Multiple filament’s formation on a long atmospheric path was studied for an amplitude modulation of the terawatt femtosecond beam with the four and six hole masks. Filaments appeared at the distance that is determined by the Fresnel lens formed by a hole, not by the self focusing theory for the unrestricted (Gaussian like) beam. This lens focuses 1/3 of the energy passing through the hole to the beam spot ≈1 mm in diameter. The robust multifilament array 10–15 m in length was observed if the energy per hole was ≈1-1.5 mJ (pulse duration 50 fs), while each hole produces bundle of a few filaments at higher energies.

中文翻译：

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来自太瓦飞秒光束的长距离鲁棒复丝阵列

使用四孔和六孔掩模对太瓦飞秒光束进行幅度调制，研究了长大气路径上多丝的形成。灯丝出现的距离是由孔形成的菲涅耳透镜决定的，而不是由不受限制的（高斯状）光束的自聚焦理论决定的。该透镜将 1/3 的能量通过孔聚焦到直径约 1 毫米的束斑上。如果每个孔的能量约为 1-1.5 mJ（脉冲持续时间 50 fs），则观察到长度为 10-15 m 的稳健复丝阵列，而每个孔以更高的能量产生几束丝。