As a commonly used structural material, the separation quality of thick glass has always been concerned. The current mechanical cutting methods used for thick glass not only are inefficient but also require subsequent polishing. A laser three-focus scheme (LTFS) was proposed in this paper to achieve high-quality and efficient separation. A confirmatory experiment and optical simulations have been carried out to confirm the correctness of the scheme. A finite element simulation model for LTFS separating low-iron glass was established, which analyzes the temperature and stress distributions. The fracture mechanism of glass was revealed by combining the crack morphology and thermal stress distribution. The experimental results demonstrate that the LTFS can perform high-quality separation of low-iron glass with a thickness of 20 mm, the width of kerfs is less than 25 µm, and the rms roughness is less than 5.5 nm. The separated sidewall is smooth and flat, without any unexpected defects, such as damage and cracks, and the subsequent polishing is not required.
