Thermally-induced catastrophic optical breakdown is clearly of great importance for fiber-based laser-light delivery systems. Fiber core can be destroyed irreparably at rates of 1 m/s by breakdown that starts at a locally heated point and travels back towards the laser; that the damage tracks left behind are often elegantly uniform and periodic is only a slight recompense. Breakdown can occur at relatively modest intensities (we have recorded 2.8 mW/µm in a multimode fibre at blue/green wavelengths), and has been observed in many different fibres at both Ar+ and Nd:YAG laser wavelengths. We initiate the effect by heating the fibre with a small flame whilst the laser light is propagating within it. A solitary thermal shock-wave is created which propagates along the fibre towards the laser, leaving the core permanently damaged and unable to guide light. Associated with this shock-wave is a bright spot of side-scattered light which can be observed propagating along the fibre; for this reason we have named the effect the "fibre-fuse". Similar thermal shock-waves have previously been seen in gases ("laser-induced deflagration waves")
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机译:热诱导的灾难性光学击穿显然对于基于光纤的激光传输系统非常重要。从局部加热点开始向着激光行进的击穿会以1 m / s的速率无可挽回地破坏光纤芯。留下的损坏痕迹通常是优雅而均匀的,只是周期性的。击穿可能发生在相对适度的强度下(我们在蓝/绿波长的多模光纤中记录到2.8 mW / µm),并且在Ar +和Nd:YAG激光波长下的许多不同光纤中都观察到了击穿。当激光在光纤中传播时,我们通过用小火焰加热光纤来启动效果。产生了一个单独的热冲击波,该冲击波沿着光纤朝着激光传播,使纤芯永久损坏,无法导光。与该冲击波相关的是侧向散射光的亮点,可以观察到它沿着光纤传播。因此,我们将这种效果称为“纤维熔丝”。以前已经在气体中看到类似的热冲击波(“激光诱发的爆燃波”)
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