Ultrafast Laser High-Aspect-Ratio Extreme Nanostructuring of Glass beyond <i>λ</i> /100

The ultimate feature size is key in ultrafast laser material processing. A capacity to substantially exceed optical limits and to structure below 100 nm is essential to advance ultrafast processing into the field of metamaterials. Such achievement requires combining the control of optical near-fields and of material reactions while preserving the flexibility of long working distances, compatible with a mature laser process. Using subpicosecond and picosecond nondiffractive Bessel beams, we demonstrate unprecedented feature sizes below a hundredth of the incident 1-μm wavelength over an extended focus depth of tens of micrometers. Record features sizes, down to 7 nm, result from self-generated near-field light components initiated by cavities induced by far-field radiation in a back-surface illumination geometry. This sustains the generation of more confined near-field evanescent components along the laser scan with a nanometer pitch, perpendicular to the incident field direction, driving a superresolved laser structuring process via local thermal ablation. The near-field pattern is replicated with high robustness, advancing toward a 10-nm nanoscribing tool with a micrometer-sized laser pen. The process is controllable by the field orientation. The nondiffractive irradiation develops evanescent fields over the focusing length, resulting in high-aspect-ratio trenching with a nanometer section and a micrometer depth. Higher energy doses trigger the self-organization of quasi-periodic patterns seeded by spatially modulated scattering, similarly to optical modelocking. A predictive multipulse simulation method validates the far-field-induced near-field electromagnetic scenario of void nanochannel growth and replication, indicating the processing range and resolution on the surface and in the depth.