共查询到19条相似文献,搜索用时 160 毫秒
1.
按照单轴晶体光束传输理论,求得了具有交叉相位艾里-厄米-高斯光束(AiHGB)在单轴晶体中传输时的解析表达式.数值模拟计算结果表明,具有初始交叉相位的AiHGB在晶体中传输时仍是线偏振的,但不一定是传输不变的.具体地讲,有赖于交叉相位系数、光束参数及晶体材料参数,初始交叉相位会引起AiHGB光斑连续转动,在从近场到远场的整个传输过程中总的转动角是90°.并且交叉相位系数足够大时,AiHGB光斑只有纯转动;而交叉相位系数适当小时,AiHGB光斑除了取向转动还有光斑形状变化.这些结果表明通过恰当选择晶体材料(即折射率)和附加交叉相位因子的系数,可以精准调控光束花样形状的取向与结构,也可用于确定晶体材料折射率或测定交叉相位因子的系数. 相似文献
2.
为了研究光束在梯度折射率介质中的传输规律,利用广义惠更斯-菲涅耳衍射积分法,推导出余弦高斯光束在梯度折射率介质中传输的解析表达式,对余弦高斯光束在梯度折射率介质中的传输特性进行了分析,并进一步讨论了介质梯度折射率系数和调制参数对传输特性的影响。结果表明,余弦高斯光束在梯度折射率介质中传输时,轴上光强分布呈现周期性变化,横向光强分布受梯度折射率系数和调制参数影响较大。余弦高斯光束传输时具有不稳定性,通过适当调节参数,可在空间某位置实现余弦高斯光束的整形。 相似文献
3.
本文基于光波在宇称时间对称波导中传输的理论模型,数值研究各阶亮孤子在罗森莫尔斯势宇称时间对称波导中的传输特性。宇称时间对称波导的折射率分布对光具有线性聚焦作用,而增益/损耗分布可以引起光束能量的横向流动。研究结果表明:当折射率调制深度为正时,一阶亮孤子在该波导中传输形成波浪形光束。当折射率调制深度为负时,一阶亮孤子分裂形成两束光,一束光发生弥散,另一束光以一定的速度向前传输,而增益/损耗调制深度会影响分裂后光束的传输行为;二阶亮孤子在较低的增益/损耗调制深度下传输形成稳定的呼吸光束;三阶亮孤子在传输过程中出现光波周期分裂与会聚现象;四阶及其以上高阶亮孤子在该波导中都不能稳定传输。此研究结果可为宇称时间对称在光波导中的应用提供一定的理论依据。 相似文献
4.
分析了大气湍流对采用多抖动法实现的相干合成阵列光束中相位调制信号的影响. 文章首先根据广义惠更斯-菲涅耳原理,采用折射率结构函数对大气湍流进行描述,推导了多抖动法相干合成中阵列光束通过大气湍流后相位调制信号的一般表达式. 在此基础上进行数值模拟,分析了传输距离、湍流强度、光束阵列占空比和光斑尺寸等因素对相位调制信号的影响. 研究发现随着传输距离的增大,相位调制信号强度会先增大后减小,存在一个极大值点;随着湍流强度的增强,相位调制信号强度极大值点的出现距离不断缩短;当光束阵列占空比一定时,随着光斑尺寸的增大
关键词:
大气湍流
相干合成
多抖动法
相位调制 相似文献
5.
6.
利用单轴晶体光束传输理论,求得了具有附加球面相位Airy光束在单轴晶体中的传输公式.数值模拟计算结果表明,线偏振附加球面相位Airy光束在晶体中传输时仍为线偏振,但不是传输不变的.粗略地讲,具有附加球面相位的Airy光束在晶体中传输时,近场是传输不变的;而在由晶体寻常与非寻常折射率和球面半径共同确定的两个特定传输距离处,传输光束转换成了取向不同的Gaussian-Airy光束,且高斯依赖的束宽度敏感地与截断因子相关;而当光束依次穿过此两位置时光斑花样先后相对于两横向轴平面做镜像演化,且镜像演化顺序也与晶体寻常和非寻常折射率相对大小密切相关,其总的效果是远场强度花样能恢复原样但花样取向产生了关于对过横平面二、四象限平分平面的镜像演化.这些结果表明,通过恰当选择晶体材料(即折射率)和附加球面相位的半径R,可以调控光束花样的形状、取向及表征各向异性材料的相关性质. 相似文献
7.
8.
9.
10.
采用磁性电磁超构材料,设计了具有柱对称梯度折射率分布的二维体系,根据梯度的不同可以实现光束的不同调制功能.通过等效介质理论,可以计算磁性电磁超构材料的等效电磁参数,从而获得等效折射率.而且,随着磁性柱半径的变化,可以实现等效折射率的灵活调制.尤为特别的是,通过改变外加偏置磁场的空间分布,可以实现不同的折射率梯度,这也是磁性电磁超构材料相对于普通介质体系的优越性.基于多重散射理论,对光束在二维体系中的传输行为进行了模拟计算,研究结果表明通过调制外加偏置磁场可以实现光束的囚禁、光束的内偏折和外偏折、以及分束等功能.而且,通过改变外加磁场可以实现不同功能间的切换,这种灵活的调制能力为光束传输提供了新的自由度. 相似文献
11.
