Liao Ruoyu, Tian Haochen, Feng Tianli, Song Youjian, Hu Minglie, Steinmeyer Günter
Opt Lett. 2019 Feb 15;44(4):1060-1063. doi: 10.1364/OL.44.001060.
The f-to-2f interferometer plays a key role for carrier-envelope phase (CEP) measurement and subsequent stabilization. The CEP measurement typically relies on the application of two optical nonlinearities, namely supercontinuum generation and second-harmonic generation. Then the cascadation of these nonlinearities often leads to signal levels on the order of a few photons per pulse. We experimentally demonstrate that the introduction of optical gain into the infrared arm of an f-to-2f interferometer can mitigate this detection bottleneck and improve signal-to-noise ratios by 20 dB compared to purely passive schemes. We further show that this measure allows for residual phase jitters between the carrier and envelope of about 10 mrad, corresponding to record-breaking timing jitters in the single attosecond regime. Moreover, the method appears generally applicable to a wide range of oscillators in the near-infrared and may enable stable CEP locking of mode-locked oscillators that so far have resisted stabilization. Finally, we propose a parametric variant of the active f-to-2f interferometer that can be used for laser amplifiers with kilohertz repetition rates and below.
f - 2f干涉仪在载波包络相位（CEP）测量及后续稳定过程中起着关键作用。CEP测量通常依赖于两种光学非线性效应的应用，即超连续谱产生和二次谐波产生。这些非线性效应的级联往往会导致每个脉冲的信号水平达到几个光子的量级。我们通过实验证明，在f - 2f干涉仪的红外臂中引入光学增益可以缓解这一检测瓶颈，并且与纯被动方案相比，能将信噪比提高20分贝。我们进一步表明，这一措施能使载波和包络之间的残余相位抖动约为10毫弧度，这对应于单阿秒 regime中破纪录的定时抖动。此外，该方法似乎普遍适用于近红外范围内的各种振荡器，并且可能实现迄今为止难以实现稳定的锁模振荡器的稳定CEP锁定。最后，我们提出了一种有源f - 2f干涉仪的参数变体，可用于重复频率为千赫兹及以下的激光放大器。
