The results of experimental and theoretical study of the self-action of femtosecond optical vortices in the region of anomalous group velocity dispersion in fused silica and fluorides are presented. Multiple filamentation of an axially asymmetric annular beam with a phase dislocation of topological charge m = 1 at a wavelength of 1800 nm in a LiF crystal is investigated. It is found that for the experimentally recorded intensity profile of a vortex beam with two maxima on the diameter, the critical self-focusing power is approximately two times larger than the critical power of a unimodal Gaussian beam. In pulses with supercritical power in the vicinity of the intensity maxima, two coupled filaments, separated by a phase dislocation, are formed on the annular profile of the optical vortex, which prevents energy exchange during their formation. The length of vortex-beam plasma channels in a single pulse is found to be about 300 μm at a diameter of about 2 μm, which is close to the characteristics of plasma channels in a Gaussian beam.

中文翻译：

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熔融石英和氟化物中中红外波长范围内光学涡旋的飞秒多重丝化

介绍了熔融石英和氟化物中异常群速度色散区域中飞秒光学涡旋自作用的实验和理论研究结果。具有拓扑电荷相位错位的轴不对称环形梁的多丝化米= 1 在 1800 nm 的波长下，在 LiF 晶体中进行了研究。发现对于直径上有两个最大值的涡旋光束的实验记录强度分布，临界自聚焦功率大约是单峰高斯光束的临界功率的两倍。在强度最大值附近具有超临界功率的脉冲中，在光学涡旋的环形轮廓上形成了两个耦合的灯丝，它们被相错分开，这阻止了它们形成过程中的能量交换。发现单脉冲涡旋束等离子体通道的长度约为 300 μm，直径约为 2 μm，这接近于高斯束中等离子体通道的特性。