New approach to the theory of irregular lossy waveguides and its application to design of teraherz gyrotrons

A new method for analysis of longitudinally inhomogeneous lossy waveguides is developed. It takes into account local boundary conditions in a rigorous manner. It allows us to reduce the problem to the set of ordinary differential equations similar to the lossless case. Calculation of field distributions and quality factors of a terahertz gyrotron cavity is addressed as an example. It is shown that dissipation and conversion TE modes cannot be neglected. In the case considered they notably influence quality factors of the cavity eigenmodes.