Synthesis of Yb: YAG Ceramics Without Sintering Additives and their Performance

High‐quality 10%Yb: YAG ceramics was successfully synthesized without sintering additives such as SiO 2 for the first time. Optical scattering loss of the Yb: YAG ceramics was 0.1%/cm and its transmitted wavefront distortion was λ/19.5 ( t = 4.7 mm), which was very comparable to single crystal laser materials. Laser performance of thin disk made of this material (φ11 × t 0.15 mm) was 74.1% of slope efficiency (optical‐to‐optical conversion efficiency: 68.1%) and the maximum output power reached 1.8 kW. Synthesis of high‐purity and high‐quality YAG ceramics without using sintering additives was demonstrated for the first time to our knowledge and we can discuss the technological meaning of high‐purity materials for the future.