Abstract
Broadband perfect metamaterial absorbers have been drawing significant attention in recent years. A close-to-unity absorption over a broad spectral range is established and this facilitates many photonic applications. A more challenging goal is to construct a broadband absorber with a tailored spectral absorption. The spectral absorption control and spectral shaping are very critical in many applications, such as thermal-photovoltaic, thermal emitters, spectrum imaging system, biomedical and extraterrestrial sensing, and refractive index sensor. In this work, one-dimensional (1D) planar stacking structure is designed to achieve the ultimate goal of a functionalized absorber with a fully tailorable spectral absorption. The lithography and etching process are totally eliminated in this proposed structure, and the fabrication is fully compatible with the regular silicon IC processing. By using ~2 nm ultra-thin metallic layers with a 10-pair (10X) SiO2/Si3N4 integrated dielectric filter, we can achieve decent spectral response shaping. The planar configuration of the ultra-thin-metal metamaterial perfect absorber (MPA) is the key to the easy design/integration of the dielectric filters on top of the MPA. Specifically, band-rejected, high-pass, low-pass and band-pass structure are constructed successfully. Finally, experimental evidence to support our simulation result is also provided, which proves the feasibility of our proposal.
Highlights
After the dielectric filter is implemented on top of the planar metamaterial perfect absorber (MPA), λ1 can still penetrate the filter and be absorbed by the MPA
The diffracted power after filter can be more difficult to be fully absorbed by the MPA since the MPA broadband absorption normally degrades with incidence angle
The physics behind the functional absorbers is seemingly quite simple: the filter shapes the spectral response by reflecting the photons with wavelengths in the rejection band
Summary
The advanced design for fully functional MPAs. Figure 2 shows the simulation structure. Absorption (BRJ) filter absorbs the photons in the reject band rather than reflects them. We show the experimental result of the band-reject (BRJ) structure In this case, Si3N4 and SiO2 is chosen to construct the filter part in our structure. Ti and SiO2 in the lower part of the structure act as a broadband MPA that shows excellent absorption in the VIS and NIR regimes Both reflectance (R) and transmittance (T) can be measured by ultraviolet visible near-infrared (UV-VIS-NIR) spectroscopy using Hitachi U-4100. This is the basis for that the measured response of our fabricated samples can be similar to the simulated ones
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