铌酸锂晶体的温控光束偏转及其应用

发布时间：2018-03-09 13:38

本文选题：铌酸锂晶体　切入点：温度梯度　出处：《哈尔滨工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：铌酸锂晶体是一种集多性能于一体的多功能材料,其中包括铁电、压电、电光、光折变性能等,它具有非常良好的热稳定性和化学稳定性。利用提拉法生长的铌酸锂晶体容易加工而且成本较低,生长尺寸较大,是未来发展中一种重要的功能材料。目前,光束偏转现象是最近几年比较感兴趣的热门话题,主要利用晶体的电光效应实现光束的偏转,最近研究的热门晶体主要包括坦铌酸钾、铌酸锂等以及掺杂的相似晶体。铌酸锂晶体的电光偏转现象也已经被研究,但是由于铌酸锂的介电常数只有28.7,而坦铌酸钾晶体则是15000。所以,在相同条件下,想要达到和其他晶体同样的偏转效果,铌酸锂晶体需要加入的电压是KTN晶体的500倍。因此,我们考虑利用温场来实现晶体内的光束的偏转。论文主要研究了铌酸锂晶体在温场条件下实现光束偏转,我们主要研究了不同厚度、不同位置以及不同的电极方式下晶体内部的光束偏转的实验,并且利用实验结果设计了光开关和分束器两个光学器件。通过实验的测量结果可以看出,晶体内部的偏转角度随着晶体上施加电压的增加而逐渐增大。当施加在晶体上的电压增大时,晶体内部的温度场也会随之增加。在测量的实验结果中,1 mm厚上下两层全面镀电极的铌酸锂晶体的偏转角度可以达到2度以上,实现一维上的偏转;同时,研究了1 mm厚单面镀电极的对比实验,研究发现,由于电极改变导致光束的偏转产生了二维的变化,但是最大的偏转角度只有接近1度;3 mm厚全面两面镀电极的晶体的偏转角度和1 mm厚的单面电极的晶体产生了相似的二维变化,偏转角度可以接近1度,由于晶体的厚度的改变,晶体内光束的偏转随着光束入射位置的变化可以实现二维的偏转;最后,我们将钛电极镀在3 mm厚的铌酸锂晶体的侧面,通过这种改变,可以看出温场在晶体的传播方向,实验得到了较理想的偏转角度。在此基础上我们对比了电极的变化对温场和光束偏转角度的影响,从实验结果可以看出,随着电极的减小,晶体内部产生的温度场也随之减小,偏转角度也会随之减小。光开关和分束器是光学领域中两个重要的光学器件,我们利用温场控制光束偏转的实验实现了光开关,以及一维和二维的分束。实验测量了光开关和分束器的各光束的功率,实验得到的结果与理论基本符合,随着半波片的转动,光强也会产生从无到有的变化。
[Abstract]:Lithium niobate crystal is a kind of multifunctional materials which include ferroelectric, piezoelectric, electro-optic, photorefractive, etc. It has very good thermal stability and chemical stability. Lithium niobate crystal grown by Czochralski method is easy to process, low cost, large growth size, and is an important functional material in the future. Beam deflection is a hot topic in recent years, which mainly uses the electro-optic effect of crystal to deflect the beam. The electrooptic deflection of lithium niobate crystals has also been studied, but the dielectric constant of lithium niobate is only 28.7and the dielectric constant of potassium tanniobate crystal is 15000. therefore, under the same conditions, To achieve the same deflection effect as other crystals, lithium niobate crystals require a voltage of 500 times that of KTN crystals. We consider using the temperature field to realize the beam deflection in the crystal. In this paper, we mainly study the beam deflection of lithium niobate crystal under the condition of temperature field, we mainly study the different thickness. The experiment of beam deflection in crystal at different positions and different electrode modes is carried out. Two optical devices, optical switch and beam splitter, are designed based on the experimental results. The angle of deflection inside the crystal increases with the increase of the applied voltage on the crystal. The temperature field inside the crystal will also increase. In the measured experimental results, the deflection angle of lithium niobate crystal with 1 mm thickness and 1 mm thickness can reach more than 2 degrees, realizing the deflection in one dimension, at the same time, The contrast experiment of 1mm thick single-sided plating electrode is studied. It is found that the beam deflection is caused by the change of the electrode. However, the maximum deflection angle is only close to 1 degree and 3 mm thick, and the deflection angle of the crystal with 1 mm thickness is similar to that of one side electrode with 1 mm thickness, and the deflection angle can be close to 1 degree. Because of the change of the thickness of the crystal, the deflection of the beam in the crystal can be realized with the change of the incident position of the beam. Finally, the titanium electrode is coated on the side of the lithium niobate crystal with a thickness of 3 mm. It can be seen that the temperature field propagates in the crystal direction, and the ideal deflection angle is obtained experimentally. On this basis, we compare the effect of the electrode change on the temperature field and the beam deflection angle. From the experimental results, we can see that with the decrease of the electrode, The temperature field inside the crystal also decreases and the deflection angle decreases. Optical switch and beam splitter are two important optical devices in the field of optics. We have realized the optical switch by using the experiment of controlling beam deflection by temperature field. The power of each beam of the optical switch and beam splitter is measured experimentally. The experimental results are in good agreement with the theory. With the rotation of the half-wave plate, the light intensity will also change from scratch to existence.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O734

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