AI 中文总结
研究二次谐波产生中光源非相干性影响，推导并验证二次谐波频率下远场相干函数解析表达式，结果表明其相干性随光在非线性晶体内传播而增加，将非线性确立为光学相干自由度，开辟新研究方向。
AI 中文摘要
非线性光学相互作用通常由相干光源驱动。然而，最近非相干光源在非线性光学中也展现出新机遇。本文研究了二次谐波产生中光源非相干性的影响。我们推导并通过实验验证了二次谐波频率下远场相干函数的解析表达式，这是著名的范西特 - 泽尔尼克定理的推广。与线性光学情况不同，这里的结果不仅取决于光源空间分布，还取决于晶体的非线性结构。通过杨氏双缝测量进一步表明，二次谐波处的相干性随着光在非线性晶体内传播而增加。我们的结果将非线性确立为光学相干的一个自由度，在统计光学和非线性光学的交叉领域开辟了新的研究方向。
英文摘要
Nonlinear optical interactions are typically driven by coherent sources. Recently, however, incoherent sources have also been shown to offer new opportunities in nonlinear optics. Here we study the effects of the source incoherence in second harmonic generation. We derive and experimentally validate an analytic expression for the far-field coherence function at the second harmonic frequency, which is a generalization of the well-known van Cittert-Zernike theorem. Unlike the linear optics case, here the results depend not only on the source spatial distribution, but also on the nonlinear structure of the crystal. We further show, by performing Young's double-slit measurement, that the coherence at the second harmonic increases as the light propagates inside the nonlinear crystal. Our results establish nonlinearity as a degree of freedom for optical coherence, opening a new research area at the interface of statistical optics and nonlinear optics.
Comments8 pages, 5 figures
