Distinguishing the effects of lattice Gd3+ and segregated Gd3+ on optical properties of Yb:GdYAG transparent ceramics

Whether adding Gd 3+ in Yb:GdYAG broadens absorption and emission peaks for better laser performance is recently under debate. By preparing (Yb 0.05 Y 0.95-x Gd x ) 3 Al 5 O 12 (x = 0.2, 0.6, 1, 5, 10, 20 at%) transparent ceramics with one-step solid-state reactive sintering under vacuum, we report a non-monotonic relation between increasing Gd 3+ content and micro-structure/properties. Specifically, the grain size decreases till x = 10 at%, but increases at 20 at% with secondary phases formed at grain boundaries by segregated Gd 3+ . The optimal optical properties are achieved at 10 at%. The in-line transmittance reaches 83.9 % at 1100 nm. Absorption and emission cross-sections are significantly broadened (8.0 × 10 −21 cm 2 at 940 nm and 26.7 × 10 −21 cm 2 at 1030 nm, respectively). The FWHM of main emission peak at 1030 nm receives a ∼60 % extension to 15.2±0.4 nm. It indicates lattice Gd 3+ broadens peak widths and improves transparency, while segregated Gd 3+ diminishes peak broadening and adversely affects transparency.