Two-photon fluorescence (TPF) ellipsoid formed by a focused femtosecond laser into luminescent media serves as a fundamental pixel for TPF spatiotemporal imaging. Visualizing spatiotemporal evolution of the TPF ellipsoid itself in a selected luminescent medium is important for correctly reconstructing and interpreting spatiotemporal information of imaged targets. Here, we report a new spatiotemporal sectioning technique with a luminescent CsPbBr₃ nanosheet and visualize the spatiotemporal evolution of TPF ellipsoid along the axial direction. Time-resolved axial lengths of TPF ellipsoids turn out to broaden nonlinearly with a turning point at about 600 ps. By comparison experiments, observed phenomena are attributed to photocarrier trapping and TPF photon recycling processes within CsPbBr₃ nanosheets. The spatiotemporal sectioning technique is expected to be widely applicable, which will ignite a plethora of investigations and applications utilizing TPF ellipsoid.

双光子荧光 (TPF) 椭球体由聚焦飞秒激光形成到发光介质中，作为 TPF 时空成像的基本像素。在选定的发光介质中可视化 TPF 椭球本身的时空演化对于正确重建和解释成像目标的时空信息非常重要。在这里，我们报告了一种具有发光 CsPbBr ₃纳米片的新时空切片技术，并可视化了 TPF 椭球沿轴向的时空演化。TPF 椭球的时间分辨轴向长度结果显示为非线性加宽，转折点约为 600 ps。通过对比实验，观察到的现象归因于 CsPbBr ₃内的光载流子捕获和 TPF 光子回收过程纳米片。时空切片技术有望得到广泛应用，这将引发大量利用 TPF 椭球的研究和应用。