2022, Zhang, Ning, Liu, Shande, Wang, Zhanxin, Liu, Jian, Xu, Xiaodong, Xu, Jun, Wang, Jun, Liu, Peng, Ma, Jie, Shen, Deyuan, Tang, Dingyuan, Lin, Hui, Zhang, Jian, Chen, Weidong, Zhao, Yongguang, Griebner, Uwe, Petrov, Valentin

We demonstrate a widely tunable and passively mode-locked Tm:Y2O3 ceramic laser in-band pumped by a 1627-nm Raman fiber laser. A tuning range of 318 nm, from 1833 to 2151 nm, is obtained in the continuous-wave regime. The SESAM mode-locked laser produces Fourier-transform-limited pulses as short as 75 fs at ∼ 2.06 µm with an average output power of 0.26 W at 86.3 MHz. For longer pulse durations of 178 fs, an average power of 0.59 W is achieved with a laser efficiency of 29%. This is, to the best of our knowledge, the first mode-locked Tm:Y2O3 laser in the femtosecond regime. The spectroscopic properties and laser performance confirm that Tm:Y2O3 transparent ceramics are a promising gain material for ultrafast lasers at 2 µm.

2022, Eremeev, Kirill, Loiko, Pavel, Braud, Alain, Camy, Patrice, Zhang, Jian, Xu, Xiaodong, Zhao, Yongguang, Liu, Peng, Balabanov, Stanislav, Dunina, Elena, Kornienko, Alexey, Fomicheva, Liudmila, Mateos, Xavier, Griebner, Uwe, Petrov, Valentin, Wang, Li, Chen, Weidong

We report on a detailed spectroscopic study of a Tm3+-doped transparent sesquioxide ceramic based on a solid-solution (lutetia – yttria, LuYO3) composition. The ceramic was fabricated using commercial oxide powders by hot isostatic pressing at 1600°C for 3 h at 190 MPa argon pressure. The most intense Raman peak in Tm:LuYO3 at 385.4 cm−1 takes an intermediate position between those for the parent compounds and is notably broadened (linewidth: 12.8 cm−1). The transition intensities of Tm3+ ions were calculated using the Judd-Ofelt theory; the intensity parameters are W2 = 2.537, W4 = 1.156 and W6 = 0.939 [1020 cm2]. For the 3F4 → 3H6 transition, the stimulated-emission cross-section amounts to 0.27 × 10−20 cm2 at 2059nm and the reabsorption-free luminescence lifetime is 3.47 ms (the 3F4 radiative lifetime is 3.85 ± 0.1 ms). The Tm3+ ions in the ceramic exhibit long-wave multiphonon-assisted emission extending up to at least 2.35 µm; a phonon sideband at 2.23 µm is observed and explained by coupling between electronic transitions and the dominant Raman mode of the sesquioxides. Low temperature (12 K) spectroscopy reveals a significant inhomogeneous spectral broadening confirming formation of a substitutional solid-solution. The mixed ceramic is promising for ultrashort pulse generation at >2 µm.