Near- and far-field laser modes produced by confocal unstable resonators. I. Free-space and saturable gain media

Abstract

Optical modes produced in positive branch confocal unstable resonators have been obtained using the method developed by Rensch (1974). The limitations and advantages of using a finite difference scheme are highlighted by examination of the modes produced under free-space conditions. A typical gain medium produced by an air-breathing gas dynamic laser is then modelled and introduced into the resonator code. The effect of magnification on medium saturation and also the power extracted is then investigated. In all the examples used far-field conditions are also obtained by Fourier transforming the extracted near-field mode. A visual display of the three-dimensional effects is presented by hidden line plots produced on a calcom plotter.

LIMP in continuously coupled unstable resonators

“…The inclusion of these high frequencies would provide higher spatial frequency components of the refractive index perturbations. The refractive index data was combined with a computer code developed by Jones (1978) and modified by Davies et aZ(l980) to include continuously coupled non-confocal unstable resonators. The computer code calculates, by solving the paraxial wave equation using a finite difference technique, the far-field intensity distribution obtained from an unstable resonator with or without refractive index perturbations present.…”

Numerical predictions of phase distortions due to a heating differential in a CO2laser discharge tube

“…In order to assess accurately the effect that the density perturbations have on the exit wavefront, and hence on the far-field output beam, the density variations should be included in a three-dimensional unstable resonator code, such as that developed by Jones (1978). However, we hope to obtain some idea of the effect on the quality of the output beam by assuming that the wavefront has a constant amplitude over the .…”