Rudenkov Alexander, Kalashnikov Vladimir L, Demesh Maksim, Tolstik Nikolai, Sorokin Evgeni, Sorokina Irina T
Opt Express. 2025 Jul 14;33(14):28935-28946. doi: 10.1364/OE.558940.
We introduce the first ultrafast Cr:ZnS amplifier in a 34-mm-long depressed-cladding waveguide with a cross-section of up to 50 m and an excellent output beam quality of M ∼ 1.2. In a chirped pulse amplification scheme incorporating a Chirped Volume Bragg Grating stretcher/compressor, the amplifier achieves an optical gain of 75 over 15 mm, corresponding to a 12 dB/cm gain coefficient. The amplifier delivers 2.35 W of average output power in a single pass, with the amplified pulses being compressed to 235 fs. Furthermore, our numerical 3D model, which accounts for the spatial profiles of both the pump and the seed beams, reveals and describes experimental observation of what we believe to be a novel phenomenon: multimode relaxation to the fundamental transverse mode in a large-mode-area (LMA) waveguide, occurring without degradation of the effective mode volume or amplification efficiency. We also demonstrate that without stretching, the waveguided propagation in a non-centrosymmetric Cr:ZnS medium enables effective generation of multiple harmonics even for the relatively long 100-fs seed pulses, making an integrated carrier-envelope phase stabilization using 2f-3f or 3f-4f schemes within reach.
我们介绍了首个超快Cr:ZnS放大器，它采用了长34毫米的下陷包层波导，其横截面高达50微米，输出光束质量优异，M约为1.2。在结合啁啾体布拉格光栅展宽器/压缩器的啁啾脉冲放大方案中，该放大器在15毫米的长度上实现了75的光学增益，对应增益系数为12分贝/厘米。该放大器单次通过可输出2.35瓦的平均输出功率，放大后的脉冲被压缩至235飞秒。此外，我们的三维数值模型考虑了泵浦光束和种子光束的空间分布，揭示并描述了我们认为是一种新现象的实验观察结果：在大模面积（LMA）波导中多模弛豫到基横模，且有效模体积或放大效率没有下降。我们还证明，在不展宽的情况下，在非中心对称的Cr:ZnS介质中的波导传播即使对于相对较长的100飞秒种子脉冲也能有效产生多个谐波，使得使用2f - 3f或3f - 4f方案实现集成载波包络相位稳定成为可能。
