A comparative analysis of the spectral-luminescent characteristics and generation parameters of a number of 3-imidazopyridylcoumarin derivatives has been carried out under nano-and microsecond excitation by coherent and incoherent light. New coumarin dyes are offered that feature the ability to lase under different types of pumping in the spectral range 525-580 nm; high lasing efficiency reaching 20% and 1% under laser and lamp pumping, respectively; and high photochemical stability (3-5 times higher than that of rhodamine 6G) under conditions of powerful nonmonochromatic pumping.Introduction. About 500 laser dyes of various classes have now been studied [1]. Relationships between their molecular structural features and spectral-luminescent and generation characteristics have been established. Recommendations for the synthesis of highly efficient compounds with long operational lifetimes have been developed. As a result, generation in the spectral range from the near UV to the near IR has been achieved [2][3][4][5][6][7][8]. Recently liquid solutions have been replaced by solid-state matrices [9][10][11][12]. However, such a broad spectral range does not mean that dyes that generate with high efficiency, are photochemically stable to UV pumping, and have increased operational lifetimes are available over all ranges. In particular, such "gaps" exist in the green-yellow spectral range where the known dye unsubstituted rhodamine cannot satisfy the whole set of parameters. Therefore, it seemed interesting to use coumarin dyes that are currently capable of generating from the blue to the red spectral range and exhibit high conversion efficiency and photochemical stability [2-4, 7-10].Experimental. Spectral luminescent characteristics of dye solutions were studied on the nanosecond pulsed spectrofluorimeter that was described before [8]. Fluorescence decay times were measured using the laboratory setup operating in time-correlated single-photon counting mode that was described before [11].Generation parameters of EtOH solutions of coumarin dyes with microsecond pumping were studied in a dye laser converter (Fig. 1). The source of microsecond coherent pumping was a dye laser (DL) based on an upgraded version of the coaxial lamp-cuvette construction of Dzyubenko [13]. The DL cavity was formed by a planar dielectric mirror with R = 100% and a stop of three plane-parallel plates of K-8 glass, which in this instance was the optimum exit mirror. The flash loop included 10 K75-48 low-inductance capacitors of total capacitance 2.2 μF connected in parallel and an IRT-6 ignition discharger. The input potential was 17 kV. The lamp discharge gap was filled with Xe at 20-30 Torr pressure. The pulsed pumping light pulse length at the 0.5 level was 2 μs with a 0.8 μs rise time. The pumping pulse electrical energy was 300 J. The first stage (A) of the laser converter used solutions of the studied coumarins for the pumping lamp (noncoherent). The cavity of the second stage (B) of the laser converter was formed by a planar blank mirror ...

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