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We report on the Czochralski crystal growth, polarized optical spectroscopy, and the first continuous-wave laser operation of 1.5 at.% Tm:LuVO 4 crystal on the 3 H 4 → 3 H 5 transition. The polarized absorption and stimulated-emission properties of Tm 3+ ions in LuVO 4 were revised and the crystal-field splitting of the Tm 3+ multiplets was determined by low-temperature (12 K) spectroscopy. The maximum stimulated-emission cross-section for the 3 H 4 → 3 H 5 transition is 2.48 × 10 -20 cm 2 at 2363 nm for π-polarization corresponding to an emission bandwidth of 28 nm. Evidence of phonon-assisted emissions of Tm 3+ ions above 2 µm is presented. The broadband emission properties of the Tm:LuVO 4 crystal make it promising for ultrashort pulse generation. Additionally, pumped by a 796 nm fiber-coupled laser diode, the Tm:LuVO 4 laser generated a Watt-level output power at 2279-2295 nm with a slope efficiency of 9.2% and linearly polarized emission (π-polarization).

The polarized spectral properties and ∼2.3 µm high-power continuous-wave laser operation of Tm 3+ -doped yttrium orthovanadate crystal (Tm:YVO 4 ) are reported. For the 3 H 4 → 3 H 5 transition, the stimulated-emission cross-section σ SE is 1.01 × 10 -20 cm 2 at 2276 nm corresponding to a large emission bandwidth of 52 nm (for π-polarization). Pumped by a 794 nm laser diode, the 1.5 at.% Tm:YVO 4 laser delivered 5.52 W at 2.29 µm with a slope efficiency of 19.9%, a laser threshold of 8.70 W, and a linear laser polarization (π). The Tm laser operated on the cascade scheme (on the 3 H 4 → 3 H 5 and 3 F 4 → 3 H 6 transitions) which was mainly responsible for the observed high laser slope efficiency. We also report on the first passively Q-switched Tm:YVO 4 laser at 2.3 µm by employing porous nano-grained cuprous selenide (PNG-Cu 2 Se) as a saturable absorber. The shortest pulse duration and the highest single pulse energy amounted to 706 ns and 3.65 µJ, respectively, corresponding to a pulse repetition rate of 62.8 kHz.

The laser diode (LD)-pumped efficient high-power cascade Tm:GdVO 4 laser simultaneously operating on the 3 F 4 → 3 H 6 (at ∼2 μm) and 3 H 4 → 3 H 5 (at ∼2.3 μm) Tm 3+ transition was first reported in this paper. The cascade Tm:GdVO 4 laser generated a maximum total continuous-wave (CW) laser output power of 8.42 W with a slope efficiency of 40%, out of which the maximum ∼2.3 μm CW laser output power was 2.88 W with a slope efficiency of 14%. To our knowledge, 2.88 W is the highest CW laser output power amongst the LD-CW-pumped ∼2.3 μm Tm 3+ -doped lasers reported so far.

The exceptional mechanical, electronic, topological, and optical properties, make bismuthene an ideal candidate for various applications in ultrafast saturation absorption and spintronics. Despite the extensive research efforts devoted to synthesizing this material, the introduction of defects, which can significantly affect its properties, remains a substantial obstacle. In this study, we investigate the transition dipole moment and joint density of states of bismuthene with/without single vacancy defect via energy band theory and interband transition theory. It is demonstrated that the existence of the single defect enhances the dipole transition and joint density of states at lower photon energies, ultimately resulting in an additional absorption peak in the absorption spectrum. Our results suggest that the manipulation of defects in bismuthene has enormous potential for improving the optoelectronic properties of this material.

We report on the cascade continuous-wave operation of a diode-pumped Tm:YVO 4 laser on the 3 F 4 → 3 H 6 (at ∼2 μm) and 3 H 4 → 3 H 5 (at ∼2.3 μm) Tm 3+ transitions. Pumped with a fiber-coupled spatially multimode 794 nm AlGaAs laser diode, the 1.5 at.% Tm:YVO 4 laser yielded a maximum total output power of 6.09 W with a slope efficiency of 35.7% out of which the 3 H 4 → 3 H 5 laser emission corresponded to 1.15 W at 2291-2295 and 2362-2371 nm with a slope efficiency of 7.9% and a laser threshold of 6.25 W.

In the present work, we report the structural properties of the two dimensional (2D) few-layered Ti 3 C 2 (OH) 2 /Ti 3 C 2 F 2 hybrid MXene synthesized via the HF acid etching method. Various characterizations were exploited to demonstrate the 2D layered structural properties of the hybrid MXene membranes. The density functional theory (DFT) simulation indicated the hybrid MXene possessed the small enough band gap, which could benefit the nonlinear optical applications in the infrared region. By the conventional open-aperture Z-scan technique, typical nonlinear saturable features were measured. Consequently, the hybrid MXene membranes exhibited the excellent saturable absorption properties at 1 and 1.3 µm. As a saturable absorber, passively Q-switched Nd:YVO 4 lasers with the prepared hybrid MXene membranes were realized at 1 and 1.3 µm, respectively, producing the stable Q-switching pulse train with a shortest duration of 130 ns.

The nonlinear absorption properties of GaAs were measured at 1.06 and 1.34 µm by the open aperture Z-scan technique in this paper. Based on a neodymium doped calcium niobium gallium garnet (Nd:CNGG) disordered crystal grown by the Czochralski method, passively Q-switched lasers with the conventional GaAs wafer as the saturable absorber were demonstrated, operating on the transitions of 4 F 3/2 → 2 I 11/2 and 4 F 3/2 → 2 I 13/2 . For the 4 F 3/2 → 2 I 11/2 transition, the laser operated at 1063 nm with a pulse duration of 546 ns and a repetition rate of 98.5 kHz. While for the 4 F 3/2 → 2 I 13/2 transition operating at 1340 nm, the minimum pulse width was 499.6 ns with the pulse repetition rate of 110.7 kHz.