Fabert Marc, Săpânțan Maria, Krupa Katarzyna, Tonello Alessandro, Leventoux Yann, Février Sébastien, Mansuryan Tigran, Niang Alioune, Wetzel Benjamin, Millot Guy, Wabnitz Stefan, Couderc Vincent
Université de Limoges, XLIM, UMR CNRS 7252, 123 Avenue A. Thomas, 87060, Limoges, France.
Institute of Physical Chemistry, Polish Academy of Sciences, ul. Kasprzaka 44/52, 01-224, Warsaw, Poland.
Sci Rep. 2020 Nov 24;10(1):20481. doi: 10.1038/s41598-020-77505-0.
A low intensity light beam emerges from a graded-index, highly multimode optical fibre with a speckled shape, while at higher intensity the Kerr nonlinearity may induce a spontaneous spatial self-cleaning of the beam. Here, we reveal that we can generate two self-cleaned beams with a mutual coherence large enough to produce a clear stable fringe pattern at the output of a nonlinear interferometer. The two beams are pumped by the same input laser, yet are self-cleaned into independent multimode fibres. We thus prove that the self-cleaning mechanism preserves the beams' mutual coherence via a noise-free parametric process. While directly related to the initial pump coherence, the emergence of nonlinear spatial coherence is achieved without additional noise, even for self-cleaning obtained on different modes, and in spite of the fibre structural disorder originating from intrinsic imperfections or external perturbations. Our discovery may impact theoretical approaches on wave condensation, and open new opportunities for coherent beam combining.
低强度光束从具有散斑形状的渐变折射率、高多模光纤中射出，而在较高强度下，克尔非线性可能会引发光束的自发空间自清洁。在此，我们揭示了我们能够生成两束自清洁光束，它们的相互相干性足够大，足以在非线性干涉仪的输出端产生清晰稳定的条纹图案。这两束光由同一输入激光泵浦，但被自清洁到独立的多模光纤中。因此，我们证明了自清洁机制通过无噪声的参量过程保持了光束的相互相干性。虽然与初始泵浦相干性直接相关，但即使是在不同模式上实现自清洁，并且尽管存在源于固有缺陷或外部扰动的光纤结构无序，非线性空间相干性的出现也是在没有额外噪声的情况下实现的。我们的发现可能会影响关于波凝聚的理论方法，并为相干光束合成开辟新的机会。
