Study of the pulse-to-pulse interaction optimizing the cutting of high-repetition fs-laser systems in medicine

飞秒激光在生物组织内的脉冲对脉冲相互作用几乎是完全了解的：如果与引起的效应(等离子体形成、冲击波、空化气泡)相比，时间脉冲间隔很大，并且如果生物组织没有任何限制，可以假设生物组织由水或至少是含水的液体组成。因此，对晶状体组织，特别是角膜组织切割的平均质量、效率和副作用的预测并不是真正可预测的，往往只是根据每个单独的应用经验确定的。挑战在于描述和比较这些不能完全再生介质和组织的非常快的过程，同时施加几个后续的和在其机械效应上暂时重叠的激光脉冲。到目前为止，还没有给出从单幅图像产生一系列图像所需的重复性。目前，这种研究是通过在水或水介质中的阴影摄影来进行的，在这种情况下，为了避免不方便的空间维度和时间尺度，通常使用ns-激光脉冲。玻璃体、晶状体或角膜中单个空化气泡的动力学尚未发表。结论不是从基础实验中得出的，而是仅从实际切割试验中得出的，例如在猪眼上或在动物研究中进行的切割试验。零星的泵浦-探测实验或昂贵的滚筒或高速摄像机作为替代。随着现有实验的扩展，将首次在组织中显示两个或更多相互作用的激光诱导光学击穿的动力学，时间尺度在纳秒范围内。为此，通过记录来自单个事件的一系列图像，利用LED闪光实现彩色编码的曝光序列，并将其映射到sCMOS传感器的不同空间区域。通过自适应光学系统同时消除系统诱导的像差，实现了不同组织和组织样本的高度可比性，这反过来又允许推导出更一般的陈述。

The pulse-to-pulse interaction of fs-laser inside biological tissue is only almost completely understood: if temporal pulse separations are large compared to the effects induced (plasma formation, shock wave, cavitation bubble), and if the biological tissue without any restrictions, can be assumed to consist of water or at least an aqueous liquid. Thus, predictions of average quality, efficiency and side effects of cuts in e.g. crystalline lens tissue and especially corneal tissue are not really predictable and often simply determined empirically for each individual application. The challenge is to describe and compare these very fast processes in not completely regenerating media and tissue while applying several subsequent and in their mechanical effects temporally overlapping laser pluses. So far, the necessary reproducibility to create a series of pictures from single images is not given.Currently, such investigations are performed by means of shadow-photography in water or aqueous media, in this context, to avoid inconvenient spatial dimensions and time scales often ns-laser-pulses are used. The dynamics of a single cavitation bubble in the vitreous, lens or cornea is not yet published. Conclusions are not drawn from basic experiments, but only from actual cutting tests, e.g. performed on porcine eyes or in animal studies. Sporadically pump-probe experiments or expensive drum or high-speed cameras are used as an alternative.With an extension of the existing experiment, for the first time, the dynamics of two or more interacting laser-induced optical breakdowns will be shown in tissue with time scales in the nanosecond range. For this, a chromatically coded exposure sequence is realized with LED flashes and mapped to different spatial regions of a sCMOS sensor, by this recording a series of images from a single event. With the simultaneous elimination of system-induced aberrations by an adaptive optics system a high degree of comparability for different tissues and tissue samples is achieved, which in turn allows the deduction of a more general statement.