论文和技术资料

Ultrashort-pulse laser processing has become a key enabling technology for the precise, contactless modification of transparent materials, with applications ranging from waveguide writing to micro-drilling, dicing, and cleaving. The interaction of these pulses with transparent materials relies on a series of nonlinear absorption mechanisms, including multiphoton and avalanche ionization, triggered by the high peak intensities achievable with ultrashort pulses. These mechanisms generate a localized free-electron plasma whose density, geometry, and energy relaxation pathways ultimately determine the resulting structural modification, whether it be refractive index change, void formation, or ablation. At fluences close to the ablation threshold, when the focal volume coincides with the sample surface, the resulting modifications typically take the form of shallow craters. Their lateral dimensions are constrained near the diffraction limit of the focusing optics, while their depths are limited to a few hundred nanometers, since the electron plasma responsible for material removal remains confined near the surface. This limits the aspect ratio achievable with conventional temporal Gaussian beams and constrains their usefulness for applications requiring high-aspect-ratio features, such as through-glass vias or controlled crack propagation for dicing. Temporal pulse shaping offers a route to overcoming this limitation by reshaping the spatiotemporal distribution of the induced plasma. In particular, pulses imprinted with a temporal Airy profile characterized by an asymmetric, self-accelerating intensity envelope redistribute the deposited energy along the propagation direction rather than confining it to the surface. This altered energy deposition modifies the electron plasma distribution, promoting the formation of ultranarrow craters that extend several microns into the material, representing a marked increase in aspect ratio compared to their temporal Gaussian-pulse counterparts. In this work, we investigate this effect experimentally in fused silica, a benchmark high-bandgap dielectric, using pulses with tailored temporal Airy profiles generated by our temporal pulse shaper. We characterize the resulting surface modifications using focus ion beam cuts and scanning electron microscopy. To interpret the observed morphologies, we complement the experimental results with numerical simulations performed in COMSOL Multiphysics, using the heat transfer module to model the thermal response of the material following plasma-mediated energy deposition. The simulations reproduce the elongated, narrow crater morphology observed experimentally, showing good quantitative agreement in both lateral extent and depth, and support the proposed mechanism of subsurface-shifted plasma formation as the origin of the enhanced aspect ratio. These results establish temporal Airy pulses as an effective strategy for controlling the depth and aspect ratio of laser-induced surface modifications in transparent dielectrics. Because the underlying mechanism depends primarily on nonlinear ionization dynamics common to wide-bandgap materials, this approach is expected to be extendable beyond fused silica to other high-bandgap materials such as sapphire or borosilicate glass, opening potential applications in precision dicing, cleaving, and via formation for microelectronics and photonics manufacturing.