RADIO PHYSICS AND RADIO ASTRONOMY

Subject and Purpose. The study concerns spectral transformations of the broad-band radiation generated in polyurethane matrices doped with the Rhodamine 6G organic dye. The purpose is to identify the effects due to thickness of the active layer and dye concentration therein upon the efficiency of luminescent light conversion, and their possible applicability in luminescent spectral converters and solar concentrators.

Methods and Methodology. The matrices were fabricated, proceeding from a two-component polyurethane mixture Crystal Clear 204 with a variety of dye concentrations. The study involved measurements of absorption spectra, parameters of luminescence, and optical density of the specimens. The transformation efficiency was evaluated by analyzing the spectral distribution of radiation intensity at the input and output of the matrix, followed by numerical integration within the frequency range of luminescence.

Results. As has been found, thinner matrices (e.g., 1 mm thick) demonstrate efficient re-emission of light under the conditions of an optimal dye concentration (about 0.1 mM). Higher concentrations lead to losses in efficiency due to self-absorption of the radiation. Thicker matrices (about 5 mm thick) exhibited significantly lower efficiency due to their increased optical density and higher losses associated with extinction and reabsorption effects.

Conclusion. The polyurethane matrices are promising materials for phototransformation-based applications, particularly in thin-film configurations. Further optimization of their optical properties and employment of dyes characterized by higher Stokes shifts would be required for application in bulk systems.

Keywords: luminescence, spectrum converter, polyurethane, Rhodamine 6G, spectral transformation, solar concentrators

Manuscript submitted 04.05.2026

Radio phys. radio astron. 2026, 31(3): 179-189

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