In the present work, we have investigated the combination of a superresolution microsphere-assisted 2D imaging technique with low-coherence phase-shifting interference microscopy. The imaging performance of this technique is studied by numerical simulation in terms of the magnification and the lateral resolution as a function of the geometrical and optical parameters. The results of simulations are compared with the experimental measurements of reference gratings using a Linnik interference configuration. Additional measurements are also shown on nanostructures. An improvement by a factor of 4.7 in the lateral resolution is demonstrated in air, thus giving a more isotropic nanometric resolution for full-field surface profilometry in the far field.
Nanoscale materials are nowadays widely used in many different modern technologies. Special attention is thus required for their characterization in order to optimize fabrication processes. However, current characterization systems which can achieve nanometric resolution over a large area and in three dimensions are few. Classical optical microscopy presents a resolving power limited by diffraction, making impossible the visualization of elements with a size under half the wavelength. Recently, several methods have thus been developed to overcome this limitation, among them microsphere-assisted microscopy. Indeed, using a transparent microsphere, a full-field image of the sample can be retrieved with a higher resolution than the diffraction-limit. In this paper, this new imaging technique is combined with phase-shifting interferometry in order to reconstruct the 3D surface of nanostructures. An enhancement of a factor of 4.0 in the lateral resolution is demonstrated while combining this with the nanometric axial sensitivity of interferometry. Results are shown of the topography of reference gratings as well as periodic Ag nano-dots on silicon and laser induced ripples in steel, spaced by a few hundred nanometres. A comparison of these results is made with those from SEM and atomic force microscopy. status solidi physica a Interference Microscopy www.pss-a.com
We demonstrate that photonic jets (PJs) can be obtained in the vicinity of a shaped optical fiber and that they can be used to achieve subwavelength etchings. Only 10% of the power of a 30 W, 100 ns, near-infrared (1064 nm) Nd:YAG laser, commonly used for industrial laser processing, has been required. Etchings on a silicon wafer with a lateral feature size close to half-laser wavelength have been achieved using a shaped-tip optical fiber. This breakthrough has been carried out in ambient air by using a multimode 100/140 μm silica fiber with a shaped tip that generates a concentrated beam at their vicinity, a phenomenon referred to as a PJ, obtained for the first time without using microspheres. PJ achieved with a fiber tip, easier to manipulate, opens far-reaching benefits for all PJ applications. The roles of parameters such as laser fluence, tip shape, and mode excitation are discussed. A good correlation has been observed between the computed PJ intensity distribution and the etched marks' sizes.
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