Optimization of Yb:CaF2 Transparent Ceramics by Air Pre-Sintering and Hot Isostatic Pressing

Year: 2024

Authors: Li X., Hu C., Guo LH., Wu JL., Toci G., Pirri A., Patrizi B., Vannini M., Liu Q., Hreniak D., Li J.

Autors Affiliation: Chinese Acad Sci, Transparent Ceram Res Ctr, Shanghai Inst Ceram, Shanghai 201899, Peoples R China; Jiangsu Univ, Sch Mat Sci & Engn, Zhenjiang 212013, Peoples R China; Univ Chinese Acad Sci, Ctr Mat Sci & Optoelect Engn, Beijing 100049, Peoples R China; CNR, CNR INO, Ist Nazl Ott, Via Madonna del Piano 10C, I-50019 Sesto Fiorentino, Fi, Italy; CNR, CNR IFAC, Ist Fis Applicata Carrara, Via Madonna del Piano 10C, I-50019 Sesto Fiorentino, Fi, Italy; Polish Acad Sci, Inst Low Temp & Struct Res, Okolna 2, PL-50422 Wroclaw, Poland.

Abstract: Yb:CaF2 transparent ceramics represent a promising laser gain medium for ultra-short lasers due to their characteristics: low phonon energy, relatively high thermal conductivity, negative thermo-optical coefficient, and low refractive index. Compared to single crystals, Yb:CaF2 ceramics offer superior mechanical properties, lower cost, and it is easier to obtain large-sized samples with proper shape and uniform Yb3+ doping at high concentrations. The combination of air pre-sintering and Hot Isostatic Pressing (HIP) emerges as a viable strategy for achieving high optical quality and fine-grained structure of ceramics at lower sintering temperatures. The properties of the powders used in ceramic fabrication critically influence both optical quality and laser performance of Yb:CaF2 ceramics. In this study, the 5 atomic percentage (at.%) Yb:CaF2 transparent ceramics were fabricated by air pre-sintering and hot isostatic pressing (HIP) using nano-powders synthesized through the co-precipitation method. The co-precipitated powders were optimized by studying air calcination temperature (from 350 to 550 degrees C). The influence of calcination temperature on the microstructure and laser performance of Yb:CaF2 ceramics was studied in detail. The 5 at.% Yb:CaF2 transparent ceramics air pre-sintered at 625 degrees C from powders air calcined at 400 degrees C and HIP post-treated at 600 degrees C exhibited the highest in-line transmittance of 91.5% at 1200 nm (3.0 mm thickness) and the best laser performance. Specifically, a maximum output power of 0.47 W with a maximum slope efficiency of 9.2% at 1029 nm under quasi-CW (QCW) pumping was measured.

Journal/Review: CERAMICS

Volume: 7 (3)      Pages from: 1053  to: 1065

More Information: This work was supported by the National Key R&D Program of China (Grant No. 2021YFE0104800), the International Partnership Program of Chinese Academy of Sciences (Grant No. 121631KYSB20200039), National Center for Research and Development (Contract No.WPC2/1/SCAPOL/2021), and the Chinese Academy of Sciences President’s International Fellowship Initiative (Grant No. 2024VEA0014).
KeyWords: Yb:CaF2 transparent ceramics; air pre-sintering; hot isostatic pressing; microstructure; laser performance
DOI: 10.3390/ceramics7030069