非局域自散焦克尔介质中空间光暗孤子成丝的理论与实验研究

摘要

对非局域自散焦克尔介质中的空间光暗孤子成丝进行了研究．理论上从非局域非线性理论模型出发，数值模拟研究了非局域程度和吸收系数对暗孤子成丝的影响．当入射背景光强一定时，非局域程度越大成丝起始点越远、成丝数量越少；而当入射背景光强与临界光强之比一定时，非局域程度基本不影响成丝起始点以及成丝数量，且非局域下的成丝数量与局域下一样．此外，当入射背景光强一定时，吸收系数越大成丝数量越少．实验上通过改变染料溶液的浓度以及背景光斑的椭圆率，分别研究了样品浓度和背景光斑椭圆率对暗孤子成丝的影响．当入射背景平均光强一定时，样品浓度越小成丝数量越少，背景光斑椭圆率越小成丝数量越少；而当入射背景平均光强与临界光强之比一定时，样品浓度基本不影响成丝数量．在实验中还观察到了光学冲击波现象．%In this paper, the spatial optical dark soliton filamentization in a nonlocal self-defocusing Kerr medium is investigated. Theoret- ically, starting from nonlocal nonlinear theoretical model, we examine the influences of the degree of nonlocality and the attenuation constant on the formation of dark soliton filaments by numerical simulation method. We find that when the input background optical intensity is determined, the greater the degree of nonlocality, the farther the initial poirit of the formation of dark filaments is and the less the number of dark filaments decreases with the increase of the degree of nonlocality; when the ratio of the background optical intensity to the critical optical intensity is fixed, the degree of nonlocality can hardly influence the number of dark filaments and the number of dark filaments under nonlocality is equal to that under locality. Besides, when the input background optical intensity is determined, the number of dark filaments decreases with the increase of the attenuation constant. Experimentally, by changing the concentration of dye solution and the ellipticity of background light, we discuss the influences of the concentration of sample and the ellipticity of back- ground light on the formation of dark soliton filaments respectively and find that when the input background average optical intensity is determined, the number of dark filaments decreases with the increases of the concentration of sample and the ellipticity of background light; when the ratio of the background average optical intensity to the critical optical intensity is fixed, the concentration of sample can hardly influence the number of dark filaments. Besides, the phenomenon of optical shock wave is found in our experiment.