Scanning White Light Interferometry is a non-contacting method for three-dimensional (3D) surface characterization that provides Angstrom level vertical resolution and diffraction limited lateral resolution. This lateral resolution can be improved by implementing a photonic nanojet (PNJ) generating structure. The new method - Photonic Nanojet Interferometry (PNI) allows nanometer vertical resolution and lateral resolution better than 100 nm. In this work, a new design of a PNI system is proposed. The PNJ generating structure is a high refractive index microsphere embedded in a polymer material. We model the entire PNI objective in commercial software (Rsoft FullWAVE) and choose optimal parameters for the construct in such a way, that the working distance (FoV) is maximized while the width of the PNJ is kept below the diffraction limit. To test the new system, we imaged the data layer of a recordable Blu-ray Disc (BD). The results show that the proposed interferometer has two times higher magnification and two times larger field of view compared to the previous design featuring a 11 μm melamine formaldehyde micro-sphere. The new design also increases the fringe contrast by 1.5 times and provides easier handling of big samples by allowing them to be scanned.

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I. Kassamakov, G. Maconi, M. Järvinen, A. Nolvi, T. Vainikka, P. Raatikainen, T. Arstila, T. Ylitalo, I. Ninca, K. Ahlers, and E. Hæggström, "Label-free 3D super-resolution nanoscope," Proc. SPIE 11056, Optical Measurement Systems for Industrial Inspection XI, 110560S (Presented at SPIE Optical Metrology: June 25, 2019; Published: 21 June 2019); https://doi.org/10.1117/12.2526111.