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 4F3/2 state, three main bands at 538, 600, and 675 nm are observed and attributed to emissions from the 4G7/2 level. These upconverted emissions occur via energy-transfer upconversion involving two neodymium ions in the 4F3/2 state. However, nonresonant excitation at higher energies than that of 4F3/2 state (between states 4F3/2 and 4F5/2) or in resonance with the 4F5/2 state, causes an additional blue emission to originate from the 2P1/2 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 2P1/2 and 4G7/2 are supported by both the time evolution of the upconversion luminescence after infrared pulsed excitation and the upconversion luminescence excitation spectra.

This work has been supported by the Ministerio de Ciencia y Tecnologia Ref. BFM2000-0352 and French-Spanish PICASSO Program No. HF 99/43 and Basque Country University Ref. G21/98.

Peer reviewed