热交换法掺钛蓝宝石晶体生长过程中内辐射传热对晶体热应力的影响

摘要/Abstract

摘要： 掺钛蓝宝石晶体(Ti∶Al₂O₃,简称钛宝石)是实现飞秒超短脉冲激光和拍瓦级超强超短激光器的核心材料。采用热交换法(HEM)生长大尺寸优质钛宝石激光晶体时,内辐射传热对晶体生长过程中的热量输运、温度及热应力分布具有显著影响,最终影响晶体质量。因此,本文采用有限体积法求解热交换法钛宝石晶体生长过程中晶体和熔体的内辐射传热,采用基于位移的热弹性应力模型求解晶体热应力,详细研究了内辐射传热对晶体温度及热应力分布的影响规律。数值模拟结果表明,内辐射传热显著强化晶体、熔体内的热量输运,导致晶体底部等温线密集分布,温度梯度和热应力显著升高。此外,随着晶体吸收系数(掺杂浓度)增大,晶体底部热应力呈现先升高后降低的非单调性变化规律。随着熔体吸收系数增大,晶体底部温度梯度和热应力略微降低。而随着晶体散射系数增大,晶体底部温度梯度和热应力逐渐降低,当晶体散射系数大于晶体吸收系数时,降低趋势变得显著。

关键词: 掺钛蓝宝石, 内辐射传热, 热应力, 数值模拟, 热交换法, 激光晶体

Abstract: Titanium-doped sapphire crystal (Ti∶Al₂O₃, Ti∶sapphire) is the core material for the development of ultra-fast ultra-high-power laser systems. During the high-quality large-size Ti∶sapphire crystal growth process by heat exchanger method (HEM), internal radiation heat transfer has a significant impact on the heat transport, temperature and thermal stress distributions, and ultimately affects the crystal quality. Therefore, in this paper, the finite volume method is employed to simulate the internal radiation heat transfer within the Ti∶sapphire crystal and melt, while a displacement-based thermoelastic stress model is used to calculate the thermal stress in the crystal. The effects of internal radiation heat transfer on the temperature and thermal stress distributions were investigated in detail. The results show that internal radiation heat transfer significantly enhances the heat transport in the crystal and melt, resulting in dense distribution of isotherms at the bottom of the crystal and a significant increase of temperature gradient and thermal stress in this region. In addition, the thermal stress at the bottom of the crystal first increases and then decreases with the increase of the crystal absorption coefficient (doping concentration). As the absorption coefficient of the melt increases, the temperature gradient and thermal stress at the bottom of the crystal decrease slightly. As the scattering coefficient of the crystal increases, the temperature gradient and thermal stress at the bottom of the crystal gradually decrease. However, this influence is only important after the scattering coefficient is larger than the absorption coefficient.

Key words: titanium-doped sapphire, internal radiation heat transfer, thermal stress, numerical simulation, heat exchanger method, laser crystal

中图分类号:

O782

于行, 赵琪, 齐小方, 马文成, 徐永宽, 胡章贵. 热交换法掺钛蓝宝石晶体生长过程中内辐射传热对晶体热应力的影响[J]. 人工晶体学报, 2024, 53(7): 1212-1221.

YU Hang, ZHAO Qi, QI Xiaofang, MA Wencheng, XU Yongkuan, HU Zhanggui. Effect of Internal Radiation Heat Transfer on the Thermal Stress in Growing Ti∶Sapphire Crystal by Heat Exchanger Method[J]. JOURNAL OF SYNTHETIC CRYSTALS, 2024, 53(7): 1212-1221.

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