Random lasers are new class of coherent light sources which inherent feature is positive feedback formation due to multiple light scattering in the active medium. Lasing threshold decreases under growth of the scattering efficiency. In the case of known random lasers multiple scattering is achieved by high concentration of fine dispersed particles (10⁸-10¹¹cm^-3) embedded into the active medium (solid or liquid solution of dye) or by dispersity of the medium itself (semiconductor powder). The scattering efficiency in the suspension depends on relative refractive index of the scattering centers, their effective size and concentration. But as the refractive index of polymeric matrix is high the relative refractive index of the highly refractive materials (rutile, diamond) is n_rel>1.6. Moreover the homogeneity of particle distribution in the medium is difficult to be achieved that influences the random laser parameters. The close value of the relative refractive index (n_rel =1.5) can be obtained using gas vesicles in the active medium.

In the work we investigated the lasing threshold and the lasing spectra (pumped by Q-switched YAG:Nd³⁺laser) parameters of the random laser based on films of solid polymeric dye (R6G, concentration 10^-3M) solution with N₂ vesicles as scattering centers. The vesicles parameters were varied by the intensity and duration of UV irradiation. The investigations were carried out depending on the vesicles concentration, films thickness (15-30mkm) and the polymer composition.

According to obtained results all the films possess the ability for lasing with lower lasing threshold and narrower lasing spectra when compared to suspension and dispersed media. The further decreasing of the lasing threshold can be predicted under optimisation of dye concentration and vesicles concentration and size. The obtained results allow asserting that investigated polymer films can be perspective to produce compact random laser.

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3. Wavelength Tunable Random Lasers
4. Strongly scattering active media as small-size frequency tunable sources of stimulated emission
5. Multiple scattering use for varying the luminescence spectra of the luminophors
6. Spectral Properties of the Dye Activated Polymers with Added Fine Scattered Particles
7. The Dye Activated Polymers with Added Fine Scattered Particles as New Lasing Media