LiNbO₃晶体中非相干空间亮孤子的动态演化特性

Dynamics Evolution Characteristic of Incoherent Bright Spatial Solitons in LiNbO₃ Crystal

摘要: 本文理论研究了自散焦LiNbO₃晶体中非相干亮光伏孤子的形成机理及其动态演化特性。研究发现，通过加载背景光的方法能够实现LiNbO₃晶体由自散焦向自聚焦的转换并形成亮空间孤子。以LiNbO₃晶体为例，给出了折射率空间分布与光伏常数比K 之间的关系，给出了亮光伏孤子的存在曲线。进一步采用相干密度法理论分析了非相干亮光伏孤子在LiNbO₃晶体中的传输特性，并利用分步傅里叶算法数值模拟了K 值对孤子形成的影响。此外，非相干亮光伏孤子的形成还受强度比值 r _T 和光源角功率谱宽度θ₀ 的影响。通过加载背景光的方法可以实现无偏压条件下亮暗孤子的切换，这对基于孤子的全光器件研究提供可靠性参考。

Abstract: We theoretically study the formation mechanism and dynamic evolution characteristics of inco-herent bright photovoltaic (PV) solitons in self-defocusing LiNbO₃ crystal. It is found that the transition of self-defocusing to self-focusing can be realized by adding a background beam in LiNbO₃ crystal, and bright spatial solitons generate under suitable conditions. Taking LiNbO₃ as an example, we give the relationship between the spatial distribution of refractive index and the ratio of PV constant K . We then calculate the existence curve of bright PV solitons. Furthermore, we analyze the propagation characteristics of incoherent bright PV solitons using coherent density approach, and simulate how the soliton formation is influenced by K values with split-step Fourier method. The bright incoherent PV solitons are affected by intensity ratios r _T and the width of source angular power spectrum θ₀ . It realizes the switching of bright and dark solitons by adding a background beam without extra bias voltage, which provides useful reference for all optical devices design based on solitons.