Peixiong Zhang

Passively Q-switched dual-wavelength green laser with an Yb:YAG/Cr^4+:YAG/YAG composite crystal

A compact dual-wavelength passively Q-switched green laser by intra-cavity frequency doubling of a Yb:YAG/Cr4+:YAG/YAG composite crystal was demonstrated for the first time to our best knowledge. The maximum green laser output power of 1.0 W was obtained under the pump power of 9.7 W, and the corresponding slope efficiency is 15.2%. The shortest pulse width, largest pulse energy, and highest peak power were achieved to be 5.54 ns, 246.1μJ, and 40.76 KW, respectively. Dual-wavelength laser oscillation simultaneously at 515 nm and 524.5 nm has been achieved. This passively Q-switched dual-wavelength green laser can be used as a laser source for Terahertz generation.

Enhanced 2.7 μm mid-infrared emissions of Er 3+ via Pr 3+ deactivation and Yb 3+ sensitization in LiNbO 3 crystal

The use of Pr³⁺ codoping for enhancement of the transition of Er³⁺: ⁴I_11/2 → ⁴I_13/2 2.7 μm emissions was investigated in the Er/Yb codoped LiNbO₃ crystal for the first time. It is found that the codoped of Pr³⁺ ion in Er³⁺, Yb³⁺ and Pr³⁺ triply doped LiNbO₃ crystal (Er/Yb/Pr: LN) greatly enhances Er³⁺: 2.7 μm emission under excitation of a common 970 nm laser diode, depopulates the lower laser level of Er³⁺:⁴I_13/2, and has little influence on the higher laser level of Er³⁺:⁴I_11/2 at the same time for population inversion. The 2.7 μm emission characteristics and energy transfer were investigated in detail. The energy transition efficiency from lower laser level of Er³⁺:⁴I_13/2 to Pr³⁺:³F₄ level is as high as 0.42, indicating that the Pr³⁺ ion is an effective deactivation ion for Er³⁺ ion in LiNbO₃ crystal. These results suggest that Er/Yb/Pr: LiNbO₃ crystal may become an attractive host for developing solid state lasers at around 2.7 μm under a conventional 970 nm LD pump.

Directional release of the stored ultrashort light pulses from a tunable Bragg-grating microcavity

We demonstrate numerically the ability for directionally releasing the stored ultrashort light pulse from a microcavity by means of two-pulse nonlinear interaction in a cascading Bragg grating structure. The setting is built by a chirped grating segment which is linked through a uniform segment, including a tunable microcavity located at the junction between the two components. Our simulations show that stable trapping of an ultrashort light pulse can be achieved in the setting. The stored light pulse in a microcavity can be possibly released, by nonlinearly interacting with the lateral incident control pulse. Importantly, by breaking the symmetry of potential cavity, the stably trapped light pulse can be successfully released from the microcavity to the expected direction. Owing to the induced optical nonlinearity, the released ultrashort light pulses could preserve their shapes, propagating in a form of Bragg grating solitons through the uniform component, which is in contrast to the extensively studied light pulse trappings in photonic crystal cavities which operate at the linear regime.

Enhanced 573 nm yellow emissions of Dy^3+ via Tb^3+ deactivation in Na_2Gd_4(MoO_4)_7 crystal

A Dy3+/Tb3+ co-doped Na2Gd4(MoO4)7 yellow laser crystal was successfully grown and analyzed. The use of Tb3+ codoping for enhancing the Dy3+:4F9/2→6H13/2 yellow emissions was investigated in the Na2Gd4(MoO4)7 crystal for the first time. In comparison to Dy3+ single-doped Na2Gd4(MoO4)7 crystal, the Dy3+/Tb3+ co-doped Na2Gd4(MoO4)7 crystal possessed a higher fluorescence branching ratio (80.2%), transition probability (3704 s−1), and fluorescence emission cross section (1.34×10−20 cm2) corresponding to the laser transition 4F9/2→6H13/2 of Dy3+. It was found that the introduced Tb3+ enhanced the 573 nm emission by depopulating the population of the laser lower level Dy3+: 6H13/2, and has little influence on the laser upper level Dy3+: 4F9/2 at the same time. These results suggest that Dy3+/Tb3+ co-doped Na2Gd4(MoO4)7 crystal may be an attractive host for developing solid state lasers at around 573 nm under a conventional 450 nm LD.