Fellinger Jakob, Mayer Aline S, Winkler Georg, Grosinger Wilfrid, Truong Gar-Wing, Droste Stefan, Li Chen, Heyl Christoph M, Hartl Ingmar, Heckl Oliver H
Opt Express. 2019 Sep 30;27(20):28062-28074. doi: 10.1364/OE.27.028062.
We demonstrate dual-comb generation from an all-polarization-maintaining dual-color ytterbium (Yb) fiber laser. Two pulse trains with center wavelengths at 1030 nm and 1060 nm respectively are generated within the same laser cavity with a repetition rate around 77 MHz. Dual-color operation is induced using a tunable mechanical spectral filter, which cuts the gain spectrum into two spectral regions that can be independently mode-locked. Spectral overlap of the two pulse trains is achieved outside the laser cavity by amplifying the 1030-nm pulses and broadening them in a nonlinear fiber. Spatially overlapping the two arms on a simple photodiode then generates a down-converted radio frequency comb. The difference in repetition rates between the two pulse trains and hence the line spacing of the down-converted comb can easily be tuned in this setup. This feature allows for a flexible adjustment of the tradeoff between non-aliasing bandwidth vs. measurement time in spectroscopy applications. Furthermore, we show that by fine-tuning the center-wavelengths of the two pulse trains, we are able to shift the down-converted frequency comb along the radio-frequency axis. The usability of this dual-comb setup is demonstrated by measuring the transmission of two different etalons while the laser is completely free-running.
我们展示了全保偏双色镱（Yb）光纤激光器中的双梳状频谱产生。在同一个激光腔内产生了分别具有1030纳米和1060纳米中心波长的两个脉冲序列，重复频率约为77兆赫兹。使用可调谐机械光谱滤波器实现双色运转，该滤波器将增益谱切割成两个可独立锁模的光谱区域。通过在非线性光纤中放大1030纳米脉冲并展宽它们，在激光腔外实现了两个脉冲序列的光谱重叠。然后在一个简单的光电二极管上使两个臂在空间上重叠，产生一个下变频射频梳状频谱。在此设置中，可以轻松调节两个脉冲序列之间的重复频率差异，从而调节下变频梳状频谱的线间距。这一特性允许在光谱应用中灵活调整非混叠带宽与测量时间之间的权衡。此外，我们表明，通过微调两个脉冲序列的中心波长，能够使下变频频率梳状频谱沿射频轴移动。在激光器完全自由运转的情况下，通过测量两个不同标准具的透射率，证明了这种双梳状频谱设置的实用性。
