Poling Electric Field Uniformization Design Regulates the Duty Cycle of Periodically Poled Lithium Niobate

Abstract

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

CLC Number:

O734

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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