The modulation diffraction rings of a intense laser beam propagation in linear medium is investigated numerically by a two-dimensional fast Fourier transformation algorithm. The definition for Fresnal number in linear mediums is given on the basis of the properties of the diffraction rings land the relationship between the number of diffraction rings and Fresnal number is obtained.
Numerical calculations indicate that, in order to effectively suppress the diffraction modulations of intensity, it is necessary to choose the order n and half-width ws of super-Gaussian apertures (e.g. n=4, ws=0.4mm) properly.
If the aperture parameters are chosen appropriately, the serrated aperture will enable us to reduce the diffraction modulations of axial intensity in the region which we are interested in (F=20). Furthermore, the super-Gaussian aperture can suppress the diffraction modulations in the most of Fresnel region (F >3.7).
It is shown that,while maintaining a relatively large fill factor,the use of serrated apertures can suppress the diffraction modulations of axial intensity and reduce the nonuniformity of transversal intensity distributions.
This article utilizes the non- contact optical technique, mainly studies the liquid low-frequency surface wave characteristic and has established the interference -diffraction modulation effect intensity distribution and the liquid surface wave relations.
The intensity distribution of light, interference fringe and its characters are analyzed and the angle width of the interference fringe range with SAW was derived by theory of wave optics under the action of modulation.
The features of Fresnel diffraction was fully characterized for the serratedaperture in this paper, we have proposed and demonstrated that modulated sinusoidalserrated apperture can effectively suppress the near-axis intensity ripples for a large scaleof Fresnel numbers. The design procedure was also given for its application in the highpowers laser systems.
The features of Fresnel diffraction are studied of the serrated aperture in this paper. We have proposed and demonstrated that using a serrated circular aperture and a spatial filter could effectively improve the light beam uniformity and suppress the intensity ripples for a large Fresnel numbers.
In order to improve the near field uniformity of the "SG Ⅱ"laser beam, we haveproposed and designed a special beam,called flat-top centered dip beam.The beam isgenerated by a combination of a hard edge serrated aperture and a spatial filter.In the paperthe calculated results and the inveStigated characteristics of the designed beam are alsogiven.