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光学铌酸锂 (LiNbO3 )晶体是目前应用最广泛 ,工艺较为成熟的集成光学衬底材料。利用光学LiNbO3 晶体的非线性可产生倍频、和频、差频、四波混频和参量振荡等效应 ,可以拓宽光波长的范围 ,并开辟新的激光光源。在信号处理方面 ,可实现波前畸变补偿 ,光信号的处理与控制、光调制、光开关、光偏转、图像放大、光计算、光记忆等。我们采用提拉法 ,用Si Mo棒加热生长出了高质量的5 3× 1 80mm光学y轴LiNbO3 晶体。由于沿y轴方向生长晶体时 ,z轴与x轴结构的不对称性 ,再加上生长速率、热膨胀系数等不一致 ,在引晶放肩阶段易出杂棱 ,在拉断降温过程中易放电开裂。针对这些问题 ,我们采取了以下措施 :( 1 )设计了一个合适的温场 ,温场下部温梯适中且不会随坩埚中液面下降而明显减小 ,温场上部温梯很小。( 2 )确定了合理的生长工艺参数。在 3mm/h拉速下使晶体底部微凹。( 3)确定了降温速率及退火工艺以保证晶体不致在降温或退火过程中开裂。( 4)采用了特殊的极化工艺对晶体进行单畴化处理。
Optical lithium niobate (LiNbO3) crystal is currently the most widely used, more mature technology integrated optical substrate material. The nonlinearity of the optical LiNbO3 crystal can produce the effects of frequency doubling, sum frequency, difference frequency, four-wave mixing and parametric oscillation, which can broaden the range of optical wavelengths and open up new laser light sources. In signal processing, wavefront distortion compensation, optical signal processing and control, optical modulation, optical switching, optical deflection, image amplification, optical computing, optical memory and so on can be realized. We use the Czochralski method to grow a high quality 5 3 × 1 80mm optical y-axis LiNbO3 crystal with Si Mo rods. As the growth along the y-axis crystal, the z-axis and the x-axis structure of the asymmetry, coupled with growth rate, coefficient of thermal expansion and other inconsistencies in the lead crystal placed shoulder prone to miscellaneous edges, easy to discharge in the pull off the cooling process Cracking. In response to these problems, we have taken the following measures: (1) A suitable temperature field is designed. The temperature gradient in the warm field is moderate and will not decrease obviously with the liquid level in the crucible. The temperature gradient in the upper part of the temperature field is very small. (2) to determine a reasonable growth process parameters. The bottom of the crystal is dithered at a pull rate of 3 mm / h. (3) Determine the cooling rate and annealing process to ensure that the crystal will not crack during cooling or annealing. (4) Using a special polarization process on the crystal single-domain treatment.