Research On Effects Of The Aperture Of The Optical System On Transmission Properties Of Laser Beams

In the modern era,the propagation and transformation of the laser beam are hot topics in the field of laser research,to resolve the problem of the laser beams can regarded as one of the most important of laser optics. If the complex amplitude distribution on the plane of the laser beams as a known quantity, how to determined the complex amplitude distribution of the emission surface of laser beams through the optical system or a optical system that containing a aperture and other optical elements is a main research question in the laser optical field. Some optical system required of the beam polarization properties, however, there are some special optical systems, such as multi-optical systems, optical fiber distribution system has more requirements on the distribution of the aperture in the optical system. But for now, less report focus on the transmission characteristics of the polarization beams through different shapes of aperture(especially the distribution of the matrix aperture). The state of polarization of the laser beams will affect the image quality of the optical system (for example, having a large numerical aperture of the optical system), and the transmission characteristics of different nature of the laser beams through the different will being different,so the study of the transmission characteristic of laser beams through different shapes of the aperture, its findings has a guiding role on the actual optical system designed to control the laser beam.At first, in this paper, taken the polarized flat-topped Schell-model beams as an example, based on unified theory of coherence and polarization of beams and complex Gaussian function expansion method, combined with Collins formula, according to Stokes vector theory, the cross-spectral density formula,light intensity, the degree of polarization are derived. Then taken non-polarized flattened circular Gaussian beams as an example, study on its light strong distribution through different forms of aperture. Finally, the polarization state distribution of polarization beams was introduced in this paper. The results of this paper are listed as follows:(1)The polarized flat-topped Schell-model beams diffracted through two types of aperture, the effect of the wavelength,the size of the hole on the light intensity, truncation parameter of aperture greater impact in the near-field region, and accompanied by strong shock phenomenon, at a wavelength of certain circumstances, the circular hole the size of the impact on the near-field light beam to the transition from the far-field diffraction. As the distance increases, the energy of the beam itself weakened, wavelength, hole size, and the influence of truncation parameter of aperture becoming weaker.(2)After the polarized flat-topped Schell-model beams diffraction through an matrix of circular aperture, the degree of polarization depend on the effect of the X-axis diffraction angle, truncation parameter of aperture vigorously, but the spatial coherence length do less for the degree of polarization. However, for square hole aperture, the degree of polarization depend on the effect of the X-axis diffraction angle, the spatial coherence length significantly, but truncation parameter of aperture is less sensitive to the degree of polarization.(3)Non-polarized flattened circular Gaussian beams diffracted by different shapes of aperture. The shape of the aperture exerts a greater impact on intensity distribution in the transmission distance z/z0< 2, after the transmission distance z/z0> 2 the magnitude of this effect gradually disappeared, and finally light strong curve will become more stable.