Coupling losses in hollow waveguide laser resonators

Hollow waveguide gas lasers of the type described by Smith have some inherent loss in coupling radiation from the guide into free space and back into the guide. This paper calculates that loss for the EH11lowest order waveguide mode as a function of mirror position and mirror radius. It is shown that some mirror positions and radii are optimum, in that they provide low coupling loss and are relatively insensitive to mirror position.