Jafari Rana, Jones Travis, Trebino Rick
Opt Express. 2019 Feb 4;27(3):2112-2124. doi: 10.1364/OE.27.002112.
We demonstrate a novel algorithmic approach for the second-harmonic-generation (SHG) frequency-resolved optical gating (FROG) ultrashort-pulse-measurement technique that always converges and, for complex pulses, is also much faster. It takes advantage of the Paley-Wiener Theorem to retrieve the precise pulse spectrum-half the desired information-directly from the measured trace. It also uses a multi-grid approach, permitting the algorithm to operate on smaller arrays for early iterations and on the complete array for only the final few iterations. We tested this approach on more than 25,000 randomly generated complex pulses with time-bandwidth products up to 100, yielding SHG FROG traces to which noise was added, and have achieved convergence to the correct pulse in all cases. Moreover, convergence occurs in less than half the time for extremely large traces corresponding to extremely complex pulses.
我们展示了一种用于二次谐波产生（SHG）频率分辨光学门控（FROG）超短脉冲测量技术的新型算法方法，该方法总能收敛，并且对于复杂脉冲而言速度也快得多。它利用帕利 - 维纳定理直接从测量迹线中检索精确的脉冲频谱——即所需信息的一半。它还采用了多重网格方法，允许算法在早期迭代时在较小数组上运行，而仅在最后几次迭代时在完整数组上运行。我们在超过25000个随机生成的、时间带宽积高达100的复杂脉冲上测试了这种方法，生成了添加了噪声的SHG FROG迹线，并且在所有情况下都实现了收敛到正确的脉冲。此外，对于对应于极其复杂脉冲的极大迹线，收敛时间不到一半。
