Wang Ningning, Liu Shan, Zhao Ruwei, Xu Tianxiang, Chen Feng, Arie Ady, Krolikowski Wieslaw, Sheng Yan
Opt Lett. 2022 Aug 1;47(15):3656-3659. doi: 10.1364/OL.459405.
Transverse second-harmonic generation, in which the emission angles of the second harmonic are determined by the spatial modulation of the quadratic nonlinearity, has important applications in nonlinear optical imaging, holography, and beam shaping. Here we study the role of the local duty cycle of the nonlinearity on the light intensity distribution in transverse second-harmonic generation, taking the generation of perfect vortices in periodically poled ferroelectric crystal as an example. We show, theoretically and experimentally, that spatial variations of the nonlinearity modulation must be accompanied by the corresponding changes of the width of inverted ferroelectric domains, to ensure uniformity of the light intensity distribution in the generated second harmonic. This work provides a fundamental way to achieve high-quality transverse second-harmonic generation and, hence, opens more possibilities in applications based on harmonic generation and its control.
横向二次谐波产生中，二次谐波的发射角由二次非线性的空间调制决定，在非线性光学成像、全息术和光束整形等方面有重要应用。在此，我们以周期性极化铁电晶体中完美涡旋的产生为例，研究非线性的局部占空比在横向二次谐波产生中对光强分布的作用。我们通过理论和实验表明，非线性调制的空间变化必须伴随着反铁电畴宽度的相应变化，以确保所产生的二次谐波中光强分布的均匀性。这项工作提供了一种实现高质量横向二次谐波产生的基本方法，从而为基于谐波产生及其控制的应用开辟了更多可能性。
