Novel distributed feedback gas lasers

Theory and first realization of three types of distributed feedback (DFB) gas lasers are reviewed. These are the linear DFB gas laser, the helical DFB laser, and the grazing-incidence gas laser (which is related to the second-order DFB effect). The realization of these novel types of lasers was achieved by incorporation of linear periodic, helical and wedged grating metal waveguides in an optically pummped far-infrared 496-micron CH3F laser. Helical DFB represents a new laser concept which is also of interest in microwave techniques and in research on dye lasers and cholesteric liquid crystals. A goal of future studies on DFB gas lasers is the realization of 10-micron CO2 DFB lasers which promise excellent characteristics and applications.