Study of spectral dependence of fluorescence lifetime of acridine orange in one-dimensional photonic crystals

The spectral dependences of fluorescence intensity $I$ and average lifetime of excited state $\tau$ of acridine orange (AO) molecules embedded in one-dimensional photonic crystals (PC) at different radiation detection angles were studied. The density of electromagnetic modes of PC was calculated using the scattering matrix method. The spectral characteristics of AO fluorescence in PC samples and samples with permanent pores (porous silicon) were compared, as well as with the calculated dependences of the relative density of electromagnetic modes. The kinetics of AO fluorescence decay in PC were studied at different wavelengths, which were approximated by two exponentials. It was found that short-term luminescence is practically independent of the wavelength, while for long-term luminescence a non-monotonic dependence on $\lambda$ is observed with a minimum corresponding to the photonic band gap. The Purcell factor was estimated for the studied systems. It was proven that the experimentally obtained dependences of the energy and time characteristics of AO fluorescence on $\lambda$ are due to a change in the density of photonic states.