Transparent ceramics that large in size are promising materials for laser-based applications that usually require single crystals and glasses. Of all the transparent ceramics currently available, Nd-doped YAG ceramic was used to achieve the highest output power of a ceramic laser to date (105 KW). Therefore, transparent RE-doped CaF₂ ceramics are expected to resolve the problems encountered in the corresponding single-crystal structures.

However, the mechanical properties of the hot-formed ceramics were similar to that of the corresponding single crystals but inferior to that of hot-pressed CaF₂ ceramics. Meanwhile, there is no direct evidence that hot-formed CaF₂ ceramics have a polycrystalline structure.

To address this issue, the Key Laboratory of Materials for High Power Laser at Shanghai Institute of Optics and Fine Mechanics (SIOM), led by Prof. Long Zhang, has recently developed a new synthetic route and successfully fabricated transparent Nd-doped Ca_1？xY_xF_2+x ceramics via the ceramization of single crystals. The results of XRD measurements and transmission microscopy indicated that single-crystal Nd-doped Ca_1？xY_xF_2+x samples were successfully transformed into a polycrystalline ceramic.

The study was published in Materials & Design 

(http://www.sciencedirect.com/science/article/pii/S026412751631317X)

They examined the morphology, microstructural characteristics, optical properties, and laser performance of the ceramics. The broadband transmittance and emission spectra of the transparent Nd-doped Ca_1？xY_xF_2+x ceramic were analogous to those of the single-crystal samples, which suggests that the ceramic is particularly suitable for diode pumping and ultrashort laser pulses. The mechanical properties of the prepared Nd-doped Ca_1？xY_xF_2+x ceramics were superior to those of the single-crystal samples.

They obtained continuous-wave laser operation with an output power of 35 mW through the application of a fiber coupled laser diode with a central wavelength of approximately 808 nm. This suggests that the ceramics fabricated in this study are promising candidates for diode-pumped solid-state lasers and laser amplifiers.

Fig. 1. Photograph showing Nd-doped Ca1？xYxF2+x single crystals before and after the ceramization process.( Image by Jiang Yiguang)