Abstract
Over the years, there has been increasing interest in the integration of metal hole array (MHA) with optoelectronic devices, as a result of enhanced coupling of incident light into the active layer of devices via surface plasmon polariton (SPP) resonances. However, not all incident light contributes to the SPP resonances due to significant reflection loss at the interface between incident medium and MHA. Conventional thin-film antireflection (AR) coating typically does not work well due to non-existing material satisfying the AR condition with strong dispersion of MHA’s effective impedances. We demonstrate a single-layer metasurface AR coating that completely eliminates the refection and significantly increases the transmission at the SPP resonances. Operating at off-resonance wavelengths, the metasurface exhibits extremely low loss and does not show resonant coupling with the MHA layer. The SPP resonance wavelengths of MHA layer are unaffected whereas the surface wave is significantly increased, thereby paving the way for improved performance of optoelectronic devices. With an improved retrieval method, the metasurface is proved to exhibit a high effective permittivity () and extremely low loss (tan δ ~ 0.005). A classical thin-film AR coating mechanism is identified through analytical derivations and numerical simulations.
Highlights
To completely eliminate the reflection, the dielectric coating has to satisfy the AR condition, zc = zs and tc = λ/4, where tc is the thickness of the coating layer, λ is the wavelength in the coating material, zc = μc/ c and zs = μs/ s are the impedances, c and s are permittivities, and μc and μs are permeabilities of the coating material and substrate, respectively
Our metamaterial based antireflection (Meta-AR) coating consists of a planar metallic disk array (MDA) on the top of a cured layer of benzencyclobutene (BCB)
For comparison of MM operating as the AR (Meta-AR) coating with conventional AR coating, we designed three types of samples, namely the uncoated metallic hole array (MHA), a BCB layer coated MHA and MHA coated with an array of circular Au disks (MDA) atop the BCB layer
Summary
Simulated transmission for MHA with Meta-AR coating at (b) the first-order and (c) second-order SPP resonance wavelengths when dMDA is varied from 0.9 μm (0.5 · p) to 1.44 μm (0.8 · p) with a step of 0.09 μm (0.05 · p) and tBCB is changed in the same manner as (a). The meta-AR coating can be understood intuitively as the classical thin-film AR coating that consists of two thin flims, i.e. MDA metafilm and BCB layer Both the effective surface susceptibilities, χse and χsm in the metasurface model[24,25] and εeff and μeff in the retrieval method[26] are calculated using the transmission and reflection coefficients of an air-MM-air configuratoin.
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