Abstract

Microwave techniques have been applied as alternative means to excite laser plasmas. However, there needs still the problem to be solved how the microwave power couples into the discharge region. An approximate calculation of the electrical field distribution in a waveguide by using the field code URMEL T will be presented. Utilizing the same code, a rectangular waveguide coupling geometry is optimized for the microwave L-band. The so determined coupling scheme has been tested using a CO₂ gas mixture for laser action. Furthermore, inserting a double ridge as part of the coupling structure yields, a high enough electrical field strength over density (E/N-) value to excite high pressure gas discharges such as rare-gas halide gas mixtures. A power of 2.5 megawatt of a pulsed microwave L-band generator is used to pump such a double ridge coupling geometry with a quartz capillary as a discharge tube. A XeCl excimer gas mixture was pumped up to the laser threshold without any preionization techniques. We believe this to be the first realization of a L-band pumped excimer laser in a rectangular waveguide. The evaluation of the used coupling structure features future design considerations.

© 1989 Optical Society of America