7 May 2018 Metasurface enhanced AFM cantilevers
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Abstract
In this contribution, we present the application of an optical metasurface polarization rotator in an Atomic Force Microscopy (AFM) setup. In AFM, the laser beam used to measure the cantilever deflection is not entirely intercepted by the cantilever surface. Consequently, the remainder of the beam illuminates part of the surface under measurement. Part of the light scattered by the surface is intercepted by the Position Sensitive Detector (PSD), interfering with the measurement of the light that is directly reflected by the cantilever. This reduces the measurement Signal-to-Noise Ratio (SNR), decreasing the AFM accuracy and generating artefacts. To enhance the SNR we propose a metasurface reflective polarization rotator, directly integrated on the cantilever. The metasurface elliptical resonators, oriented at a certain angle with respect to the incoming polarization state, will induce different phase shifts on the two components parallel to the orthogonal axes of the ellipse. By properly tuning the dimensions of the resonators, a 90° rotation of the reflected light polarization with respect to the incident polarization is realized. We arrive at three designs with cross-polar reflectivities of 0.82, 0.86 and 0.66 and total reflectivities of 0.83, 0.87 and 0.68 correspondingly. The metasurface allows to discriminate the desired light, reflected by the cantilever, from stray light from the sample surface, which maintains mostly the original polarization. In this paper, performance of the different configurations will be presented and discussed together with other considerations relative to the mechanical performances of the enhanced cantilever.
Conference Presentation
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B. Speet, B. Speet, F. Silvestri, F. Silvestri, G. Gerini, G. Gerini, S. Mashaghi Tabari, S. Mashaghi Tabari, H. Sadeghian, H. Sadeghian, } "Metasurface enhanced AFM cantilevers", Proc. SPIE 10671, Metamaterials XI, 1067122 (7 May 2018); doi: 10.1117/12.2307099; https://doi.org/10.1117/12.2307099
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