Synthesis and Performance of Advanced Ceramic Lasers

TLDR

Recent advances in producing pore‑free polycrystalline Nd:YAG, Nd:YSAG, Yb:YSAG ceramics and Nd‑doped YAG single crystals via advanced ceramic processing. The study aims to show that advanced ceramic processing can enable high‑performance lasers with high efficiency, beam quality, and output energy. Pore‑free polycrystalline Nd‑ and Yb‑doped ceramics achieve laser conversion efficiencies comparable to commercial Nd:YAG single crystals, and a pore‑free Nd:YAG single crystal fabricated by solid‑state reaction exhibits slightly higher oscillation efficiency than polycrystalline ceramics; scattering is dominated by residual pores rather than grain boundaries, while heavily doped Nd:YAG single crystals can be produced by sintering and composite ceramics with complex structures can be fabricated without precise polishing or diffusion bonding.

Abstract

This paper reports recent progress in the production of polycrystalline Nd:YAG (Y 3 Al 5 O 12 ), Nd:YSAG (Y 3 Sc 1.0 Al 4.0 O 12 ), Yb:YSAG ceramics, and a Nd‐doped YAG single crystal with an almost perfect pore‐free structure by advanced ceramic processing. The laser conversion efficiency of pore‐free polycrystalline Nd‐ and Yb‐doped ceramics is extremely high, and their optical qualities are comparable with that of commercial high‐quality Nd:YAG single crystals. We have also succeeded in the fabrication of a Nd:YAG single crystal, which can be used for laser oscillation, by the solid‐state reaction method. Laser oscillation efficiency was very low when the pores remained inside the single crystal; however, the laser oscillation efficiency of the pore‐free Nd:YAG single crystal was slightly higher than that of polycrystalline Nd:YAG ceramics having high optical quality. From this fact, it was recognized that optical scattering occurs mainly in the residual pores inside the Nd:YAG ceramics and the scattering at the grain boundary is very less. In addition, we confirmed that a heavily doped Nd:YAG single crystal can be fabricated by the sintering method. Moreover, we have demonstrated the fabrication of a composite ceramic with complicated structures without the need for precise polishing and diffusion bonding. Advanced ceramic processing, which enables design flexibility of the laser element, presented in this work is important in the development of a high‐performance laser (high efficiency, high beam quality, and high output energy, etc.)