Spectroscopy, Continuous-Wave and Passively Q-Switched Laser Operation of Transparent Tm:LuAG Ceramics

Summary form only given. Transparent ceramics are promising materials for solid-state lasers because of their size-scalable synthesis method, high optical quality and similar spectroscopic properties as compared to their single-crystal counterparts. In particular, the Lu
₃
Al
₅
O
₁₂
(LuAG) garnet is attractive for the fabrication of transparent ceramics due to its excellent thermal properties [1]. Due to the closeness of ionic radii of Lu
³⁺
and Tm
³⁺
, LuAG ceramic is attractive for hosting tulium (Tm
³⁺
) ions which are known for its eye-safe laser emission at ~2 μm (the
³
F
₄
→
³
H
₆
transition). Moreover, in garnets, the Tm
³⁺
emission typically occurs above 2 μm which is relevant to mode-locking of femtosecond lasers [2]. Here, we report on the synthesis, spectroscopy, efficient continuous-wave (CW) and passively Q-switched (PQS) laser operation of Tm:LuAG transparent ceramics. They were fabricated by solid-state reactive sintering at 1830 °C of Lu
₂
O
₃
, α-Al
₂
O
₃
and Tm
₂
O
₃
powders, with MgO and TEOS as sintering aids. A SEM image of the ceramic fractured surface shows clear grain boundaries and uniform grain size distribution (mean size: 21 μm), Fig. 1(a). The absorption, and stimulated-emission (SE), USE, cross -sections for the
³
H
₆
↔
³
F
₄
transition are shown in Fig. 1(b). In the long wavelength part of the SE spectrum, USE = 0.11 x10
²⁰
cm
²
at 2021 nm. The measured lifetime of the
³
F
₄
state num is 9.68 ms, Fig. 2(c). The transition intensities for Tm
³⁺
were also determined within the Judd-Ofelt theory