Frequency-resolved optical gating (FROG) is a popular technique for characterizing ultrashort laser pulses. This technique comprises two steps. First, a spectrogram, named FROG trace, is constructed for a pulse by measuring process. Second, an efficient algorithm is employed to retrieve the pulse information from its FROG trace. By expressing an arbitrary FROG trace using matrix multiplication, we confirm that the data on all the complex spectral components constituting the relative pulse are, in principle, encoded in the value of each point of the trace. Considering this fact and the characteristics of the measuring devices, flexibly shaped FROG traces are built by simultaneously applying low-pass filtering and up-sampling along the frequency axis and down-sampling along the delay axis to the conventional square ones. Furthermore, these practical traces can be used for the effective reconstruction of ultrashort laser pulses via the ptychography algorithm. Utilizing this specially designed trace will significantly reduce the difficulty and time-consumption in the first step of the FROG process.

频率分辨光学选通（FROG）是表征超短激光脉冲的流行技术。该技术包括两个步骤。首先，通过测量过程为脉冲构造一个称为FROG迹线的频谱图。其次，采用一种有效的算法从其FROG迹线中检索脉冲信息。通过使用矩阵乘法表示任意FROG迹线，我们可以确认，构成相对脉冲的所有复杂频谱分量的数据原则上都编码在迹线每个点的值中。考虑到这一事实和测量设备的特性，通过同时沿频率轴应用低通滤波和上采样以及沿延迟轴的下采样到常规平方信号来构建灵活成形的FROG迹线。此外，这些实际的痕迹可以通过声谱算法用于超短激光脉冲的有效重建。利用这种特殊设计的迹线将大大减少FROG流程第一步中的难度和时间消耗。