Infrared detection technology has important applications in laser ranging, imaging, night vision, and other fields. Furthermore, recent studies have proven that hot carriers which are generated by surface plasmon decay can be exploited for photodetection to get beyond semiconductors’ bandgap restriction. In this study, silicon nanopillars (NPs) and gold film at the top and bottom of silicon nanopillars were designed to generate surface plasmon resonance and Fabry–Perot resonance to achieve perfect absorption. The absorption was calculated using the Finite Difference Time Domain (FDTD) method, and factors’ effects on resonance wavelength and absorption were examined. Here we demonstrate how this perfect absorber can be used to achieve near-unity optical absorption using ultrathin plasmonic nanostructures with thicknesses of 15 nm, smaller than the hot electron diffusion length. Further study revealed that the resonance wavelength can be redshifted to the mid-infrared band (e.g., 3.75 μm) by increasing the value of the structure parameters. These results demonstrate a success in the study of polarization insensitivity, detection band adjustable, and efficient perfect absorption infrared photodetectors.
In this letter, a mechanical beam-scanning transmitarray antenna with a wide scan coverage is presented. A wide-band element is designed to provide a linear transmission phase shift with a low transmission loss, which comprises a double-arrow and two orthogonal grid polarizers printed on two substrates. Then, a dual-beam phase matching method is introduced to reduce the scan loss. To verify the design, a 437-element transmitarray with a circular aperture (D = 150 mm) is simulated, fabricated, and measured. The measured results indicate that the transmitarray antenna achieves a ±40°scan coverage while keeping a low scan loss (<1.8 dB). The side lobe levels keep lower than −15 dB in the entire scanning range. Moreover, a 1-dB gain bandwidth of 21% (14-17.2 GHz) can be achieved in terms of boresight radiation, and the measured peak gain is 23.5 dBi at 15 GHz.
In this paper, a novel low-profile, dual-polarized reflect-transmit-array antenna is proposed to independently control the forward and backward beams. A single-layer polarization-dependent element is designed with 0.1 λ0-thickness at 10 GHz, which comprises only two layers of metal patches printed on a dielectric substrate and two metallized vias. Through changing the polarization direction of the incident wave, the operating mode of the proposed array can be easily shifted among reflection mode, reflectiontransmission mode, as well as transmission mode. To verify the design concept, a circular reflect-transmitarray (D = 250 mm) is designed, fabricated, and measured. The measured results indicate a 1 dB bandwidth of 17% (9.8-11.5 GHz) in reflection mode and a measured peak gain of 24.2 dB at 10.5 GHz. Moreover, a 1 dB bandwidth of 6% (9.7-10.3 GHz) can be achieved in transmission mode, and the measured peak gain is 24.6 dB at 10 GHz. The results prove that the proposed design is promising for bidirectional wireless communication applications.
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