1 064 nm Laser Damage on Indium Tin Oxide Films
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摘要: 液晶光学器件在激光光束精密控制上具有重要应用前景，氧化铟锡（ITO）薄膜作为液晶光学器件的透明导电电极，是液晶器件激光损伤的薄弱环节。为此，建立了ITO薄膜激光热损伤物理模型。理论计算结果表明：1 064 nm激光对ITO薄膜的损伤主要为热应力损伤；连续激光辐照下，薄膜损伤始于靠近界面的玻璃基底内；脉冲激光辐照下，温升主要发生在光斑范围内的膜层，薄膜损伤从表面开始。利用泵浦探测技术，研究了ITO薄膜的损伤情况，测量了不同功率密度激光辐照后薄膜的方块电阻，结合1-on-1法测定了ITO薄膜的50%损伤几率阈值。实验结果表明：薄膜越厚，方块电阻越小，激光损伤阈值越低；薄膜未完全损伤前，方块电阻随激光功率密度的增加而增大。理论计算与实验结果吻合较好。设计液晶光学器件中的ITO薄膜电极厚度时，应综合考虑激光损伤、透光率及薄膜电阻的影响。Abstract: Liquid crystal optical elements have important applications in laser facility, and the indium tin oxide (ITO) films are generally used in liquid crystal optical elements as transparent conductive electrodes. Laser induced damage of ITO films leads to failure of liquid crystal optical elements. The laser damage model of ITO films which simulates the temperature distribution and thermal stress distribution was established. The laser damage of ITO films was experimented through pump-probe technology, and the power density producing damage at a probability of 50% (i.e., damage threshold) was obtained by 1-on-1 testing, and the square resistance of the film after laser irradiation was also measured. The experimental data basically agree with the simulated results. The results show that 1 064 nm laser damage of ITO film occurs mainly by thermal stress. The damage of ITO film begins from K9 glass substrate after CW laser irradiation, while the damage begins from the surface of ITO film after pulsed laser irradiation. Furthermore, the laser damage thresholds decrease with the increase of thickness of ITO films. The square resistance of ITO films increases with the increase of laser intensity unless the ITO films have been damaged completely. The optimal thickness of ITO film in liquid crystal optical element depends on the factors of laser damage, transparence and square resistance.
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