Tunability characteristics of waveguide CO(2) lasers with internal etalons

We investigate the possibility of increased tuning range of waveguide CO(2) lasers by using a longer discharge and a tilted intracavity etalon as axial mode selector. Taking into account etalon losses, the tuning range was calculated as a function of laser gain, pressure, and discharge length. Improvements depend strongly on the index of refraction and the absorbtivity of the etalon material. The comparison with a length-restricted laser without mode selection shows that the use of a CdTe etalon in a laser with 25-cm active length could increase the tuning range from 1.5 GHz to 2.2 GHz. However, an air etalon reduces the bandwidth due to higher tilting losses.