Upconversion emissions of the NaMgF₃: Tm³⁺, Yb³⁺ submicron particles and the emission modulation by the Mn²⁺ ions in the visible range

With the excitation of a 978 nm laser, upconversion emission of the NaMgF₃: Tm³⁺, Yb³⁺, Mn²⁺ submicron particles include two red emission bands located at 648 and 698 nm and a green emission at about 510 nm in the visible range. The experimental results confirm that the Mn²⁺ ions play the key role in the emission modulation between the 648 nm and 698 nm. The incident laser power dependence confirms that the emission at 648 nm is completely different from the emissions at 698 nm, and more than 3 photons are involved in the emission at 648 nm. With the doping of Mn²⁺ ions, the intensity ratio R₁/R₂ of the emission at 648 nm and 698 nm increases first, and decreases for the Mn²⁺ concentration larger than 2%. The incident laser power and laser pulse-width also have evident modulation effect of the UC emissions. All the Mn²⁺ related phenomena are due to the energy transfer paths ET5 and ET6 between the Tm³⁺ and Mn²⁺ ions.