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Metacoatings for wavelength-scale, high-numerical-aperture plano–concave focusing lenses

2016; Optica Publishing Group; Volume: 33; Issue: 10 Linguagem: Inglês

10.1364/josab.33.002120

1520-8540

Mahin Naserpour, Carlos J. Zapata–Rodríguez, Carlos Díaz-Aviñó, Mahdieh Hashemi,

Plasmonic and Surface Plasmon Research

We design plano-concave silicon lenses with coupled gradient-index plasmonic metacoatings for ultrawide apertured focusing utilizing a reduced region of $\sim 20 \lambda^2$. The anomalous refraction induced in the planar input side of the lens and in the boundary of the wavelength-scale focal region boosts the curvature of the emerging wavefront, thus significantly enhancing the resolution of the tightly-focused optical wave. The formation of a light tongue with dimensions approaching those of the concave opening is here evidenced. This scheme is expected to have potential applications in optical trapping and detection.