We characterize engineered nanostructures with sizes smaller than half a wavelength using spectrally resolved interferometry. We analyze the response of the meta-atom of interest, which has a raspberry-like geometry. To identify the origin of the response, the study of individual building blocks, namely individual gold and silica nano-spheres, are first examined in this paper. Due to the fact that the size of the object is smaller than the resolution limit, phase information plays an important role in our analysis.
In this work we study the evolution of the photonic nanojet (PNJ) phenomenon as the ratio of the sphere’s diameter over the illumination wavelength changes, for microspheres with diameters from 2μm to 100μm. We measure the focal point position by using 3D intensity scanning and identifying the maximum-intensity spot. We also measure the spot size at the focal plane using both intensity and phase data. Finally we use this information to compare the PNJ’s behavior to that of a ball lens and evaluate the importance of chromatic effect in the PNJ phenomenon.
In this work we demonstrate the advantages of investigating diffractive optical elements in the phase domain. In this regime we can detect features that are not restrained by the diffraction limit and relate them to the geometrical and optical properties of the sample under test. To accomplish that, we use the custom made spectral high resolution interference microscope. Phase map recordings allow for easier and more precise localization of the positions, where phase changes happen. We show the localization capabilities by detecting phase singularities created by a trench. We also apply the concept to abrupt phase jumps of a phase diffractive component and determine the achievable resolution.
During the fabrication process of microlenses, characterization is essential for two purposes: evaluate the optical quality of the element and provide surface information feedback for process optimization. However, no technique can fulfill these two objectives at the same time. Interferometry is used for quality evaluation and optical profilometry for process optimization. In order to address this problem, we propose to use a high resolution interference microscope to characterize microlenses. The focusing capacity can be directly measured by recording the field near the focal spot at different wavelengths. Information about the microlens surface can also be retrieved. All this is illustrated for the front focus of a fused-silica microlens.