Long persistent luminescence in Mn 2+ -activated sodium gallium germanate glass and glass ceramics induced by infrared femtosecond laser pulses

A distinct long persistent luminescence (LPL) was obtained from home-made Mn2+-activated sodium gallium germanate glass samples which were excited by an infrared femtosecond laser. The LPL, with a central wavelength longer than 600 nm, can be seen by the naked eye for more than one hour in the dark at room temperature. It has been proven that the LPL originated from the T-4(1) -> (6)A(1) transition of Mn2+ ions rather than from femtosecond laser induced extrinsic defects with photoluminescence (PL) bands peaking at 1.85 and 2.2 eV. The LPL properties of Mn2+ in the same host glass-ceramics were also investigated. An obvious green emission band appeared in PL spectra while absent in LPL spectra, which indicated a process distinguished from traditional heat-assisted tunneling effect. A new mechanism based on the process of strong-field excitation, collision excitation, electron trapping and direct capture of de-trapped electrons by excited states of Mn2+ ions is proposed to elucidate the generation of LPL. (C)2016 Optical Society of America