Sun Can, Barsi Christopher, Fleischer Jason W
Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA.
Opt Express. 2008 Dec 8;16(25):20676-86. doi: 10.1364/oe.16.020676.
We study the over-focusing of spatial light beams due to self-focusing nonlinearity, in both local and nonlocal nonlinear media. Numerical simulation of both cases reveals a peaked profile, with a near-cusp at the center surrounded by exponentially-decaying tails, at a critical self-focusing power. The profile is a local effect, occurring as diffraction counteracts nonlinearity. Nonlocality, however, is needed to prevent modulation instability of the initial beam and to prevent catastrophic collapse in 2D. The peaked profile remains for weak nonlocality but disappears for wide nonlocal responses. Beyond the critical power for a peaked solution, or for longer propagation distances, competition between nonlinearity and diffraction causes oscillatory collapse-bounce behavior. The numerical results are confirmed by observing these dynamics in a self-focusing glass with a nonlocal, thermal response.
我们研究了在局部和非局部非线性介质中，由于自聚焦非线性导致的空间光束过度聚焦现象。对这两种情况的数值模拟均显示，在临界自聚焦功率下，光束轮廓呈峰值状，中心处有近尖点，周围是指数衰减的尾部。这种轮廓是一种局部效应，是由衍射与非线性相互作用产生的。然而，需要非局部性来防止初始光束的调制不稳定性，并防止二维空间中的灾难性坍缩。对于弱非局部性，峰值轮廓仍然存在，但对于宽非局部响应，该轮廓消失。超过峰值解的临界功率或更长的传播距离时，非线性与衍射之间的竞争会导致振荡坍缩-反弹行为。通过在具有非局部热响应的自聚焦玻璃中观察这些动力学，证实了数值结果。
