Ablation morphology affects the quality of laser processing. Therefore, the control of ablation morphology is very important. The influence of spot size combination mode on the ablation morphology of aluminum alloy is studied for the first time. Experimental results show that when the nanosecond laser spot is larger, the ablation morphology looks like a bowl-shape, and there is little solidification near the edge. When the nanosecond laser spot is smaller, the shape of the ablation morphology is similar to a hole, and the protuberance is formed near the edge of the cavity. Through the analysis and simulation of the physical model, the physical mechanism, which describes the influence of the spot size combination mode on the molten pool, is discussed. The research results of this paper have important guiding significance for the control of laser processing effect.

We adopt a compact intra-cavity pumped structure of Nd:YAG and Nd:YVO₄ crystals to develop an efficient dual-wavelength laser that operates at 946 nm and 1064 nm. A 808 nm laser diode is used to pump the Nd:YAG crystal, which emits at 946 nm, and the Nd:YVO₄ crystal, which emits at 1064 nm, is intra-cavity pumped at 946 nm. In order to avoid unnecessary pump light passing though the Nd:YAG crystal, reaching the Nd:YVO₄ crystal and having an impact on the cavity pump, the two crystals are placed as far from one another as possible in this experiment. The output power at 1064 nm can be adjusted from 1 W–2.9 W by varying the separation between the two crystals. A total output power of 4 W at the dual-wavelengths is achieved at an incident pump power of 30.5 W, where the individual output powers for the 946 nm and 1064 nm emissions are 1.1 W and 2.9 W, respectively.

In this paper, a multiple optical parametric oscillator based on MgO:APLN is reported. The polarization structure of MgO:APLN and output coupler transmittance are optimized, with a high repetition rate of 200 kHz and 1064 nm laser pumping. The 1.57 μm and 3.84 μm cross period parameters light output can be achieved by a single poled crystal for the first time. The maximum average output powers of 2.4 W at 1.57 μm and 1.31 W at 3.84 μm are obtained, corresponding to optical-optical conversion efficiency of 11.54% and 6.25%, respectively. For the phenomenon of energy back conversion appearing in the multiple optical parametric oscillation process, the numerical evolution of multi-wave coupling process through the coupled wave equations is investigated, and the concept of “back conversion in energy transmission area” is induced, and indicates that the existence of back conversion in energy transmission area causes the weak gain parameters of optical parametric oscillator to be enhanced twice. The theoretical analyses are basically in agreement with the experimental results.