By using optics matrix and equivalent confocal resonator method,the method of designing configuration of cavity for mode match is calculated.

Simulation of the Mode-field distribution of symmetricconfocal resonator;

Measuring the laser longitudinal mode based on the confocal resonator;

In this paper, the Field-change function in confocal resonator is derivedfrom the diffraction theory.

Based on cavity ring-down spectroscope technology,a single wavelength reflectivity measuring system whose ring- down cavity is confocal cavity is set up.

Approximate condition of reflectivity measurement with cavity ring-down method is analyzed,misadjustment characteristic of confocal cavity is discussed and influence of cavity mirror’s reflectivity on ring-down signal is calculated.

Based on the “inversion” of the half confocal cavity and the curve of gain distribution in the discharge zone,the various laser output patterns can be acquired by adjusting an infra red coupling mirror coated with high reflective film.