Kirensky Institute of Physics, Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences, Россия

The development of photonic-crystal structures with tunable optical properties is of great interest in modern photonics. A promising approach involves the introduction of defect layers based on cholesteric liquid crystals, whose optical parameters are sensitive to external fields and helix pitch value. The doping of such structures with biological pigments (e.g., carotenoids) is of particular interest, as it enables the control of optical modes via resonant absorption by the dye and its dichroism. In this work, we model the spectral and polarization characteristics of a photonic-crystal structure with a defect layer composed of a cholesteric liquid crystal doped with β-carotene. The photonic-crystal structure consists of alternating layers of titanium dioxide and silicon dioxide. A cholesteric defect layer is placed in the center of the structure. The transmission, reflection, and absorption spectra are calculated for two orthogonal linear polarizations of incident light and at various values of the cholesteric helix pitch. A comparison of the results obtained with and without accounting for pigment dispersion shows additional suppression of transmission within the photonic band-gap, attributed to light absorption by the dye. Thus, the introduction of an absorbing layer leads to a significant change in the intensity of localized resonant modes and a reduction in transmission and reflection peaks. The present study also investigates the dependence of the spectra on the incident light polarization. In the spectral region of the β-carotene absorption, the calculated characteristics of the structure differ significantly for the two polarizations of light, indicating the presence of linear dichroism in the studied system. Consequently, the difference in absorptance results in unequal suppression of the resonance modes. This research was funded by the Russian Science Foundation (project no. 24-12-00236).