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- ItemDiode-pumped sub-50-fs Kerr-lens mode-locked Yb:GdYCOB laser(Washington, DC : Soc., 2021) Zeng, Huangjun; Lin, Haifeng; Lin, Zhanglang; Zhang, Lizhen; Lin, Zhoubin; Zhang, Ge; Petrov, Valentin; Loiko, Pavel; Mateos, Xavier; Wang, Li; Chen, WeidongWe present a sub-50-fs diode-pumped Kerr-lens mode-locked laser employing a novel “mixed” monoclinic Yb:Ca4(Gd,Y)O(BO3)3 (Yb:GdYCOB) crystal as a gain medium. Nearly Fourier-limited pulses as short as 43 fs at 1036.7 nm are generated with an average power of 84 mW corresponding to a pulse repetition rate of ∼70.8 MHz. A higher average power of 300 mW was achieved at the expense of the pulse duration (113 fs) corresponding to an optical-to-optical efficiency of 35.8% representing a record-high value for any Yb-doped borate crystal. Non-phase-matched self-frequency doubling is observed in the mode-locked regime with pronounced strong spectral fringes which originate from two delayed green replicas of the fundamental femtosecond pulses in the time domain.
- ItemTm3+-doped calcium lithium tantalum gallium garnet (Tm:CLTGG): novel laser crystal(Washington, DC : OSA, 2021) Alles, Adrian; Pan, Zhongben; Loiko, Pavel; Serres, Josep Maria; Slimi, Sami; Yingming, Shawuti; Tang, Kaiyang; Wang, Yicheng; Zhao, Yongguang; Dunina, Elena; Kornienko, Alexey; Camy, Patrice; Chen, Weidong; Wang, Li; Griebner, Uwe; Petrov, Valentin; Solé, Rosa Maria; Aguiló, Magdalena; Díaz, Francesc; Mateos, XavierWe report on the development of a novel laser crystal with broadband emission properties at ∼2 µm – a Tm3+,Li+-codoped calcium tantalum gallium garnet (Tm:CLTGG). The crystal is grown by the Czochralski method. Its structure (cubic, sp. gr. 𝐼𝑎3¯𝑑, a = 12.5158(0) Å) is refined by the Rietveld method. Tm:CLTGG exhibits a relatively high thermal conductivity of 4.33 Wm-1K-1. Raman spectroscopy confirms a weak concentration of vacancies due to the charge compensation provided by Li+ codoping. The transition probabilities of Tm3+ ions are determined using the modified Judd-Ofelt theory yielding the intensity parameters Ω2 = 5.185, Ω4 = 0.650, Ω6 = 1.068 [10−20 cm2] and α = 0.171 [10−4 cm]. The crystal-field splitting of the Tm3+ multiplets is revealed at 10 K. The first diode-pumped Tm:CLTGG laser generates 1.08 W at ∼2 µm with a slope efficiency of 23.8%. The Tm3+ ions in CLTGG exhibit significant inhomogeneous spectral broadening due to the structure disorder (a random distribution of Ta5+ and Ga3+ cations over octahedral and tetrahedral lattice sites) leading to smooth and broad gain profiles (bandwidth: 130 nm) extending well above 2 µm and rendering Tm:CLTGG suitable for femtosecond pulse generation.