正常色散高非线性石英光纤优化设计及平坦光频率梳产生  

Design of normal dispersion high nonlinear silica fiber and generation of flat optical frequency comb

作　　者：王佳强 吴志芳 冯素春[1] Wang Jia-Qiang;Wu Zhi-Fang;Feng Su-Chun(Key Laboratory of All Optical Network and Advanced Telecommunication Network,Ministry of Education,Institute of Lightwave Technology,Beijing Jiaotong University,Beijing 100044,China)

机构地区：[1]北京交通大学光波技术研究所,全光网络与现代通信网教育部重点实验室,北京100044

出　　处：《物理学报》2022年第23期296-307,共12页Acta Physica Sinica

基　　金：中央高校基本科研业务费专项资金(批准号:2021JBM002);国家自然科学基金(批准号:61827818,62275012)资助的课题.

摘　　要：本文对一种纤芯折射率分布呈三角形的四包层结构正常色散平坦高非线性石英光纤进行优化设计,用于平坦光频率梳产生.研究了光纤各包层宽度和折射率大小对光纤色散特性、截止波长的影响.经过优化设计的光纤在波长1400—1700nm范围内可实现较为平坦的近零正常色散,色散范围为−3—0ps/(km⋅nm).光纤有效模场面积约为11μm^(2),非线性系数可达12.8W^(−1)⋅km^(−1).基于电光调制脉冲泵浦正常色散平坦高非线性石英光纤,进行平坦光频率梳产生仿真.研究了光纤长度、二阶色散、三阶色散、脉冲峰值功率、脉冲宽度、脉冲初始啁啾、脉冲形状等参数对光频率梳产生的影响.仿真结果有利于促进正常色散高非线性石英光纤的国产化及其在平坦光频率梳的应用.The scheme of generating optical frequency comb mainly includes mode-locked laser,electro-optic modulation comb,nonlinear Kerr micro-resonator comb,and nonlinear supercontinuum comb.For the nonlinear supercontinuum comb scheme,the silica-based high nonlinear fiber with near-zero flattened normal dispersion is required.However the fiber dispersion varies along the fiber due to the fabrication inaccuracy.Furthermore,nonlinear supercontinuum comb generation based on the nonlinear fiber has not been systematically studied.In this paper,an optimal design of four-clad flat normal dispersion high nonlinear silica fiber with a triangular core refractive index distribution for the flat optical frequency comb generation is carried out.The effects of the fiber cladding width and refractive index on the fiber dispersion characteristics and cut-off wavelength are studied through using the finite element method mode solver.The optimally designed fiber can obtain relatively flat near-zero normal dispersion in a wavelength range of 1400-1700 nm,the dispersion range is-3-0 ps/(km⋅nm),and the dispersion slope is close to 0 at nearly 1550 nm.The effective mode field area of the nonlinear silica fiber is about 11μm^(2),and the nonlinear coefficient can reach 12.8W^(−1)⋅km^(−1).Based on the electro-optic modulation pulse pumping the flat normal dispersion high nonlinear silica fiber,the flat optical frequency comb generation is systematically simulated with the generalized nonlinear Schrödinger equation.The time-frequency evolutions of a hyperbolic secant pulse,a Gaussian pulse and a super Gaussian pulse are simulated by using the X-Frog technology.The time-frequency spectrograms connect the time domain and the frequency domain of the pulse,clearly showing the change of pulse chirp during the propagation.The effects of various parameters on the optical frequency comb are studied,such as the fiber length,second-order dispersion,third-order dispersion,pulse peak power,pulse half width,pulse initial chirp,and pulse shape.An op

关 键 词：高非线性光纤 光学频率梳 正常色散 自相位调制 

分 类 号：TN253[电子电信—物理电子学]