In this paper we discuss the possibilities and realization in high-power systems of a narrow-band reflector with adjustable high reflectivity and with continuous tuning over a large frequency region. We describe a design for both low- and high-gain systems. For the experimental realization of a low-gain system we used a CO
2laser and studied a continuous range of 65 transitions of the

and 13 transitions of the 01
11-11
10 vibrational band. With a cavity containing a dc discharge 130 cm long, for each band we found a continuous range of single oscillating transitions with output powers up to 15 W. Finally, we propose an experimental solution for continuous tuning of a high-gain system as, for instance, the central part of the

vibrational band of CO
2.