Rajeev P P, Gertsvolf M, Simova E, Hnatovsky C, Taylor R S, Bhardwaj V R, Rayner D M, Corkum P B
National Research Council of Canada, Ottawa, Canada, K1A 0R6.
Phys Rev Lett. 2006 Dec 22;97(25):253001. doi: 10.1103/PhysRevLett.97.253001. Epub 2006 Dec 18.
We demonstrate a shot-to-shot reduction in the threshold laser intensity for ionization of bulk glasses illuminated by intense femtosecond pulses. For SiO2 the threshold change serves as positive feedback reenforcing the process that produced it. This constitutes a memory in nonlinear ionization of the material. The threshold change saturates with the number of pulses incident at a given spot. Irrespective of the pulse energy, the magnitude of the saturated threshold change is constant (approximately 20%). However, the number of shots required to reach saturation does depend on the pulse energy. Recognition of a memory in ionization is vital to understand multishot optical or electrical breakdown phenomena in dielectrics.
我们展示了在强飞秒脉冲照射下，块状玻璃电离所需的阈值激光强度逐次降低。对于二氧化硅，阈值变化起到正反馈作用，强化了产生该变化的过程。这构成了材料非线性电离中的一种记忆效应。阈值变化会随着给定位置入射脉冲的数量而饱和。无论脉冲能量如何，饱和阈值变化的幅度是恒定的（约20%）。然而，达到饱和所需的脉冲次数确实取决于脉冲能量。认识到电离中的记忆效应对于理解电介质中的多次光学或电击穿现象至关重要。
