高功率激光系统中随机分布缺陷产生的“热像”

摘要

Based on the diffraction theory model of hot-images,the formation mechanism of the hot-images induced by the defects with random size and position distribution in a high power laser system is theoretically investigated by using the propagation matrix of the spatial spectrum.For the comparison with the theoretical results,the evolution of the hot-images induced by defects with random distribution is also numerically investigated.Furthermore,the relationship describing the tendency of the hot-image intensity with the number or size range of the defects is analyzed by employing statistical theory.The results show that the hot-image intensity will reach a maximum if the size of the corresponding defect approaches a specific value,and that there exists a corresponding relation between the transverse position of the hot-image point with the maximum intensity and the defect distribution.It is also found that the intensity of the hot-image has an upward trend with both the size range and the number of defects within a certain scope increasing.However,the tendency will be steady when the probability of the defects with the most risk of damage size reaches a certain value.Such results maybe provide a guidance for improving cleanliness of the optical components.%基于＂热像＂的衍射理论模型,并利用空间频谱的传输矩阵,理论分析了位置和尺寸均随机分布的缺陷在高功率激光系统中产生＂热像＂的机理,作为理论分析结果的对比验证,数值模拟了高功率激光束受到这种随机分布缺陷调制后所形成＂热像＂的演化规律,进而从统计平均的角度讨论了＂热像＂强度的变化趋势与缺陷分布数目和尺寸范围之间的关系.结果表明,当缺陷的尺寸接近某个特定值时,受其调制的光束会形成强度最大的＂热像＂点,且＂热像＂所在平面强度极大值点的横向位置与光学元件表面的缺陷横向分布相对应;在一定范围内,＂热像＂的强度最大值随着缺陷数目和尺寸范围的增加而增加,但当最具风险尺寸的缺陷在元件表面出现的概率达到一定程度后将趋于稳定.这可为确定元件表面的洁净度要求提供一定的参考.