Laser etching technique using bubble jet impact for glass substrates

The purpose of this paper is to propose a new laser etching technique using bubble jet impact for glass substrates. An Nd:YAG laser is applied to the backside of the substrate which is partially submerged in water. A metal plate is placed below the glass substrate. The metal vaporizes the water and generates a turbulent bubble flow. The bubble nozzle is proposed to enhance the impact of the bubble jet. The glass surface will first be softened, and then expelled by the shock wave resulting from the jet impact. The phenomena of bubble nucleation, growth, collapse, and jet impact were studied in this paper. The formation of the etching cavity can be divided into three types: double-petal, triple-petal, and four-petal. The etching pits expanded and combined to form a complete cavity. The needed laser power does not exceed 5 W. The proposed laser etching method was successfully demonstrated for etching a cavity of 5–20 µm in depth and 50–250 µm in diameter. The bubble jet of the small nozzle diameter is well concentrated, creating a strong jet impact on the glass surface. A greater nozzle depth can enhance the impact of the bubble jet. The proposed etching technique has great potential to provide an improved solution for the micro-machining of glass.