Twist phase is a nontrivial second-order phase that only exists in a partially coherent field, providing a new degree of freedom for manipulating statistical properties of random light. However, in the existing experimental methods either it is difficult to control the twist phase or requires a large number of pseudo/random modes to approximately synthesize the twisted beams. In this work, we demonstrate a simple and efficient approach, based on the superposition of mutually orthogonal Laguerre-Gaussian modes with appropriate mode weights, to generate the twisted beams with a controllable twist phase. We show that a smaller number of modes are required to synthesize the twisted beams, compared to the pseudo-mode superposition, because the orthogonal coherent modes are used in the present method. We experimentally generate the twisted Gaussian Schell-model beams with controllable strength of twist phase and measure their degree of coherence and average intensity behavior during propagation. The experimental results agree well with the theoretical predictions. Our approach will promote the application of the twisted partially coherent beams in optical imaging and free-space optical communications.

中文翻译：

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生成具有相干模式叠加的扭曲高斯 Schell 模型光束

扭曲相位是一种非平凡的二阶相位，仅存在于部分相干场中，为操纵随机光的统计特性提供了新的自由度。然而，现有的实验方法要么难以控制扭曲相位，要么需要大量的伪/随机模式来近似合成扭曲光束。在这项工作中，我们展示了一种简单有效的方法，基于具有适当模式权重的相互正交的拉盖尔-高斯模式的叠加，以生成具有可控扭曲相位的扭曲光束。我们表明，与伪模式叠加相比，合成扭曲光束所需的模式数量更少，因为本方法中使用了正交相干模式。我们通过实验生成具有可控扭曲相位强度的扭曲高斯 Schell 模型光束，并测量它们在传播过程中的相干度和平均强度行为。实验结果与理论预测非常吻合。我们的方法将促进扭曲部分相干光束在光学成像和自由空间光通信中的应用。