Picozzi Antonio, Aschieri Pierre
CNRS-LPMC, Université de Nice Sophia-Antipolis, Nice, France and Laboratoire de Physique de l'Université de Bourgogne, CNRS, Dijon, France.
Phys Rev E Stat Nonlin Soft Matter Phys. 2005 Oct;72(4 Pt 2):046606. doi: 10.1103/PhysRevE.72.046606. Epub 2005 Oct 13.
We study the influence of group-velocity dispersion (or diffraction) on the coherence properties of the parametric three-wave interaction driven from an incoherent pump wave. We show that, under certain conditions, the incoherent pump may efficiently amplify a signal wave with a high degree of coherence, in contrast with the usual kinetic description of the incoherent three-wave interaction. The group-velocity dispersion is shown to be responsible for a spectral filtering process, in which the coherence of the generated signal increases, as the coherence of the pump wave decreases. As a result, the coherence acquired by the signal in the presence of an incoherent pump, is higher than that acquired in the presence of a fully coherent pump. The mechanism underlying this intriguing result is based on the emergence of a mutual coherence between the incoherent pump and the generated idler wave. We calculate explicitly the degree of mutual coherence between the pump and idler waves and show that the two incoherent waves become completely correlated in the full incoherent regime of interaction. The theory is in quantitative agreement with the numerical simulations. To motivate the experimental confirmation of our theory, we characterize the dispersion properties of an actual quadratic nonlinear optical crystal in which the process of signal coherence enhancement induced by pump incoherence may be studied experimentally.
我们研究了群速度色散（或衍射）对由非相干泵浦波驱动的参量三波相互作用的相干特性的影响。我们表明，在某些条件下，与非相干三波相互作用的通常动力学描述相反，非相干泵浦可以有效地放大具有高度相干性的信号波。群速度色散被证明是一个光谱滤波过程的原因，在这个过程中，随着泵浦波相干性的降低，所产生信号的相干性增加。结果，在存在非相干泵浦时信号获得的相干性高于在存在完全相干泵浦时获得的相干性。这一有趣结果背后的机制基于非相干泵浦与所产生的闲频波之间出现的相互相干性。我们明确计算了泵浦波和闲频波之间的相互相干程度，并表明在完全非相干相互作用 regime 中，这两个非相干波变得完全相关。该理论与数值模拟在定量上一致。为了推动对我们理论的实验验证，我们表征了一种实际二次非线性光学晶体的色散特性，在其中可以通过实验研究由泵浦非相干性引起的信号相干增强过程。
