Numerical Simulation for the Diffraction Properties of Laser Zone-plate
激光波带片衍射性质的数值模拟

On the basis of Helmhots-Kirchohoff diffraction integration,Axial and radial intensity distribution and diffraction pattern of Frenel zone plate for Gaussian laser beam were analyzed theoretically.Numerical results showed that it presented a series of focal points on axis,around each of which there is oscillation of intensity distribution,with the increase of order number of focal point,the intensity increasing rapidly.There were phenomena of focal shifts,and focal shifts increased with the rise of the order number of focal point.The focal depth reduced on inverse square law with the rise of the order number of focal point and increasewith the reduction of zone number or the increase of focal length.On focal planes,the size of light spots was proportional to the width of the most external circle and inversely to the order number of focal point.