Rare earth (RE)-doped phosphate glasses have proven to be the
attractive materials for the development of fiber lasers because they
possess the advantages such as high luminescence efficiency and lack of
thermal lensing effects. Compared to silica glasses, phosphate glasses
offer distinctive optical properties such as large infrared transmission
window, good chemical durability, high gain density, wide bandwidth
emission spectrum and low up-conversion characteristics [1]. The high
gain density in phosphate glass is due to high solubility for RE ionswhich
allows large concentrations of active ions to be introduced into a
relatively small volume. The high ion density results in a significantly
smaller optical gain device that can be fabricated out of silica-based
glasses traditionally used for fibers [2].
Among the RE ions, trivalent europium (Eu3+ (4f6)), is an efficient
fluorescing activator in the orange-red region because Eu3+ ions emit
narrow band and almost monochromatic light and have long lifetimes of
the excited states. Eu2O3-doped phosphors are commonly used in field
emission technology and LEDs, which exhibit higher luminescence
efficiency compared with other luminous materials [3–14]. Also Eu3+
ions have been widely used both in crystalline and glassy materials to
probe the local environment around the RE ions because, its optical
transitions are very sensitive to the local surroundings and one of its
transition, 5D0↔7F0, is a singlet and non-degenerate under any symmetry
[15]. Hence, the information regarding the local environment around the
Eu3+ ion depends only on the splitting of the 5D0→7FJ emission spectra.
Depending on the number of Stark components into which the 5D0→7FJ
emission transitions split, the symmetry at the Eu3+ ion site can be
predicted by the crystal-field (CF) parameterization [15–17].
In view of above research and technological importance, the
Eu2O3-doped P2O5+K2O+KF+MO+Al2O3 (M=Mg, Sr and Ba)
glasses have been prepared and investigated. The energy level scheme
of Eu3+ ions in these glasses has been evaluated by means of a
parametric free-ion and CF Hamiltonian models. The phenomenological
Judd-Ofelt (JO) parameters (Ωλ, λ=2, 4 and 6) have been
determined and are used to predict the radiative properties of the
excited levels of Eu3+ ions. The relative intensity ratio of 5D0→7F2 to
5D0→7F1 transitions has been evaluated to estimate the asymmetry of
the local CF around the Eu3+ ions. The results obtained in the present
work are compared with those reported Eu2O3-doped glass systems.