Infrared-to-visible upconversion in Nd3+-doped chalcohalide glasses -: art. no. 144101

The infrared to visible upconversion processes have been investigated for Nd3+-doped chalcohalide glasses with different halide modifiers by using steady-state and time-resolved laser spectroscopy. Two different upconversion mechanisms have been identified depending on the infrared excitation wavelength. When the excitation wavelength is resonant with the F-4(3/2) state, three main bands at 538, 600, and 675 nm are observed and attributed to emissions from the (4)G(7/2) level. These upconverted emissions occur via energy-transfer upconversion involving two neodymium ions in the F-4(3/2) state. However, nonresonant excitation at higher energies than that of F-4(3/2) state (between states F-4(3/2) and F-4(5/2))or in resonance with the F-4(5/2) state, causes an additional blue emission to originate from the P-2(1/2) state. This latter upconverted emission can be attributed to excited-state absorption of the pump radiation. The proposed upconversion mechanisms responsible for the different emissions from levels P-2(1/2) and (4)G(7/2) are supported by both the time evolution of the upconversion luminescence after infrared pulsed excitation and the upconversion luminescence excitation spectra.