Specific features of the anti-Stokes band of the light bullet supercontinuum spectrum under filamentation of 1900-nm femtosecond pulses, focused by an axicon in fused silica and calcium fluoride, have been experimentally, numerically, and analytically investigated. It is found that the formation of two or more light bullets in a filament leads to modulation of spectral components' intensity. The oscillation period of spectral components, defined as the wavelength interval between adjacent intensity minima, decreases with decreasing their wavelength. On a logarithmic scale, the relative change in the oscillation period in the spectrum is proportional to the spectral component wavelength and is independent of the pulse energy and the position of the light bullet formation region in the filament. It is established that the modulation in the spectrum is due to the interference of the broadband supercontinuum emitted by light bullets, and its period decreases with increasing interval between them.

中文翻译：

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轴锥聚焦下光弹光谱形成的干涉效应

在 1900 nm 飞秒脉冲的丝状化下，由石英和氟化钙中的轴锥聚焦的轻型子弹超连续谱的反斯托克斯带的具体特征已经通过实验、数值和分析进行了研究。发现在灯丝中形成两个或多个光弹会导致光谱分量强度的调制。光谱分量的振荡周期（定义为相邻强度最小值之间的波长间隔）随着其波长的减小而减小。在对数尺度上，光谱中振荡周期的相对变化与光谱分量波长成正比，与脉冲能量和灯丝中光弹形成区域的位置无关。