Влияние концентрации фосфатов на спектральные свойства ионов тулия во фторфосфатных стеклах

The Jadd-Ofelt parameters for thulium ions in fluorophosphate glasses with different phosphate content are calculated. The proximity of the values of the parameters Ωt of glasses with a content of up to 10 mol% Ba(PO3)2 to the similar parameters of the fluoride glasses and a sharp increase in their values with a further increase in phosphates are shown. In the framework of the Jadd-Ofelt theory, the spectral-luminescent parameters of glasses are analyzed. The spontaneous transitions probabilities, branching coefficients (β), and radiation lifetimes (τrad) for various excited states of Tm3+ ions are obtained. It was found that, at low phosphate concentrations, glasses have a high radiation lifetime for the excited 3F4 laser level. It has been shown that the glasses with a content of up to 10 mol% Ba(PO3)2 are characterized by a wide flat gain spectrum, which makes them promising materials for creating broadband amplifiers.

Роль модельных представлений в описании кинетики люминесценции гибридных нитевидных нанокристаллов

On the example of InP/InAsP/InP nanowires, the role of theoretical models in the photodynamics study of hybrid semiconductor structures is considered. The photodynamics of luminescence of an array of InP/InAsP/InP nanowires formed by molecular beam epitaxy on a Si (III) substrate was studied. Based on a comparison of several kinetic models, including the use of poly-exponential and stretched-exponential functions, the analysis of experimental data is carried out. Experiments were performed by excitation with laser radiation of 633 nm at room temperature. It has been shown that the luminescence decay kinetics of the InAsP nanoinsert is best described in terms of the contact quenching model. The total decay time of the excited state (radiation lifetime) of the InAsP insert was estimated at τ ~ 40 ns. The reasons for the unusually long duration of transfer of excitation from InP have been suggested.

Photoluminescence from Suspended and Supported Graphene

The thermal conductivity of suspended graphene varies greatly under light, but the thermal conductivity of supported graphene does not change as much as that of suspended graphene. This is due to the fact that all of the loaded graphene is placed on the substrate and the thermal diffusivity of the loaded graphene is very good. In this paper, the ultrafast properties of supported graphene and suspended graphene have been studied. Suspended graphene has unique thermal conductivity, and its thermal conductivity will change greatly with the increase of temperature. Because of graphene has no band gap, the photon emission of supported graphene cannot be realized by electron hole recombination as in direct band gap materials. Optical emission of hot carriers is possible in graphene, but usually inefficient. That’s because most materials have much faster thermal carrier relaxation time than radiation lifetime. Herein, the hot carrier emission of suspended graphene and supported graphene are studied by femtosecond laser. It is found that the hot carrier can reduce the relaxation time of hot carrier in suspended structure. The suspension structure does increase the intensity of photon emission.