Schaarschmidt Kay, Kobelke Jens, Nolte Stefan, Meyer Tobias, Schmidt Markus A
Opt Express. 2020 Aug 17;28(17):25037-25047. doi: 10.1364/OE.399771.
Third harmonic generation in a circular liquid core step-index fiber filled with a highly transparent inorganic solvent is demonstrated experimentally using ultrafast pump pulses of different durations in the telecom domain for the first time. Specifically we achieve intermodal phase matching to the HE higher order mode at the harmonic wavelength and found clear indications of a non-instantaneous molecular contribution to the total nonlinearity in the spectral broadening of the pump. Spectral power evolution and efficiency of the conversion process is studied for all pulse parameters, while we found the greatest photon yield for the longest pulses as well as an unexpected blue-shift of the third harmonic wavelength with increasing pump power. Our results provide the basis for future studies aiming at using this tunable fiber platform with a sophisticated nonlinear response in the context of harmonic generation.
首次通过实验证明，在填充高透明无机溶剂的圆形液芯阶跃折射率光纤中，利用电信领域不同持续时间的超快泵浦脉冲可产生三次谐波。具体而言，我们在谐波波长处实现了与HE高阶模式的模间相位匹配，并在泵浦光谱展宽中发现了分子对总非线性有非瞬时贡献的明确迹象。针对所有脉冲参数研究了转换过程的光谱功率演变和效率，同时我们发现最长脉冲的光子产率最高，并且三次谐波波长随着泵浦功率的增加出现了意外的蓝移。我们的结果为未来旨在利用这种具有复杂非线性响应的可调谐光纤平台进行谐波产生的研究提供了基础。
