Abstract
Optical transmission through concentric circular nanoslits is studied in experiments and numerical simulations. Polarized optical microscopic imaging shows that the optical transmission through these apertures is spatially inhomogeneous, exhibiting colored fan texture patterns. Numerical simulations show that these colored fan texture patterns originate from the cylindrical vector polarization of the transmitted beam. Specifically, the transmitted light is in-phase radially polarized at long wavelengths due to the predominant transmission of the transverse magnetic (TM) waveguide modes; and in-phase azimuthally polarized at short wavelengths due to the increased optical transmission of the transverse electric (TE) waveguide modes. Additionally, the transmission shows a peak at the wavelength of Wood anomaly and a dip at the resonant wavelength of surface plasmon excitation; and the transmitted light at these wavelengths is a mixture of azimuthally and radially polarized fields. These interesting optical transmission behaviors of circular nanoslits provide a miniaturized way to generating radially and azimuthally polarized light.
Highlights
The discovery of extraordinary optical transmission through periodic arrays of subwavelength apertures in metal films has inspired considerable research interest owing to both its intriguing underlying physics and potential applications in a variety of fields such as quantum optics, optical wavelength filtering, nanolithography and sensing [1,2,3,4,5,6,7,8,9,10]
Optical transmission through concentric circular nanoslits is studied in experiments and numerical simulations
Polarized optical microscopic imaging shows that the optical transmission through these apertures is spatially inhomogeneous, exhibiting colored fan texture patterns
Summary
The discovery of extraordinary optical transmission through periodic arrays of subwavelength apertures in metal films has inspired considerable research interest owing to both its intriguing underlying physics and potential applications in a variety of fields such as quantum optics, optical wavelength filtering, nanolithography and sensing [1,2,3,4,5,6,7,8,9,10]. The dependence of the enhanced transmission on the grating periodicity is primarily attributed to the Wood anomalies and the excitation of surface plasmons at the metal surfaces [11,12,13,14,15,16], while the effects of aperture shapes are due to the Fabry-Perot type of cavity mode resonances inside individual subwavelength apertures [17,18,19,20,21]. We present experimental and numerical studies on optical transmission through individual apertures composed of concentric circular nanoslits in Ag films. The transmission exhibits a peak at the wavelength of Wood anomaly and a dip at the wavelength of the surface plasmon wave excitation; and the transmitted light at the Wood anomaly peak contains a mixture of azimuthally and radially polarized components and surface waves. The concentric circular nanoslits make it possible to generate azimuthally and radially polarized light in a very compact way
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