Heidt Alexander M, Modupeh Hodasi Joanna, Rampur Anupamaa, Spangenberg Dirk-Mathys, Ryser Manuel, Klimczak Mariusz, Feurer Thomas
Institute of Applied Physics, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland.
Department of Physics, University of Ghana, Legon, Accra, Ghana.
Sci Rep. 2020 Oct 7;10(1):16734. doi: 10.1038/s41598-020-73753-2.
We report a low noise, broadband, ultrafast Thulium/Holmium co-doped all-fiber chirped pulse amplifier, seeded by an Erbium-fiber system spectrally broadened via coherent supercontinuum generation in an all-normal dispersion photonic crystal fiber. The amplifier supports a - 20 dB bandwidth of more than 300 nm and delivers high quality 66 fs pulses with more than 70 kW peak power directly from the output fiber. The total relative intensity noise (RIN) integrated from 10 Hz to 20 MHz is 0.07%, which to our knowledge is the lowest reported RIN for wideband ultrafast amplifiers operating at 2 µm to date. This is achieved by eliminating noise-sensitive anomalous dispersion nonlinear dynamics from the spectral broadening stage. In addition, we identify the origin of the remaining excess RIN as polarization modulational instability (PMI), and propose a route towards complete elimination of this excess noise. Hence, our work paves the way for a next generation of ultra-low noise frequency combs and ultrashort pulse sources in the 2 µm spectral region that rival or even outperform the excellent noise characteristics of Erbium-fiber technology.
我们报道了一种低噪声、宽带、超快的铥/钬共掺杂全光纤啁啾脉冲放大器，其种子源是一个通过全正色散光子晶体光纤中的相干超连续谱产生而实现光谱展宽的铒光纤系统。该放大器支持超过300 nm的 - 20 dB带宽，并直接从输出光纤输出高质量的66 fs脉冲，峰值功率超过70 kW。从10 Hz到20 MHz积分的总相对强度噪声（RIN）为0.07%，据我们所知，这是迄今为止报道的在2 µm波长工作的宽带超快放大器中最低的RIN。这是通过在光谱展宽阶段消除对噪声敏感的反常色散非线性动力学来实现的。此外，我们确定了剩余过量RIN的来源是偏振调制不稳定性（PMI），并提出了一条完全消除这种过量噪声的途径。因此，我们的工作为2 µm光谱区域的下一代超低噪声频率梳和超短脉冲源铺平了道路，这些源可与铒光纤技术的优异噪声特性相媲美甚至超越。
