Study On The Mode Of Laser Resonator

The output beam quality of the laser, which determined mainly by the laser mode inside the resonator, decides the characteristics of the transmission and focusing operation of the beam. The calculation of the laser mode shows its importance in the applications of laser machining and optical measurement. It provides the basis for the design of the resonators, external optical path and beam shaping system.The mode solutions of the typical resonators, such an plane parallel resonator and confocal shperical resonator, are given by analytic theory. But the relevant calculations of novel resonators and newly developed optical components show the limit of this method. Numerical methods, including Fox-Li iterative numerical method, Hermite Gaussian expansion, Fast Fourier Transform(FFT) mehtod, Finite Difference Method(FDM) and Finite Element Method(FEM), achieve in solving above problems. In particular the numerical Fox-Li iterative method, which is the numerical solution of a model commonly applied in a way, as long as enough sample points, which can be used to calculate any shape formed and began the self-reproduction mode, but also can be calculated, such as parallel planar cavity endoscopic tilt, mirror the non-formation of the mold etc. But its disadvantage is when the Fresnel number is large, the calculation of the heavy workload.In this paper, the characteristics of resonant cavity patterns, proposed a modified Fox-Li algorithm, whose main features are:multiple models can be solved, and very easy to judge the capacity of cavity identification of patterns. First of all, introduces the basic concepts of laser resonator and a variety of optical cavity mode calculation method, and compare the advantages and disadvantages of each method. Then were calculated in the stable and unstable resonator cavity case, the resonant cavity light field intensity distribution, phase distribution and the loss of a single iteration. To stabilize the diffraction loss by comparing the stability of diffraction loss when the value of the size of the obtained two types of cavity models of the election. For non-stabilized cavity, yet it gives the cavity length and the stability of the base model the impact of the value of diffraction loss.