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提出了一种精确评估光学薄膜损伤阈值的方法。放大的自发辐射(ASE)光源由于时间相干性和空间相干性较差,所以在近场区域光场强度分布均匀,聚焦后远场也没有被非均匀调制。采用ASE光束作为光学元件损伤阈值测试的辐照光源,可以提高辐照光源的均匀度,实现对光学薄膜损伤阈值的精确评估。ASE光源由神光II高功率激光装置的一级钕玻璃棒状放大器输出,脉宽经过光电开关调制后为9ns,能量输出在几毫焦耳到几十焦耳范围内可调节,光谱半峰全宽(FWHM)为1nm。根据标准ISO-11254,实验获得ASE测试TiO2高反膜的损伤阈值为15.1J/cm2,高于激光测试样品的损伤阈值7.4J/cm2(脉宽为9ns时),更准确地评估了样品的损伤阈值。
A method of accurately evaluating the damage threshold of optical thin film is proposed. The amplified spontaneous emission (ASE) light source has a uniform distribution of light field intensity in the near field due to the time coherence and spatial coherence, and the far field after the focusing is not uniformly modulated. Using ASE beam as the irradiation light source for the damage threshold test of the optical element can improve the uniformity of the irradiation light source and achieve an accurate evaluation of the damage threshold of the optical film. The ASE light source is delivered by a Neodymium glass rod amplifier of a SG high-power laser device. The pulse width is 9 ns after being modulated by a photoelectric switch. The energy output can be adjusted within a few millijoules to tens of joules. The full- FWHM) is 1 nm. According to the standard ISO-11254, the damage threshold of TiO2 high-contrast film obtained by ASE test was 15.1J / cm2, which was higher than the damage threshold value of 7.4J / cm2 (pulse width 9ns) of laser test sample. Damage threshold.