Preparation, control, and measurement of optical vortices are increasingly important, as they play essential roles in both fundamental science and optical technology applications. Spatial light modulation is the main approach behind the control strategies, although there are limitations concerning the controllable wavelength. It is therefore crucial to develop approaches that expand the spectral range of light modulation. Here, we demonstrate the modulation of light by light in nonlinear optical interactions to demonstrate the identification of the topological charge of optical vortices. A triangular-lattice pattern is observed in light beams resulting from the spatial cross modulation between an optical vortex and a triangular shaped beam undergoing parametric interaction. Both up- and downconversion processes are investigated, and the far-field image of the converted beam exhibits a triangular lattice. The number of sites and the lattice orientation are determined by the topological charge of the vortex beam. In the downconversion process, the lattice orientation can also be affected by phase conjugation. The observed cross modulation works for a large variety of spatial field structures. Our results show that modulation of light by light can be used at wavelengths for which solid-state devices are not yet available.

中文翻译：

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光学涡旋非线性波混频中三角格图案的观察

光学涡旋的制备、控制和测量变得越来越重要，因为它们在基础科学和光学技术应用中都发挥着重要作用。空间光调制是控制策略背后的主要方法，尽管在可控波长方面存在限制。因此，开发扩大光调制光谱范围的方法至关重要。在这里，我们展示了非线性光学相互作用中光对光的调制，以证明光学涡旋拓扑电荷的识别。在由光学涡旋和经历参量相互作用的三角形光束之间的空间交叉调制产生的光束中观察到三角形晶格图案。研究了上变频和下变频过程，转换光束的远场图像呈现出三角形晶格。位点的数量和晶格取向由涡旋光束的拓扑电荷决定。在下转换过程中，晶格取向也会受到相位共轭的影响。观察到的交叉调制适用于多种空间场结构。我们的结果表明，光调制光可用于固态器件尚不可用的波长。