Department of Quantum Electronics, Vilnius University, Saulėtekio Avenue 9, Building 3, LT-10222 Vilnius, Lithuania.
Dipartimento di Scienza e Alta Tecnologia, Università degli Studi dell'Insubria, Via Valleggio 11, I-22100 Como, Italy.
Phys Rev Lett. 2014 May 16;112(19):193901. doi: 10.1103/PhysRevLett.112.193901. Epub 2014 May 12.
We present a detailed experimental investigation which uncovers the nature of light bullets generated from self-focusing in a bulk dielectric medium with Kerr nonlinearity in the anomalous group velocity dispersion regime. By high dynamic range measurements of three-dimensional intensity profiles, we demonstrate that the light bullets consist of a sharply localized high-intensity core, which carries the self-compressed pulse and contains approximately 25% of the total energy, and a ring-shaped spatiotemporal periphery. Subdiffractive propagation along with dispersive broadening of the light bullets in free space after they exit the nonlinear medium indicate a strong space-time coupling within the bullet. This finding is confirmed by measurements of a spatiotemporal energy density flux that exhibits the same features as a stationary, polychromatic Bessel beam, thus highlighting the nature of the light bullets.
我们进行了详细的实验研究，揭示了在反常群速色散区克尔非线性体介质中自聚焦产生光子弹的本质。通过对三维强度分布的高动态范围测量，我们证明了光子弹由一个高度局域化的高强度核心组成，该核心携带自压缩脉冲，包含大约 25%的总能量，并具有环形时空边缘。光子弹在离开非线性介质后在自由空间中沿亚衍射传播并展宽，表明在子弹内存在强烈的时空耦合。这一发现通过测量时空能量密度通量得到了证实，该通量表现出与稳定的多色贝塞尔光束相同的特征，从而突出了光子弹的本质。
