Ultra-broadband near-infrared luminescence of ordered–disordered multi-sited Cr3+ in La3Ga5.5Nb0.5O14:Cr3+

Abstract

Ultra-broadband near-infrared (NIR) 600–1300 nm emission composed of two peaks centered at 730 nm and 1030 nm can be achieved in La₃Ga_5.5Nb_0.5O₁₄ (LGNO):Cr³⁺, which are probably due to ⁴T₂ → ⁴A₂ transition of Cr³⁺ ions at disordered octahedral site (site I) and ordered tetrahedral site (site II), respectively. The site occupation of Cr³⁺ is deduced according to crystal field theory combined with crystal structure, steady and time-resolved photoluminescence (PL) spectra, Raman spectra and Electron Paramagnetic Resonance (EPR) spectra. The ordered–disordered structure characterized by Raman spectra has distinct influence on photoluminescence behavior of these two peaks such as temperature dependence of peak positions and intensities. Cr³⁺ at disordered octahedral site with the ∼730 nm emission peak and a longer decay time experiences a stronger crystal field and is more easily influenced by ordered–disordered structure than the one in ordered tetrahedral site. The research may open a perspective to design NIR tunable lasers.