高斯光束经波长级圆孔衍射的轴上光强特性

基于横截面上精确表述的光强和精确的衍射场公式 ,对高斯光束经波长级圆孔衍射的轴上光强特性进行了研究。结果表明 ,高斯衍射光束的轴上光强特性取决于初始高斯半宽度w0 和波长级圆孔的孔径R。对于w0 /R≥ 1的高斯衍射光束 ,轴上光强存在的极值个数和出现的位置仅由比值m=2R/λ决定 ,最大的轴上光强均出现在N =R2 / (λz) =1的地方 ;至于轴上光强极值的峰和谷明显与否 ,取决于w0 /R的比值 ,比值越大 ,轴上光强极值的峰和谷就越明显。当w0 /R的比值足够大时 ,就趋向于平面波入射时的情形。而对于w0 /R<1的这一类高斯衍射光束 ,轴上光强存在特定的演化规律 :随着初始高斯半宽度的减小 ,轴上光强极值个数逐步减少直至全部消失。

Axial Light Intensity Characteristics of Gaussian Beam Diffracted by a Wavelength-Order Circular Aperture

Based on the accurate expression of light intensity at the transverse plane and the rigorous diffraction formulae, the characteristics of axial light intensity of Gaussian beam diffracted by a wavelength-order circular aperture are investigated. The results show that the axial light intensity characteristics of Gaussian diffracted beam are decided by the initial Gaussian half width w0 and the radius of wavelength-order circular aperture R. As to the Gaussian diffracted beams with w0/R≥1, the number and location of extrema of axial light intensity are determined by 2R/λ, and the maximum axial light intensity must be located at N=R2/(λz)=1. Whether the apex and vale of extrema are distinct or not rest with the ratio of w0/R. The larger the ratio, the more distinct the apex and vale are. When the ratio of w0/R is large enough, it trend to the case of planar incident wave. While for the Gaussian diffracted beams with w0/R<1, the axial light intensity exists specifically evolutive law. The number of extrema is reduced step by step and finally disappeared with the initial Gaussian half width diminishing.