扭曲高斯谢尔模型光束的反常二次谐波产生
Anomalous Second Harmonic Generation of Twisted Gaussian Schell Model Beams
AI总结：
本研究通过理论与实验探究扭曲高斯谢尔模型光束的二次谐波产生，发现两种合成方法下输出光束特性不同，一种仍为TGSM光束，另一种呈带凹陷的反常交叉谱密度，且凹陷深度与扭曲相位参数相关。
摘要：
我们从理论和实验上研究了以扭曲高斯谢尔模型（twisted Gaussian Schell model, TGSM）光束为基频场的光学二次谐波产生（second harmonic generation, SHG）。我们采用II类相位匹配，分析了当输入基频光具备TGSM结构时，SHG输出光束的交叉谱密度（cross spectral density, CSD）。我们分析了两种制备TGSM基频光束的合成方法，发现其中一种方法产生的SHG仍为TGSM光束；另一种方法产生的SHG并非TGSM光束，且呈现反常的交叉谱密度，其横向空间结构中存在凹陷而非峰值。此外，我们证明该凹陷深度与扭曲相位参数直接相关，无扭曲的GSM光束不存在此凹陷。我们的结果表明，基频TGSM光束产生的SHG既可以是倍频TGSM光束，也可以是非TGSM光束，具体取决于合成方法。
英文摘要：
We investigate theoretically and experimentally the optical second harmonic generation (SHG) with a twisted Gaussian Schell model (TGSM) beam as the fundamental field. We use Type-II phase matching and analyze the cross spectral density (CSD) of the SHG output beam when the input fundamental is prepared with a TGSM structure. We analyze two synthetization methods for preparing the TGSM fundamental beam and we find that for one method the SHG is also a TGSM beam. For the other method, we find that the SHG is not a TGSM beam and presents an anomalous CSD possessing a dip instead of a peak in the transverse spatial structure. Moreover, we show that the dip depth is directly related to the twisted phase parameter, being absent for a non twisted GSM beam. Our results show that the SHG from a fundamental TGSM beam can result in a doubled frequency TGSM or in a non-TGSM beam depending on the synthetization method.
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