Laser polishing is widely employed to reduce the surface roughness of products with complex geometries. Traditional laser polishing techniques use a single high-power Gaussian beam to melt and smooth a thin layer of surface material. However, the reliance on high power lasers can present practical challenges such as minimizing surface evaporation or reducing overall cost. In this work, we combined two identical low-power laser beams with a spatial offset in between them to construct an elliptical beam. By changing the spatial offset, combined beams with different lengths along the major axis can be created. We observe over 20% improvement in line roughness reduction using this approach compared to a single Gaussian laser beam with the same total power. Additionally, both experiment and simulation results suggest such improvement is because this dual-laser set-up can create a longer molten pool compared to a single laser.
In this letter, we investigated random lasing phenomenon in ZnO powder using the pump_probe technique. Under 267nm laser pumping, supernarrow single_mode emission and multi_mode emission were observed by precisely controlling the pumping intensity and the excitation beam size on the sample. The supernarrow emission peaks are much narrower than the normal luminescence and ASE spectra. The time_resolved pump_probe measurement shows that the lifetime of the emission state above the lasing threshold is only a few picoseconds which demonstrates that the formation of supernarrow random lasing bandwidth is due to stimulated emission.
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