Transmission losses and mode-selection characteristics of a curved hollow dielectric waveguide with a rough surface

The effects of surface roughness and axial bends of a hollow dielectric waveguide on transmission of 10.6-μm CO2 waveguide laser radiation are measured. An analytical expression for various waveguide modes has been obtained in the beam approximation for calculating the value of the transmission of a real waveguide. This expression takes into account both Fresnel losses and radiation scattering due to the roughness. It is shown that the efficiency of selecting transverse modes from the waveguide laser is diminished with an increase in the bending radius and the waveguide diameter and also with a decrease in the radiation wavelength.