偏离束腰入射对非局域非线性介质中高斯光束演化的影响

Influence of off-waist incidence on evolution of the Gaussian beam in the nonlocal nonlinear media

从 1 +1维强非局域模型出发 ,讨论了偏离束腰入射的高斯光束在非局域非线性介质中的传输特性 ,得到了精确的解析解 .结果表明 ,在聚焦介质中偏离束腰入射时 ,不论入射功率多大 ,光束束宽将发生周期性波动 ,光孤子不复存在 ,这与从高斯光束束腰入射的情况有本质的不同 ;入射功率决定了光束平均束宽的大小 ,入射位置决定了光束初始的演化趋势 .比较了在入射位置相同的条件下 ,聚焦介质、散焦介质和线性均匀介质中光束的演化 .给出了“空间啁啾”的定义 ,偏离束腰入射的物理本质是光束的不同入射位置对应不同的初始空间啁啾 .空间啁啾的概念 。

In this paper, we discuss the evolution of the off waist incident Gaussian beam in the nonlocal nonlinear media by use of the (1+1) dimensional strongly nonlocal model. An exact analytical solution for the evolution is obtained. We find that no matter how high the power of the incident beam is, the beam width will oscillate periodically and no spatial soliton will exist, which is substantially different from the on waist incident case. The influence of the input power and incident position on beam evolution is also discussed. The higher the input power, the narrower the beam width is. The incident position determines the initial evolution trend. The definition of a “spatial chirp” is given, to our knowledge, for the first time. The physical origin of the above phenomenon is that the different incident position corresponds to the different spatial chirp. The concept of the spatial chirp provides a new physical qualitative insight into the evolution of optical beams. The comparisons of beam evolutions in focusing media, in defocusing media and in linear homogeneous media are also given.