Lasing of 2D short-range photonic crystals made of dyed vesicular polymer

Abstract

The random lasing of R6G-dyed vesicular polymeric films was investigated. The short-range ordering of vesicles allows classifying the films as 2D short-range photonic crystals. Nevertheless the ordering causes neither resonant nor interference conditions in this medium but the films reveal good lasing parameters: low lasing threshold and high luminescence-to-lasing transition rate. The obtained lasing spectra reveal quasi-linear structure when pump intensity is considerably above the lasing threshold and the dye concentration is over2*10 -3 M/l. All spectral lines are good reproducible from shot to shot. The dye concentration as well as pump intensity do not influence the frequencies of spectral lines. In the absence of any resonant conditions, we discuss the latent vibronic structure of the fluorescence spectrum and Raman scattering revealing as the most probable reasons for the random lasing spectrum structure. The Raman and vibronic frequencies are compared with the observed lasing spectrum lines. Good correlation between the lasing and Raman frequencies is shown. The mechanism of the quasi-linear lasing spectrum formation by amplification of the combined radiation of resonant Raman scattering and luminescence up to saturation is proposed. The random lasing spectrum in diffusive regime is denoted to provide a new way of laser dye Raman scattering investigation.

Coupled effect of stimulated Raman scattering and random lasing of dyes in multiple scattering medium

“…We have investigated the radiation spectra of three dyes: rhodamine 6G (R6G), rhodanine B (RhB) and dye №920 (structure formula in [6]) in three different MSM subjects to intensity of pump radiation. The first two dyes were incorporated in vesicular polymeric films, which are very effective MSM [4,7], where multiple scattering of light was caused by closely packed micron vesicles (mean diameter 1.2 μm) of nitrogen having relative refractive index n = 1.5. This scattering is caused not only by Fresnel reflection at the polymer/ vesicle interface but also by internal reflection of the light propagating in the polymeric media of more refractive index than vesicles.…”

“…It causes so-called random lasing (RL) arising in a dyed multiple scattering media (MSM) under intensive laser pump [1]. Usually MSM is concentrated suspension of high refractive dielectric microparticles in dye solution [1][2][3] or dyed vesicular polymeric films [4][5][6]. Radiation of dye is confined in MSM similarly to a cavity of a conventional laser due to multiple elastic scattering by the microparticles or vesicles.…”