Plasma mediated ablation of biological tissues with nanosecond-to-femtosecond laser pulses: Relative role of linear and nonlinear absorption
Plasma mediated ablation of biological tissues with nanosecond-to-femtosecond laser pulses: Relative role of linear and nonlinear absorption
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DOI：
10.1109/2944.577302
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发表时间：
1996-12-01
影响因子：
4.9
通讯作者：
Stuart, BC
中科院分区：
文献类型：
--
作者：
Oraevsky, AA;DaSilva, LB;Stuart, BC
在波长为1053 nm、脉冲宽度为1 ns ~ 300 fs的不同激光脉冲宽度范围内，研究了等离子体介导的胶原凝胶和猪角膜的消融。发现透明和弱吸收凝胶的脉冲激光消融总是由等离子体介导的，而强吸收组织的消融仅在超短脉冲范围内由等离子体介导。对于亚纳秒激光脉冲，消融阈值沿着等离子体光击穿阈值随组织吸收率的增加而减小，而对于飞秒激光脉冲，消融阈值与组织线性吸收无关。在纳秒范围的激光脉冲持续时间，光学击穿通过雪崩电离开始进行加热的电子在组织表面的强吸收杂质贡献。在超短脉冲范围内，光学击穿是由被照射介质的多光子电离引发的（在以1053-nm波长照射的组织的情况下为六个光子），并且对线性吸收不太敏感。用亚皮秒激光脉冲获得了对周围材料没有热或机械损伤的高质量消融坑，实验结果表明，亚皮秒等离子体介导的消融可以作为一种工具，精确的激光显微手术的各种组织。
Plasma mediated ablation of collagen gels and porcine cornea was studied at various laser pulse durations in the range of 1 ns-300 fs at 1053-nm wavelength, It was found that pulsed laser ablation of transparent and weakly absorbing gels is always mediated by plasma, On the other hand, ablation of strongly absorbing tissues is mediated by plasma in the ultrashort-pulse range only, Ablation threshold along with plasma optical breakdown threshold decreases with increasing tissue absorbance for subnanosecond pulses, In contrast, the ablation threshold was found to be practically independent of tissue linear absorption for femtosecond laser pulses, The mechanism of optical breakdown at the tissue surface was theoretically investigated, In the nanosecond range of laser pulse duration, optical breakdown proceeds via avalanche ionization initiated by heating of electrons contributed by strongly absorbing impurities at the tissue surface. In the ultrashort-pulse range, optical breakdown is initiated by multiphoton ionization of the irradiated medium (six photons in case of tissue irradiated at 1053-nm wavelength), and is less sensitive to linear absorption, High-quality ablation craters viith no thermal or mechanical damage to surrounding material were obtained with subpicosecond laser pulses, Experimental results suggest that subpicosecond plasma mediated ablation can be employed as a tool for precise laser microsurgery of various tissues.