Enhanced Bessel beam generation with flat-top beams for precision laser cutting in optical glass

A Gaussian beam is often used as the source for Bessel beam generation; however, its Gaussian intensity profile results in a tapered edge along the propagation direction. To address this issue, a flat-top beam is employed to generate a uniform intensity profile, theoretically achieving an ideal working distance in non-diffracting zones. The flat-top beam is shaped from a point light source, expanded by a convex lens, and then homogenized by an aspherical lens to achieve a flat-top beam with an evenness rate of 93%. The achievement of a long working distance has been demonstrated through simulations and experiments. Simulation results indicate that, for the same beam width, the flat-top beam generates a 33% longer working distance compared to a Gaussian beam and exhibits a “steep edge” along the propagation axis. Experimentally, the method extended the application to a remarkable 2.4mm, compared to a Gaussian-generated Bessel beam with a full width at half maximum (FWHM) of about 1.8mm. A beam profiler also detected a sharper intensity edge, sharpening the FWHM edge width to 0.1mm. After optimizing details such as refining the axicon vertex angle to reduce intensity ripple along the propagation axis and smoothing the aspherical lens surface to eliminate mid-frequency interference, this solution was applied to a laser system for cutting float glass, operated by a 355nm picosecond solid-state laser. A high-quality ultraviolet (UV) Bessel beam with a cutting depth of 2.2mm was achieved, and the sharp intensity profile optimized the cross-section roughness. Detected by a 3D profilometer, the minimum surface roughness was reduced from 3.32μm to 1.94μm. This method shows promising prospects for efficient and high-quality optical glass cutting.