Rampur Anupamaa, Spangenberg Dirk-Mathys, Stępniewski Grzegorz, Dobrakowski Dominik, Tarnowski Karol, Stefańska Karolina, Paździor Adam, Mergo Paweł, Martynkien Tadeusz, Feurer Thomas, Klimczak Mariusz, Heidt Alexander M
Opt Express. 2020 May 25;28(11):16579-16593. doi: 10.1364/OE.392871.
We experimentally investigate the spectro-temporal characteristics of coherent supercontinuum (SC) pulses generated in several implementations of silica and soft-glass all-normal dispersion (ANDi) photonic crystal fibers optimized for pumping with Erbium (Er):fiber femtosecond laser technology. We characterize the resulting SC using time-domain ptychography, which is especially suitable for the measurement of complex, spectrally broadband ultrashort pulses. The measurements of the ANDi SC pulses reveal intricate pulse shapes, considerable temporal fine structure, and oscillations on time scales of < 25 femtoseconds, which differ from the smoothness and simplicity of temporal profiles obtained in numerical simulations and observed in previous experiments. We link the measured complex features to temporal sub-structures of the pump pulse, such as pre- and post-pulses and low-level pedestals, which are common in high pulse energy ultrafast Er:fiber systems. We also observe spectro-temporal structures consistent with incoherent noise amplification in weakly birefringent fiber samples. Our results highlight the importance of the pump source and polarization-maintaining (PM) fibers for high-quality SC generation and have practical relevance for many ultrafast photonics applications employing ANDi fiber-based SC sources.
我们通过实验研究了在几种为用铒（Er）：光纤飞秒激光技术泵浦而优化的二氧化硅和软玻璃全正色散（ANDi）光子晶体光纤中产生的相干超连续谱（SC）脉冲的光谱-时间特性。我们使用时域叠层成像技术对产生的超连续谱进行表征，该技术特别适用于测量复杂的、光谱宽带的超短脉冲。对ANDi超连续谱脉冲的测量揭示了复杂的脉冲形状、相当可观的时间精细结构以及在小于25飞秒时间尺度上的振荡，这与数值模拟中获得的时间轮廓的平滑性和简单性以及先前实验中观察到的情况不同。我们将测量到的复杂特征与泵浦脉冲的时间子结构联系起来，例如前脉冲和后脉冲以及低电平基座，这些在高脉冲能量超快Er：光纤系统中很常见。我们还观察到与弱双折射光纤样品中非相干噪声放大一致的光谱-时间结构。我们的结果突出了泵浦源和保偏（PM）光纤对于高质量超连续谱产生的重要性，并且对于许多采用基于ANDi光纤的超连续谱源的超快光子学应用具有实际意义。
