulation;We obtain the ultra-wide bandwidth of supercontinuum generation and describe the process of the supercontinuum development with evolution diagram of time and frequency domain.A comparison of two kind of fibers-chalcogenide glass and silica glass regarding the efficiency of the wavelength conversion based on FWM near the communication wavelength region is investigated,we conclude that the wavelength conversion tunable bandwidth will reach the largest once the signal locate at long wavelength direction of the ZDW,and the results shows that under the same conditions the efficiency of chalcogenide glass fiber is higher than that of common silica glass fiber.Finally we give the energy flow diagram in chalcogenide fiber in contrast with that in commonly used fiber.And we also present FWM-based wavelength conversion of high-repetition-rate signals at 1 GHz and 20 GHz.