Abstract
A transparent Tm:Lu3Al5O12 ceramic is fabricated by solid-state reactive sintering at 1830 °C for 30 h using commercial α-Al2O3 and Lu2O3/Tm2O3 powders and sintering aids - MgO and TEOS. The ceramic belongs to the cubic system and exhibits a close-packed structure (mean grain size: 21 µm). The in-line transmission at ∼1 µm is 82.6%, close to the theoretical limit. The spectroscopic properties of the ceramic are studied in detail. The maximum stimulated-emission cross-section is 2.37×10-21 cm2 at 1749nm and the radiative lifetime of the 3F4 state is about 10 ms. The modified Judd-Ofelt theory accounting for configuration interaction is applied to determine the transition probabilities of Tm3+, yielding the intensity parameters Ω2 = 2.507, Ω4 = 1.236, Ω6 = 1.340 [10-20 cm2] and α = 0.196×10-4 cm. The effect of excited configurations on lower-lying interconnected states with the same J quantum number is discussed. First laser operation is achieved under diode-pumping at 792 nm. A 4 at.% Tm:Lu3Al5O12 ceramic laser generated 3.12 W at 2022-2035nm with a slope efficiency of 60.2%. The ceramic is promising for multi-watt lasers at >2 µm.
Highlights
Transparent ceramics doped with rare-earth ions (RE3+) represent a promising alternative to the single-crystal development for laser applications [1,2,3]
We demonstrate the potential of Tm:Lu3Al5O12 transparent ceramics for highly-efficient multi-watt laser operation at ~2 μm and study thoroughly their spectroscopic properties, which are of key importance for the development of CW and in particular ML lasers
We demonstrated efficient laser operation of a Tm:Lu3Al5O12 transparent ceramic
Summary
Transparent ceramics doped with rare-earth ions (RE3+) represent a promising alternative to the single-crystal development for laser applications [1,2,3]. Tm3+-doped garnets are known for long upper laser level lifetimes (~10 ms) and emission wavelengths extending beyond 2 μm [13], where the unwanted structured absorption of water in the atmosphere is absent The latter is in particular relevant for mode-locked (ML) lasers operating at ultrashort pulse durations (broad spectra) with specific applications [14]. Gluth et al demonstrated a Tm:Y3Al5O12 ceramic oscillator ML by a GaSb-based SEmiconductor Saturable Absorber Mirror (SESAM) delivering 3-ps pulses at 2012 nm at a repetition rate of 89 MHz [18] Another compound in the cubic garnet family, i.e., lutetium aluminum garnet, Lu3Al5O12, is known for its better thermal properties as compared to its yttrium counterpart which is advantageous for the ceramic technology [19,20]. We demonstrate the potential of Tm:Lu3Al5O12 transparent ceramics for highly-efficient multi-watt laser operation at ~2 μm and study thoroughly their spectroscopic properties, which are of key importance for the development of CW and in particular ML lasers
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