非偏振贝塞尔高斯光束的球散射

Scattering of Unpolarized Bessel-Gauss Beams by a Sphere

无衍射光束球散射性质的研究目前一般采用贝塞尔光束,但是贝塞尔光束在物理上是不可实现的。贝塞尔高斯光束作为近似无衍射光束,是亥姆霍兹方程在傍轴条件下的解,并且可以用激光振荡器直接产生,但其光束宽是有限的。应用傅里叶变换,平面波谱展开和球面矢量波函数展开法,推导了非偏振贝塞尔高斯光束的球散射远场的无量纲散射函数。通过数值模拟,对非偏振的贝塞尔高斯光束与贝塞尔光束,高斯光束的球散射远场进行了比较,比较发现:当球散射体偏离光轴时,非偏振贝塞尔高斯光束跟贝塞尔光束散射远场的差异主要是散射强度的差异,但是散射极点所在的方向基本保持不变;贝塞尔高斯光束和贝塞尔光束的散射在光束圆锥角方向上比较显著,但高斯光束的前向散射比较显著。

The Bessel beams are often used for investigating the scattering properties of the non-diffracting beams, but the Bessel beams cannot be realized physically. As the pseudo-nondiffracting beams and the exact solution to the paraxial Helmholz equation, the Bessel-Gauss beams can be generated directly from the laser resonator and possess finite spatial width. The dimensionless scattering function is derived for the Bessel-Gauss beams scattered by a sphere by means of Fourier-transform, the plane wave expansion and the vector spherical wave expansion. By numerical simulation and comparison with that of the Bessel beam and the Gauss beam, it can be found that only the scattering intensity is influenced as the spherical scatterer is shifted off the beam axis, the directions where the scattering extreme points exist almost keep no changes. The scattering is dominant in the direction of the conical angle for the Bessel-Gauss beam and the Bessel beam, but for the Gauss beam the forward scattering is always dominant.