高功率脉冲激光对阶跃折射率多模光纤损伤机理

 理论分析和模拟仿真研究了激光点火系统中光纤端面损伤、光纤初始输入段损伤和光纤内部损伤机理。结果显示：端面损伤主要是由光纤端面的杂质和缺陷引起；光纤初始输入段损伤是由光束的初次反射造成光纤局部激光能量密度增大引起的；光纤内部体损伤主要由于激光自聚焦效应引起损伤和光纤受到的意外应力产生微小碎片，吸收激光能量，引起光纤局部损伤。给出了激光点火系统中提高光纤损伤阈值的一般方法，主要包括光纤端面处理、设计合理的激光注入耦合装置。

High power pulsed laser-induced damage to step-index multimode optical fibers

By theoretical analysis and simulation,laser-induced damage mechanisms of fiber's end face,entry segment and fiber inside are studied.The admixtures and defects on the fiber end face induce the damage;the first reflections along the fiber core/cladding interface induce the damage of entry segment.The unexpected stress and beam self-focus in optical fibers induce the internal damage.In this case a portion of the fiber cross section experiences significant tensile stresses which aggravate defects within the fused silica,including microcracks at the fiber boundaries which were initially produced during the fiber drawing process.Damage at these locations is always catastrophic,usually resulting in a complete break across the fiber cross section,The methods of increasing fiber damage threshold are also summarized in the paper.