Raabe Nils, Feng Tianli, Witting Tobias, Demircan Ayhan, Brée Carsten, Steinmeyer Günter
Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Straße 2a, 12489 Berlin, Germany.
Leibniz Universität Hannover, Welfengarten 1, 30167 Hannover, Germany.
Phys Rev Lett. 2017 Sep 22;119(12):123901. doi: 10.1103/PhysRevLett.119.123901. Epub 2017 Sep 18.
The concept of coherence is of fundamental importance for describing the physical characteristics of light and for evaluating the suitability for experimental application. In the case of pulsed laser sources, the pulse-to-pulse coherence is usually considered for a judgment of the compressibility of the pulse train. This type of coherence is often lost during propagation through a highly nonlinear medium, and pulses prove incompressible despite multioctave spectral coverage. Notwithstanding the apparent loss of interpulse coherence, however, supercontinua enable applications in precision frequency metrology that rely on coherence between different spectral components within a laser pulse. To judge the suitability of a light source for the latter application, we define an alternative criterion, which we term intrapulse coherence. This definition plays a limiting role in the carrier-envelope phase measurement and stabilization of ultrashort pulses. It is shown by numerical simulation and further corroborated by experimental data that filamentation-based supercontinuum generation may lead to a loss of intrapulse coherence despite near-perfect compressibility of the pulse train. This loss of coherence may severely limit active and passive carrier-envelope phase stabilization schemes and applications in optical high-field physics.
相干性概念对于描述光的物理特性以及评估实验应用的适用性至关重要。对于脉冲激光源，通常考虑脉冲间相干性来判断脉冲序列的可压缩性。这种相干性在通过高度非线性介质传播时常常会丧失，尽管脉冲具有多个倍频程的光谱覆盖范围，但脉冲却不可压缩。然而，尽管脉冲间相干性明显丧失，但超连续谱仍能实现依赖于激光脉冲内不同光谱成分之间相干性的精密频率计量应用。为了判断光源对于后一种应用的适用性，我们定义了一个替代标准，我们称之为脉冲内相干性。这个定义在超短脉冲的载波包络相位测量和稳定中起着限制作用。数值模拟表明并通过实验数据进一步证实，基于丝状化的超连续谱产生可能会导致脉冲内相干性丧失，尽管脉冲序列具有近乎完美的可压缩性。这种相干性的丧失可能会严重限制主动和被动载波包络相位稳定方案以及光学高场物理中的应用。
