环形光束的非线性传输及聚焦特性研究

针对用于产生光镊的环形光束,利用分步傅里叶-贝塞尔变换算法,对二维环形超高斯光束的非线性传输及聚焦过程进行了数值模拟,给出了环形光束聚焦场附近的光强分布,并分析了非线性调制对聚焦性质(包括焦面中心光强、焦面光强的横向分布、轴上光强和光束质量)的影响.研究表明,从聚焦角度来看,非线性调制中的位相调制比振幅调制对环形光束聚焦性质的影响程度要大;从非线性传输角度来看,随着非线性介质长度的增加,位相调制和振幅调制对环形光束聚焦性质各有不同程度的加剧,其中非线性作用对振幅调制的影响要比位相调制明显.

Nonlinear Propagation and Focusing of Annular Laser Beam

This paper aims at the annular beam used for generating the optical-tweezer.The nonlinear propagation and focusing process of two dimensions annular super-Gaussian beam have been numerically simulated by using the split-step fast Fourier-Bessel transform (SSFFT) methods and the intensity distribution in the vicinity of the focusing field of the annular beam has been gotten. The effects of nonlinear modulations on the annular beam focusing properties, including center intensity of focal plane, the transverse distribution of the focal plane intensity, the intensity on optical axis and the beam quality, have been investigated. On the aspect of focusing angle, it is found that the phase modulation plays more influence on the focusing properties of annular beam than the amplitude modulation. On the aspect of nonlinear propagation angle, it can be seen that the increase of nonlinear medium length strengthen the influence of amplitude modulation and phase modulation on the focusing properties of annular beam in different degrees, and amplitude modulation is more susceptible to nonlinear effects than phase fluctuations.