基于薄膜铌酸锂光波导的平坦光频率梳的设计  

Design of Flat Optical Frequency Comb Based on Lithium Niobate Optical Waveguide

作　　者：刘宇[1] 邓宜 卫航 吴春将 冯素春[1] Liu Yu;Deng Yi;Wei Hang;Wu Chunjiang;Feng Suchun(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：《中国激光》2021年第13期16-28,共13页Chinese Journal of Lasers

基　　金：国家自然科学基金(61827818,62075008);中央高校基本科研业务费专项资金(2021JBM002)。

摘　　要：提出了一种基于正常色散薄膜铌酸锂集成非线性波导产生高重复频率平坦光学频率梳的方案,并进行了数值仿真研究。采用3.6 m长正常色散薄膜铌酸锂集成非线性波导,通过色散调控优化设计,基于正常色散,利用自相位调制和光波分裂作用,在1550 nm附近仿真得到了3 dB带宽约为32 nm的平坦光学频率梳。利用X-Frog技术分析了双曲正割、高斯和超高斯三种不同输入脉冲在传播过程中的时频演化情况。研究了各种参数对光学频率梳带宽和平坦度的影响,并研究了光学频率梳的相干性。仿真结果表明,薄膜铌酸锂集成非线性波导在1550 nm波段高重复频率平坦相干光学频率梳的产生方面具有较好的应用前景。Objective The optical frequency comb generation schemes mainly include mode-locked laser, electro-optic modulation comb, nonlinear Kerr micro-resonator comb, and nonlinear supercontinuum-based comb. For the nonlinear supercontinuum-based comb scheme, flat optical frequency comb generation has been extensively studied, which is based on self-phase modulation and optical wave breaking in silica-based high nonlinear fibers(HNLFs) with near-zero flattened normal dispersion. The dispersion of the silica-based HNLFs needs to be near zero in the normal dispersion regime to generate the flattened and broadened spectrum. Furthermore, several hundred meters long silica HNLFs are required because of their relatively low nonlinearity coefficients. However, such a long fiber causes dispersion variation along the fiber owing to the fabrication inaccuracy. Herein, high repetition rate flat optical frequency comb generation based on normal dispersion lithium niobate(LiNbO3) optical waveguides is proposed and numerically analyzed. The 3.6-m-long cavity-less nonlinear LiNbO3 optical waveguide with normal dispersion can be used to solve the dispersion variation problem in the HNLFs. The repetition rate of the proposed optical frequency comb can reach 10--50 GHz owing to the electro-optic modulator tunable optical pulse source, and the waveguide structure and parameters used in the simulation are achievable using current technologies. The proposed optical frequency comb has potential applications in astronomy, optical communication, and microwave photonics. The parameters influencing optical frequency comb performances, time-frequency evolution mechanism, and spectral coherence are also analyzed, which provides a detailed guideline for flat optical frequency comb generation.Methods Firstly,the dispersion and nonlinear coefficient of the LiNbO3 waveguide are obtained using the finite element method mode solver.Then,the time-frequency evolution process of the pulse in the waveguide is simulated with the generalized nonlinear Schr9 din

关 键 词：非线性光学 铌酸锂 光学频率梳 自相位调制 光波分裂 

分 类 号：TM252[一般工业技术—材料科学与工程]