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研究了超快脉冲激光与生物组织相互作用的机理 ,建立了生物软组织中激光诱导光学击穿模型 ;结果表明 ,对于纳秒或亚纳秒脉冲激光 ,强吸收介质的热电子发射对电子雪崩电离过程有很大影响 ,等离子体光学击穿阈值随生物组织吸收的增加而降低 ;在激光脉宽为亚皮秒量级时 ,多光子电离成为光学击穿的主要机制 ,介质的击穿阈值几乎与线性吸收系数无关。在达到光学击穿阈值时 ,激光能量沉积在厚度约 1μm的薄层之内 ;随着激光能量显著超过击穿阈值 ,有效的激光透过深度减小。
The mechanism of the interaction between ultra-fast pulsed laser and biological tissue was studied, and laser-induced optical breakdown model in biological soft tissues was established. The results show that for nanosecond or sub-nanosecond pulsed lasers, the effect of thermionic emission of strong absorption medium on electron avalanche ionization The threshold of plasma optical breakdown decreases with the increase of biological tissue absorption. When the laser pulse width is sub-picosecond, multiphoton ionization is the main mechanism of optical breakdown. The dielectric breakdown threshold is almost Irrespective of linear absorption coefficient. When the optical breakdown threshold is reached, the laser energy is deposited within a thin layer with a thickness of about 1 μm; the effective laser penetration depth decreases as the laser energy significantly exceeds the breakdown threshold.