Effects Of The Obscuration Ratio Of The Optical System On Transmission Properties Of Polarized Beam

The propagation and transformation of the laser beam are frontal topics in the field of laser research. How to determine the re-distribution of the beam after passing through the optical element is a major problem. Some of the optical systems have higher requirements to polarization properties of the beam, but so far not much is completed. However, making a qualitative and quantitative analysis to the polarization state of light beam passing through the optical system, can effectively improve the polarization effect problems presented in the optical system, which is a certain reference and guidance to optical design. In this paper, the intensity and polarization characteristics of completely polarized Gaussian-Schell model beam passing through the optical system are studied.First, according to the extended Huygens-Fresnel principle and Collins formula, based on complex Gaussian function expansion method, the cross-spectral density formula of elliptically polarized Gaussian Schell-model beam passing through the rectangular aperture is derived. And combined the Stokes vector theory, the expressions of light intensity, the degree of polarization, the orientation angle and the degree of ellipticity on the receiver plane are studied. Secondly, the change in light intensity with the transmission distance is numerically analysed at different wavelengths and different aperture obscuration ratios, as well as the change of the orientation angle and the degree of ellipticity at different aperture obscuration ratios and different diffraction angles.Meanwhile, based the unified theory of coherent and polarization, the change in the spectrum density (ie, intensity) and the degree of polarization of the elliptically polarized Gaussian Schell-model beam passing through the rectangular aperture is analysed, as well as the effect of the spectrum density, the diversification of the polarization, the aperture obscuration ratio and the initial degree of coherence on the Gaussian-Schell model beam passing through the aperture. The results show1) Effects of the aperture obscuration ratio on light intensity of elliptically polarized GSM passing through the aperture is obvious in the near-field zone, which varies with oscillations, and the oscillation is stronger for larger aperture obscuration, meanwhile, it changes in different wavelength, the variation in the near field zone is stronger for larger wavelength in the same aperture obscuration ratio. Nevertheless, intensity distribution of elliptically polarized GSM is less sensitive to the aperture obscuration ratio and wavelength with the transmission distance in the far-field region.2) Effects of the aperture obscuration ratio on polarization properties of elliptically polarized GSM passing through the aperture is obvious in the near-field zone, which varies with oscillations, and the oscillation is stronger for larger aperture obscuration, as well as the variation of the degree of polarization, the orientation angle and the degree of ellipticity, in addition, they change in different diffraction angles, the variation in the near field zone is stronger for larger diffraction angle in the same aperture obscuration ratio. However, with the transmission distance, the degree of polarization, the orientation angle and the degree of ellipticity of elliptically polarized GSM is less sensitive to the aperture obscuration ratio and diffraction angle in the far-field region.3) The spectrum density and the degree of polarization of elliptically polarized GSM passing through the aperture exhibit variation with oscillations on a certain transmission plane. The methods of cross-spectral density and Stokes parameter, by which the spectral density and the degree of polarization are described, are essentially the same. Equally, the degree of polarization of the beam is affected by the aperture obscuration ratio, and the impact increases with the aperture obscuration ratio. Simultaneously, the degree of polarization of the propagation light field varies with the initial degree of coherence, which further illustrate that the polarization and coherence does exist correlation.