Fabrication of sub-micrometer sized Er:CaF2 transparent ceramics for eye-safe lasers

Abstract

The 1 at.% Er:CaF2 transparent ceramics were prepared by the air pre-sintering and hot isostatic pressing (HIP) using nano-powders synthesized by the co-precipitation method. The influence of pre-sintering temperature and HIP post-treatment on the density, microstructures, optical and photoluminescence properties of Er:CaF2 ceramics were investigated. After HIP post-treatment (650 °C × 2 h, 100 MPa Ar), the pores in the pre-sintering ceramics were gradually eliminated and high transparency was achieved. The maximum in-line transmittance of the HIPed 1 at.% Er:CaF2 reaches 90.5% at 1600 nm (2.8 mm thickness) when the pre-sintered temperature is 625 °C.The absorption cross section was calculated. The strong absorption peak at 1530 nm reveals an unfavorable infrared emission. The main emission peak at 1530 nm, which is derived from the 4I13/2 → 4I15/2 transition of Er3+, can be observed under excitation of 980 nm. Owing to the long lifetime of 4I13/2 (32.3 ms) and large emission cross section, the 1 at.% Er:CaF2 transparent ceramics have great potential to achieve a good NIR laser performance in the 1.5 μm region.