Growth and spectral properties of Ho3+ doped α-NaYF4 single crystal

Abstract

Ho3+ doped α-NaYF4 single crystal with size of ∼∅10mm×100mm was grown by an improved Bridgman method using KF as flux with the molar composition of raw materials NaF: KF: YF3: HoF3=30: 18: 51: 1. The X-ray powder diffraction, transmission spectrum from 2500nm to 8000nm, absorption spectrum, emission spectrum by 640nm excitation and fluorescence decay curves at 1190nm and 2040nm of the obtained single crystal were detected. The Judd–Oflet theory was applied to calculate the Judd–Oflet intensity parameters Ω2,4,6, radiative transition rate, branching ratio, radiative lifetime according to its measured absorption spectrum. The calculated maximum emission cross section by McCumber theory of Ho3+ doped α-NaYF4 crystal for ∼1.2μm and ∼2.0μm reached 0.42×10−20cm2 and 0.69×10−20cm2, respectively. The gain cross section spectra were calculated based on the absorption and emission cross section spectra. In the meantime, the fluorescent lifetime at 1190nm and 2040nm were also estimated to be 3.21ms and 18.12ms from their decay curves. The Ho3+ doped α-NaYF4 single crystal with ∼90% high transmittance in wide range of 300–8000nm and long lifetime of fluorescence may be considered as a potential candidate for applications in mid-infrared optical devices.