We study numerically Akhmediev breather dynamics in optical fibers under initial conditions that do not correspond to an ideal infinitesimal modulation on a plane wave. We examine two modifications that are commonly encountered in realistic experiments: (i) a finite-amplitude (not necessarily weak) initial modulation; (ii) the use of pulsed excitation. In the first case, we derive an expression for the propagation distance required to generate a train of compressed breather pulses. In the second case, we show that breather dynamics with pulsed excitation can be interpreted in terms of local breather states at different points on the pulse envelope. 相似文献
12.
Ram Krishna Sarkar 《Optik》2010,121(4):339-346
In this paper, using parabolic equation approach, coupled propagation of two coaxially co-propagating and mutually incoherent bright cylindrical beams in saturable nonlinear medium has been investigated. Considering the coupling coefficient equal to unity (κ=1), a detailed account of formation of spatial soliton pair (i.e. both beams are stationary trapped) and spatial breather pair (i.e. width of each beam oscillates with the propagation distance) has been provided and existence of spatially trapped breather pair (i.e. average width of each breather of the pair does not change with the propagation distance) has been shown. Conditions of formation of trapped spatial breather pair and their existence line has also been revealed for arbitrary beam width ratio of the beams. It is revealed that spatial soliton pairs are just a special case of trapped breather pair. The regions (conditions) of mutual-focusing and mutual-defocusing of spatial soliton pair/breather pair have also been identified. Lastly, the law of trapped breather pair formation is proposed. 相似文献
13.
The interactions between two parallel and co-polarized beams in weakly coupled cubic focusing nonlinear waveguide arrays with transverse inhomogeneous modulation of the refractive index were investigated by means of beam propagation method. Results show that the in-phase beams attract each other and coalesce when the inhomogeneous parameter is smaller than a critical value. For the out-of-phase beams, oscillations exist at low power level, and the larger inhomogeneous parameter, the larger period and amplitude of oscillation. At a high power level, solitonlike propagation of weak coupling occurs. The inhomogeneity of waveguide arrays provide a flexible way to control the interactions of beams, and may find potential applications in all-optical systems. 相似文献
14.
15.
研究得到了偏离束腰入射的复宗量Laguerre-Gauss光束在强非局域非线性介质中传输的解析表达式,并且得到了其二阶矩束宽的解析解.通过例子研究了偏离束腰入射的复宗量Laguerre-Gauss光束在强非局域非线性介质中传输性质.结果表明:非(0, m)模的复宗量Laguerre-Gauss光束的光束形状随着传输而发生改变,并以Δz=πzc为周期做周期性演化.而(0,m)模复宗量Laguerre-Gauss光束在演化过程中则形状保持不变,仅改变光束宽度;不论功率多大,在偏离束腰入射条件下总是表现为呼吸子;只有当其为束腰入射,并且入射功率等于临界功率时才能形成孤子.
关键词:
强非局域非线性
复宗量Laguerre-Gauss光束
二阶矩束宽
空间光孤子 相似文献
16.
导出了高斯光束在梯度负折射率介质中的ABCD矩阵,据此得到光束在此介质中的传输模型.并利用此模型分析了高斯光束在梯度负折射率介质中的传输特性,发现它能产生空间孤子及呼吸子形式的传输,并发现光束的束腰半径不一定是最小束宽半径.还研究了梯度系数对介质聚焦能力的影响,据此可以设计出相应聚焦能力所需要的折射率分布.最后分析了传输时高斯光束曲率半径的变化情况,与光束束宽半径的变化显著不同,曲率半径始终从无穷大开始,然后产生一个个周期性的变换. 相似文献
17.
利用解析和数值方法研究了在具有横向折射率周期性调制的克尔型非线性介质中光学格子孤子的传输,得到了孤子参数的演化方程以及格子孤子的形成和稳定传输的条件.结果表明:当光束的入射角小于某临界角度时,光束可被类似波导形式的路径俘获而稳定传输,该临界角随折射率调制周期、调制深度的增加而增大,且光束越窄临界值越大.此外,线性空间啁啾虽然对光束传输的中心位置没有任何影响,但会导致光束发散从而破坏格子孤子的形成和稳定传输,对此提出了采用特定功率取值来补偿啁啾作用从而形成格子孤子的方案.
关键词:
光孤子
光学格子
光传输
矩方法 相似文献
18.
19.
Urszula A. Laudyn Katarzyna A. Rutkowska Robert T. Rutkowski Mirosław A. Karpierz Tomasz R. Woliński Jan Wójcik 《Central European Journal of Physics》2008,6(3):612-618
We have investigated the nonlinear propagation of light in photonic crystal fibers filled with nematic liquid crystals. We
analyzed a configuration with a periodic modulation of the refractive index corresponding to a matrix of waveguides. Matrices
of coupled waveguides allow observing a variety of new phenomena both for low power light beam propagation and with an existence
of nonlinear effects. The opportunity for the creation of solitary waves caused by the interplay between diffraction and nonlinear
effects in these kinds of fibers is investigated. At low power the propagating light beam spreads as it couples to more and
more waveguides. When the intensity is increased the light modifies the refractive index distribution, inducing a defect in
the periodic structure. The creation of such a defect can lead to a situation in which the light becomes self-localized and
its diffractive broadening is eliminated. Eventually, in the case of positive Kerr-type nonlinearity, a discrete soliton can
be created. In the case of negative nonlinearity the refractive index decreases with the optical power and can lead to bandgap
shifting. The incident beam, with a frequency initially within the bandgap, is then turned outside the bandgap resulting in
the changing of the propagation effect for the discrete diffraction effect. As a consequence the delocalization of the light
can be observed.
Presented at 9-th International Workshop on Nonlinear Optics Application, NOA 2007, May 17–20, 2007, Świnoujscie, Poland 相似文献