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

•Ho3+ doped α-NaYF4 single crystal was grown successfully by an improved Bridgman method.•The transmission spectrum presented a wide region from 2500 nm to 8000 nm for Ho3+ doped α-NaYF4 single crystal.•The crystal exhibited a broad emission band at 2.0 μm from 1850 nm to 2150 nm.•The long fluorescence lifetime for the 5I7 multiplet was measured to be 18.12 ms.

Ho3+ doped α-NaYF4 single crystal with size of ∼∅10 mm × 100 mm 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 2500 nm to 8000 nm, absorption spectrum, emission spectrum by 640 nm excitation and fluorescence decay curves at 1190 nm and 2040 nm 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 ∼1.2 μm and ∼2.0 μm reached 0.42 × 10−20 cm2 and 0.69 × 10−20 cm2, respectively. The gain cross section spectra were calculated based on the absorption and emission cross section spectra. In the meantime, the fluorescent lifetime at 1190 nm and 2040 nm were also estimated to be 3.21 ms and 18.12 ms from their decay curves. The Ho3+ doped α-NaYF4 single crystal with ∼90% high transmittance in wide range of 300–8000 nm and long lifetime of fluorescence may be considered as a potential candidate for applications in mid-infrared optical devices.