Interferometry of resonator modes in submillimeter wave lasers.

Submillimeter wave gas lasers are characterized by low Fresnel numbers and by gain widths smaller than the mode separations. This allows interferometry of laser emissions and resonator modes with the aid of the laser resonator. The theory of Bergstein and Schachter on modes occurring in resonators with low Fresnel numbers is compared with the experimental data obtained by laser resonator interferometry. The influence of the tilt of a resonator mirror on the intensity of the laser emission is measured for different modes.