Study On Propagation And Spectral Properties Of Partially Coherent Light Passing Through An Optical System With Aberration

The focusing and spectral properties of laser beam are topics of current interest, which play an important role in development of the modern optics theory and laser technologies. Starting from the propagation law of partially coherent light and using a typical partially coherent light, i.e., Gaussian Schell-model (GSM) beam describing the multimode laser in practice, I present in this dissertation the research results on propagation properties and spectral changes of partially coherent light passing through an optical system with aberration.A comprehensive review of the basic analytical methods for the beam transformation including the matrix optics method and diffraction integral method is summarized. And several beam models for the partially coherent beam are introduced, which include GSM beam, partially polarized Gaussian Schell-model (PGSM) beam and isotropic twisted Gaussian Schell-model (TGSM) beam et al. Based on the above theory and methods, the main works of this thesis are listed as follows:Starting from the transfer matrix of optical system and propagation law of partially coherent light, the expression of GSM beam passing through an astigmatic aperture lens is derived. It is shown that the axial irradiance distribution, the maximum axial irradiance and its position of focused GSM beams by an astigmatic aperture lens depend upon the astigmatism of the lens, the coherence of partially coherent light, the truncation parameter of the aperture and Fresnel number. The numerical calculation results are given to illustrate how these parameters affect the focusing property.Starting from the propagation law of partially coherent light and beam coherence-polarization (BCP) matrix approach, the properties of PGSM beams through an aperture lens with spherical aberration are studied. The propagation equations of PGSM beams are derived, which enable us to study the axial polarization changes and irradiance distributions of PGSM beams through an aperture lens with spherical aberration. Detailed numerical results show that the spherical aberration affects axial polarization and irradiance distributions. At the same time, the focal shift and focal switch of PGSM beams passing through a system with the aperture and spherically aberrated lens separated is studied in detail. Our main attention is focused on the effect of spherical aberration and partial coherence on the focal shift and focal switch of PGSM beams.Starting from the propagation law of partially coherent light, the spectral shifts and spectral switches of GSM beams focused by an astigmatic aperture lens are studied. As compared with the aberration-free case, where the spectral change is only correlation-induced, the astigmatism of lens affects the spectral behavior of GSM beams. The astigmatism of lens can change the position where the spectral switch appears, and the position shifts towards the focal plane obviously. However, the spectral switch disappears when the astigmatism is big enough.Basing on the diffraction integral method, the spectral changes and spectral switches of TGSM beams diffracted by an aperture are studied. The influence of the twist factor on spectral changes and spectral switches of TGSM beams is emphasized. It is shown that the twist factor can change the critical position where the spectral switch takes place. And the spectral minimum Smin increases and transition height ? decreases with increasing twist factor. In addition, Spectrum of GSM beams without aberration through an aperture can be treated as special case ofμ=0.