Dependence of cooperative emission spectra of complex organic molecules on exciting photon energy

Abstract

The dependences of cooperative emission, superfluorescence, and lasing spectra on the wavelength of pumping radiation were studied for highly concentrated ethanol solutions of organic dye molecules. The relative intensity of cooperative emission was found to decrease, while the intensities of superfluorescence and lasing were found to increase with the energy of exciting photons. The increase in the dephasing rate of quantum states is supposed to be primarily responsible for the change in proportion between these intensities. On increasing the dephasing rate, with all other factors being the same, the concentration of the excited molecules with the phased quantum states decreases, while that with the dephased states increases. The ratio between the cooperative emission and dephasing rates determines the proportion between the intensities of cooperative emission, superfluorescence, and lasing. The onset of lasing at high concentrations (above >1019 cm−3) in the case of pumping by high-energy photons occurs due to the high dephasing rates of quantum states resulting from a more rapid redistribution of vibrational energy.