POLARIZATION STATES AND OUTPUT POWERS OF A CO2-LASER WITH AN ELECTROOPTIC PHASE RETARDER

We study the power output and polarization state of a CO2 laser that c ontains both passive polarization-sensitive elements (Brewster plates) and an active phase-retarding electro-optic modulator (CdTe crystal). The theoretical threshold condition (i.e., the retardation required t o extinguish the laser) is obtained from a cavity round-trip Jones mat rix. We show that adding extra Brewster plates may be counter producti ve in that the required retardation voltage increases. We calculated t he output power, which depends on the saturated gain properties of the active media, by iterative modeling, with the elliptically polarized light propagated repeatedly around the cavity. We compare the theory w ith results from a folded rf-excited waveguide CO2 laser (Laser Ecosse Model CM3500). Theory and experiment are in fair agreement for low po wers. As expected, at high powers there are extra difficulties in mode ling the cavity behavior, probably because of distortions induced in a nd by the crystal.