GROC UJI, Departament de Física, Universitat Jaume I, 12080 Castelló, Spain.
Opt Lett. 2012 Mar 1;37(5):957-9. doi: 10.1364/OL.37.000957.
We present a technique for efficient generation of the second-harmonic signal at several points of a nonlinear crystal simultaneously. Multispot operation is performed by using a diffractive optical element that splits the near-infrared light of a mode-locked Ti:sapphire laser into an arbitrary array of beams that are transformed into an array of foci at the nonlinear crystal. We show that, for pulse temporal durations under 100 fs, spatiotemporal shaping of the pulse is mandatory to overcome chromatic dispersion effects that spread both in space and time the foci showing a reduced peak intensity that prevents nonlinear phenomena. We experimentally demonstrate arbitrary irradiance patterns for the second-harmonic signal consisting of more than 100 spots with a multipass amplifier delivering 28 fs, 0.8 mJ pulses at 1 kHz repetition rate.
我们提出了一种在非线性晶体的多个点同时高效产生二次谐波信号的技术。多焦点操作是通过使用衍射光学元件来实现的，该元件将锁模钛宝石激光器的近红外光分成任意光束阵列，这些光束被变换成非线性晶体中的焦点阵列。我们表明，对于持续时间在 100fs 以下的脉冲，必须进行时空脉冲整形，以克服在空间和时间上扩展焦点的色散效应，从而降低峰值强度，防止非线性现象。我们通过使用多通放大器，在 1kHz 重复率下，以 28fs、0.8mJ 的脉冲，实验证明了由 100 多个点组成的二次谐波信号的任意辐照度模式。
