Study On The Beams Quality Of Nonparaxial Scalar And Vectorial Beams

In Laser Optics the laser beam quality of is a classic and new topic. Because it concerns not only the characteristic parameters and methods of the beam quality, but also the problems of the descriptions of laser beams, the knowledge of the law of the propagation and transformation of laser beams etc. Especially, in recent years with the advent of diode lasers, micro-cavities and photonic crystals etc., the study of nonparaxial beams whose width is comparable with the wavelength and/or divergence angle is large becomes more and more significant. Considerable attention has focused on the characterization of nonparaxial beams and their beam quality. On the basis of the second-order moment of the power density, the nonparaxial vectorial moment theory of light beam propagation , and the extended power in the bucket (PIB), or equally, β parameter, the purpose of the present dissertation is to study the beam quality of nonparaxial scalar and vectorial beams. The main results obtained are summarized as follows:1. Based on the Rayleigh diffraction integral and without use of the usual approximation, R≥λ(λ-wavelength), an exact analytical expression for the axial intensity of nonparaxial Gaussian beams diffracted by a small circular aperture is derived. Then, by using the conventional intensity definition and accurate intensity expression, a comparative study is made. It is found that the difference between the two definitions depends on the f-parameter, truncation parameter Sand propagation distance z.