高重复频率激光脉冲光束大小对吸收玻璃损伤特征的影响

针对高重复频率对吸收性滤光片损伤问题,研究了高重复频率(kHz量级)激光脉冲的光束半径大小对吸收玻璃的形貌特征和损伤机理.研究发现在总的激光作用个数、单脉冲能量和脉冲作用频率固定时,吸收玻璃的损伤特性发生很大变化:在光束半径较大时,激光能量分散,主要损伤形貌是熔化破坏;随着光束半径的减小,激光脉冲能量变得集中,热量的累积效果变得明显,逐渐变成熔化破坏和气化破坏;当激光光束半径小到一定程度,则会由于光强过大使得介质表面发生击穿而产生激光等离子体冲击波,同时由于热量沉积的集中使光束作用中心处产生超热液体,当满足相爆炸发生的条件时,气化物、液滴和固体颗粒的混合物会向外飞溅,在损伤凹陷的周围形成气化物、液滴的冷凝区和固体颗粒溅射区.关键词：激光诱导损伤高重复激光脉冲吸收玻璃相爆炸

Influence of the high-repetition-pulsed laser beam size on the damage characteristics of absorbing glass

The influence of the beam size of pulsed laser on damage morphology of absorbing glass, as well as the mechanism of the damage produced by high-repetition-pulsed laser (kHz magnitude), is investigated. We show that the damage morphology changes greatly with the decrease of the beam size under the condition that the energy of each individual pulse,the number of the pulses incident on the glass and the repetition frequency are kept invariant. The damage is induced by melting of the glass material due to dispersed energy of the incident laser with large beam size. With decreased beam size of laser, the material will break resulting from the melting and evaporating of glass induced by the densing and increasingly deposited laser energy in glass material. When the beam size is further reduced, too intensive laser will penetrate the dielectric material on the surface of glass. As a result, the laser induced plasma shock wave occurs. In addition, the super-heated liquid at the center where the laser beam interacts with glass will be produced as a consequence of the tremendous deposited laser energy. When the threshold of phase explosion is reached, the mixture of the evaporated, melted and original solid materials will blast outwards. Consequently, characteristic morphology made up of three regions covered with solid granules of original glass material and the re-crystallized material of the evaporated and melted glass will form around the damage crater.