超快激光与生物含水组织相互作用

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。

Investigation on the Mechanism of Ultrashort Pulse Laser Interacting with Soft Tissues

The mechanism of ultrashout laser interacting with biological tissues was investigated in detail and a moedl has been developed to calculate irradiance thresholds for laser induced optical breakdown in biological soft tissues.Calculation results has shown that for nanosecond or subnanosecond laser pulses,initial heating electrons in strongly absorbing media contributes significantlu to avalanche ionization and optical breakdown threshold decreases with increasing tissue absorbance;for subpicosecond laser pulses,multiphoton ionization is the main mechanism for optical breakdown which is unsensitive to linear absorption.When reached breakdown thweshold,laser energy deposited in thin layer with thickness of 1um.For laser energy much higher than breakdown thershold,the effective lighg penetration depth decreased.