Blue and green upconversion emissions of Zr:Nd:LiNbO3 single crystals

Abstract

Zr:Nd:LiNbO3 crystals codoped with 0.1 mol% of Nd2 O3 and three concentrations of ZrO2 (0, 2 and 4 mol%) were grown by the Czochralski method from the congruent melt. The X-ray diffraction (XRD) patterns, UV–visible absorption and infrared (IR) spectra were measured to analyze the crystal composition and defect structure. The blue and green upconversion emissions of Nd3+ ions under 598 nm excitation were observed. The intensity of upconversion emissions was increased by the introduction of 2 mol% zirconium ion (Zr4+) and decreased by the introduction of 4 mol% Zr4+ ions. The luminescence decay measurement indicated that the 4G7/2 state of Nd3+ ion was mainly populated by excited state absorption process. It was proposed that Nd:LiNbO3 crystals doped with approximately 2 mol% Zr4+ ions could be applied as laser materials at 522/535 nm.