Spectroscopy and 2.8†µm laser operation of disordered Er:CLNGG crystals.

We report on the first, to the best of our knowledge, laser operation on the 4I11/2 → 4I13/2 transition of erbium-doped disordered calcium lithium niobium gallium garnet (CLNGG) crystals with broadband mid-infrared emission properties. A 41.4 at.% Er:CLNGG continuous-wave laser generated 292 mW at 2.80 µm with 23.3% slope efficiency and a laser threshold of 209 mW. Er3+ ions in CLNGG feature inhomogeneously broadened spectral bands (σSE = 1.79 × 10-21 cm2 at 2.79 µm; emission bandwidth, 27.5 nm), a large luminescence branching ratio for the 4I11/2 → 4I13/2 transition of 17.9%, and a favorable ratio of the 4I11/2 and 4I13/2 lifetimes, exhibiting values of 0.34 ms and 1.17 ms (for 41.4 at.% Er3+), respectively.

Spectroscopy and diode-pumped laser operation of transparent Tm:Lu3Al5O12 ceramics produced by solid-state sintering.

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.

Spectroscopic properties and continuous-wave deep-red laser operation of Eu3+-doped LiYF4.

Eu3+-doped LiYF4 is reexamined as a laser material for the visible spectral region. Polarized absorption and emission cross sections as well as the fluorescence lifetime are determined. Branching ratios and radiative lifetime are calculated within the theory of 4f-4f transition intensities, which takes into account the influence of an excited configuration of the opposite parity 4fN-15d. Continuous-wave laser operation at 702 nm is demonstrated with a maximum output power of 15 mW and a slope efficiency of 4.6% under pumping with a frequency-doubled Ti:sapphire laser at 393.5 nm.