极化电极均匀化设计调控铌酸锂周期极化占空比

摘要/Abstract

摘要： 准相位匹配(QPM)理论上能够充分利用晶体的非线性光学系数、无走离效应,在光学频率转换中具有非常大的优势。铌酸锂晶体(LiNbO₃, LN)具有高非线性光学系数、宽通光范围和低生长成本,因此基于铌酸锂铁电畴结构设计获得的周期极化铌酸锂晶体(PPLN)成为准相位匹配技术的理想选择。目前制备PPLN晶体最常用的方法是外加电场极化法,制备过程中,电极结构的参数对极化过程至关重要。本研究基于实时监测下的电场极化过程,结合有限元分析,对不同电极结构的空间电场分布进行分析,发现电极边缘出现电场极大值,而电极内部的电场分布相对均匀。基于这一现象,本文提出了一种多通道电极结构的设计方案,以实现极化空间内部电场的均匀分布。本研究采用十通道电极进行极化实验,通过表征每个通道的占空比,发现内部八个通道的占空比大小均匀且在50%±5%范围,通过晶体的倍频实验验证发现十通道周期极化样品中中间通道相对边缘通道的非线性转换效率明显提升并分布均匀,证明其中间通道具有占空比可控的均匀极化结构,为极化空间电场均匀化设计提供了一种高效合理的设计方案。

关键词: 铌酸锂, 周期极化铌酸锂, 非线性光学, 空间电场分布, 有限元分析

Abstract: In theory, quasi phase match (QPM) can make full use of nonlinear optical coefficient of the crystal, and has no deviation effect, which has great advantages in optical frequency conversion. Lithium niobate crystal (LiNbO₃, LN) has high nonlinear optical coefficient, wide optical range and low growth cost, causing the periodically poled lithium niobate crystal (PPLN) based on the design of ferroelectric domain structure is an ideal choice for QPM. At present, the most commonly used method for fabricating PPLN crystal is applied electric field method. In the fabrication process, the parameters of electrode structure are important for the poling process. Based on the electric field poling process under real-time monitoring and finite element analysis, this paper analyzed the spatial electric field distribution of different electrode structures. It is found that the electric field maximum appears at the edge of the electrode, the electric field distribution inside the electrode is relatively uniform. Based on this phenomenon, a design scheme of multi-channel electrode structure is proposed to achieve uniform distribution of electric field in poled area. By characterizing the duty cycle ratio of each channel, it is found that the duty cycle ratio of the inner eight channels are uniform and within 50%±5%. Through the SHG experiment of crystals, it is found that the nonlinear conversion efficiency of the inner channel relative to the edge channel in the sample of ten-channel periodic poling is significantly improved and uniformly distributed. It is proved that the middle channels have a uniform poling structure with controllable duty cycle, which provides an effective design for generating uniform poling electric fields.

Key words: lithium niobate, periodically poled lithium niobate, nonlinear optics, spatial electric field distribution, finite element analysis

中图分类号:

O734

刘齐鲁, 郑名扬, 高洋, 张龙喜, 宋于坤, 王孚雷, 刘宏, 王东周, 桑元华. 极化电极均匀化设计调控铌酸锂周期极化占空比[J]. 人工晶体学报, 2024, 53(3): 449-457.

LIU Qilu, ZHENG Mingyang, GAO Yang, ZHANG Longxi, SONG Yukun, WANG Fulei, LIU Hong, WANG Dongzhou, SANG Yuanhua. Poling Electric Field Uniformization Design Regulates the Duty Cycle of Periodically Poled Lithium Niobate[J]. JOURNAL OF SYNTHETIC CRYSTALS, 2024, 53(3): 449-457.

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