We have developed a numerical framework that allows estimation of coherence in spatiotemporal and spatiospectral domains. Correlation properties of supercontinuum (SC) pulses generated in a bulk medium are investigated by means of second-order coherence theory of non-stationary fields. The analysis is based on simulations of individual space–time and space–frequency realizations of pulses emerging from a 5 mm thick sapphire plate, in the regimes of normal, zero, and anomalous group velocity dispersion. The temporal and spectral coherence properties are analyzed in the near field (as a function of spatial position at the exit plane of the nonlinear medium) and as a function of propagation direction (spatial frequency) in the far field. Unlike in fiber-generated SC, the bulk case features spectacularly high degrees of temporal and spectral coherence in both the spatial and spatial-frequency domains, with increasing degrees of coherence at higher pump energies. When operating near the SC generation threshold, the overall degrees of temporal and spectral coherence exhibit an axial dip in the spatial domain, whereas in the far field, the degree of coherence is highest around the optical axis.

中文翻译：

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体生成超连续谱的相干性

我们开发了一个数值框架，可以估计时空和时空域的相干性。通过非平稳场的二阶相干理论研究了在体介质中产生的超连续谱 (SC) 脉冲的相关特性。该分析基于在正常、零和异常群速度色散状态下对从 5 毫米厚的蓝宝石板上发出的脉冲的单个时空和空间频率实现的模拟。在近场（作为非线性介质出射平面的空间位置的函数）和远场中作为传播方向（空间频率）的函数分析时间和光谱相干特性。与纤维生成的 SC 不同，大块案例在空间和空间频率域都具有非常高的时间和光谱相干性，随着泵浦能量的增加，相干性程度增加。当在 SC 生成阈值附近运行时，时间和光谱相干的整体程度在空间域中呈现轴向倾斜，而在远场中，光轴周围的相干程度最高。