[en] A possibility is studied of transformation of stored energy in inverse media with excited metastable molecules or atoms into energy of waveguide modes localized in a dielectric waveguide with small losses. A condition for generation is shown to fulfill for specific type of the localized modes of the closed waveguide. A grating of waveguides is investigated for a medium with homogeneous pumping. A flow of a stream of metastable species through a grating of independent waveguides is studied. The dependence is obtained of efficiency of energy transformation and dimensions of the region of generation on the spatial density of the waveguide surface. Numerical calculations are presented for O₂(a ¹Δ) and I(²P_1/2). Practical applications of a cavitiless waveguide laser are discussed. (author). 9 refs, 4 figs, 5 tabs