Reflective plasmonic waveplates based on metal–insulator–metal subwavelength rectangular annular arrays

• Reflective broadband plasmonic waveplate was proposed with MIM cavity structures.
• Electric fields can be well manipulated with both upper Au pattern and cavity length.
• The working wavelength bandwidth is much broadened with the cavity effect.
• Reflectivity is larger than 90% in a wide wavelength range of 130 nm.
• The circular polarization ellipticity of reflected light is >96% from 1.50 to 1.63 μm.

We propose and present a quarter-wave plate using metal–insulator–metal (MIM) structure with sub-wavelength rectangular annular arrays (RAA) patterned in the upper Au film. It is found that by manipulating asymmetric width of the annular gaps along two orthogonal directions, the reflected amplitude and phase of the two orthogonal components can be well controlled via the RAA metasurface tuned by the MIM cavity effect, in which the localized surface plasmon resonance dip can be flattened with the cavity length. A quarter-wave plate has been realized through an optimized design at 1.55 μm, in which the phase difference variation of less than 2% of the π/2 between the two orthogonal components can be obtained in an ultra-wide wavelength range of about 130 nm, and the reflectivity is up to ∼90% within the whole working wavelength band. It provides a great potential for applications in advanced nanophotonic devices and integrated photonic systems.

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