Abstract
A mode calculation code in stable resonators was developed using the fast-Fourier-transform method, which can simulate a competition between two beams in the same active medium, such as two linearly-polarized beams. The code developed can be applied to a calculation of amplification characteristics by its sheet active region approximation, a calculation of oscillation characteristics in a large-Fresnel-number resonator by means of D. Phelps' method, and a calculation of multimode oscillation characteristics by using average field intensity as the laser beam intensity in gain coefficient calculation.
The code is applied to calculations of planes of polarization for higher order beam modes to show that a degeneracy of two modes with 90 degree out of phase leads to a linearly-polarized oscillation of a higher order mode, and to explain a well-known experimental result that such a higher order beam mode as TEM01 can be linearly polarized. The code is also applied to calculations of beam diameters. And the calculated results are presented.
