Polycrystalline <scp> <scp>Ho:YAG</scp> </scp> Transparent Ceramics for Eye‐Safe Solid State Laser Applications

Abstract

High optical quality holmium doped yttrium aluminum garnet ( Ho:YAG ) transparent ceramics that contained 0.5–2.0 at.% holmium additives were fabricated by a reactive sintering method under vacuum. Fully dense Ho:YAG ceramics with the average grain size of ~10 μm were obtained after vacuum sintered at 1780°C for 8 h. The in‐line transmittances in the visible and infrared region are higher than 82% and 84%. The absorption coefficients of the 0.8, 1.0, 1.5, and 2.0 at.% Ho:YAG ceramics at 1907 nm was calculated to be 0.72, 0.89, 1.32, and 1.78 cm −1 , respectively. The absorption cross‐section of Ho:YAG ceramic was 0.645 × 10 −20 cm 2 . The 1.5 and 2.0 at.% Ho:YAG ceramic slabs were in‐band pumped by a Tm:fiber laser at 1907 nm. A maximum output power of 20.6 W at 2097 nm was obtained with a corresponding slope efficiency of 60.9%.