Dielectric metasurfaces are a class of flat‐optical elements that provide new ways to manipulate light. Irrespective of the underlying operation principle, the realization of such nanometer‐sized structures requires a high fabrication accuracy, e.g., to match resonant conditions. While electron‐beam lithography (EBL) achieves feature sizes below 10 nm, transparent substrates, as used for transmission devices, are challenging due to proximity effects. Furthermore, EBL's sequential exposure limits the exposable area, making it unaffordable for applications. Here, a novel fabrication route is described based on a master template created by EBL, which is then replicated by nanoimprint lithography (NIL). A three‐layer process enables high‐resolution nanoimprint resists with low etching selectivity with respect to semiconductors yet to be used. The resulting structures are highly reproducible and defect‐free thanks to the selective removal of residual layers and a master not suffering from proximity effects. Exemplarily, elliptical Mie resonators are fabricated with tunable resonances from the near infrared (NIR) to the visible wavelength regime. They reveal a high uniformity and sensitivity toward dielectric changes. The generic fabrication approach enables upscaling of nanoscale metasurfaces to wafer scales by step‐and‐repeat techniques and deployment of the optical devices fabricated in real‐world applications due to massively reduced costs.

Ablation of materials in combination with element-specific analysis of the matter released is a widely used method to accurately determine a material's chemical composition. Among other methods, repetitive ablation using femto-second pulsed laser systems provides excellent spatial resolution through its incremental removal of nanometer thick layers. The method can be combined with high-resolution mass spectrometry, for example, laser ablation ionization mass spectrometry, to simultaneously analyze chemically the material released. With increasing depth of the volume ablated, however, secondary effects start to play an important role and the ablation geometry deviates substantially from the desired cylindrical shape. Consequently, primarily conical but sometimes even more complex, rather than cylindrical, craters are created. Their dimensions need to be analyzed to enable a direct correlation with the element-specific analytical signals. Here, a post-ablation analysis method is presented that combines generic polydimethylsiloxane-based molding of craters with the volumetric reconstruction of the crater's inverse using X-ray computed tomography. Automated analysis yields the full, sub-micron accurate anatomy of the craters, thereby a scalable and generic method to better understand the fundamentals underlying ablation processes applicable to a wide range of materials. Furthermore, it may serve toward a more accurate determination of heterogeneous material's composition for a variety of applications without requiring time-and labor-intensive analyses of individual craters.

Laser ablation is nowadays an extensively applied technology to probe the chemical composition of solid materials. It allows for precise targeting of micrometer objects on and in samples, and enables chemical depth profiling with nanometer resolution. An in-depth understanding of the 3D geometry of the ablation craters is crucial for precise calibration of the depth scale in chemical depth profiles. Herein we present a comprehensive study on laser ablation processes using a Gaussian-shaped UV-femtosecond irradiation source and present how the combination of three different imaging methods (scanning electron microscopy, interferometric microscopy, and X-ray computed tomography) can provide accurate information on the crater’s shapes. Crater analysis by applying X-ray computed tomography is of considerable interest because it allows the imaging of an array of craters in one step with sub-µm accuracy and is not limited to the aspect ratio of the crater. X-ray computed tomography thereby complements the analysis of laser ablation craters. The study investigates the effect of laser pulse energy and laser burst count on a single crystal Ru(0001) sample. Single crystals ensure that there is no dependence on the grain orientations during the laser ablation process. An array of 156 craters of different dimensions ranging from <20 nm to ∼40 µm in depth were created. For each individually applied laser pulse, we measured the number of ions generated in the ablation plume with our laser ablation ionization mass spectrometer. We show to which extent the combination of these four techniques reveals valuable information on the ablation threshold, the ablation rate, and the limiting ablation depth. The latter is expected to be a consequence of decreasing irradiance upon increasing crater surface area. The ion signal generated was found to be proportional to the volume ablated up to the certain depth, which enables in-situ depth calibration during the measurement.