Designing Waveguide Couplers for Microwave Excitation of Laser Gases.

The goal of this thesis is to develop an analytical model from which a waveguide coupler can be designed. The specific application considered here is to use a waveguide coupler to excite a plasma tube inside a waveguide. This application is desirable for use in laser systems. The approach taken is to model the plasma as an equivalent dielectric centered in the secondary waveguide. Standard waveguide analysis techniques are used to find a perturbed propagation constant in that waveguide. Successive approximations are made to the coupled wave equations until a piece-wise linear solution is obtained. This solution gives the field distribution resulting from any arbitrarily chosen coupling geometry. Thus, the distribution for any desired coupling characteristics can be determined in an iterative manner, essentially by trial and error. Preliminary tests were made on couplers designed using the model initial results are promising but inconclusive. It is believed that this design method will provide the tool for designing couplers to obtain a desired field distribution in the secondary waveguide. Author