- 标题
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- 实验方案
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Active broadband manipulation of terahertz photonic spin based on gyrotropic Pancharatnam-Berry metasurface
摘要： Controlling terahertz (THz) waves, especially the polarization state and deflection angle, is important in THz application systems. But most of conventional THz metasurfaces have limitations in efficiency and working bandwidth. Although Pancharatnam-Berry excellent manipulation for the circular polarized (CP) waves (or called photonic spin states) without phase dispersion, there is still challenge in active controlling. Here, we developed a magnetically tunable gyrotropic P-B metasurface by combining the gyroelectric semiconductor InSb and the P-B elements, which obtain two important effects: One is the active photonic spin Hall effect, which controls the conversion between two CP states and the deflection in space. A broadband working frequency of 1.02~1.7 THz is obtained with the sweeping deflection angle from 36.6° to 83.5° and the highest efficiency of over 70%. The other is photonic spin filter effect, which reflects one CP state but absorb the other orthogonal CP state, realizing nonreciprocal absorption with the isolation of 24 dB. This active, high efficiency and broadband P-B metasurface opens a new way in manipulation of the THz wave propagation and polarization states in both space and frequency domains.
关键词： Magneto-optical device,terahertz,subwavelength structure
更新于2025-09-23 15:21:01
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Mathematical Analysis of Surface Plasmon Resonance by a Nano-Gap in the Plasmonic Metal
摘要： We develop a mathematical theory for the excitation of surface plasmon resonance on an infinitely thick metallic slab with a nano-gap defect. Using layer potential techniques, we establish the well-posedness of the underlying scattering problem. We further obtain the asymptotic expansion of the scattering solution in order to characterize the leading-order term of the surface plasmonic waves, and derive sharp estimates for both the plasmonic and nonplasmonic parts of the solution. The explicit dependence of the surface plasmon resonance on the size of the nano-gap, and the real and imaginary parts of the metal dielectric constant, are given.
关键词： surface plasmon resonance,Helmholtz equation,subwavelength structure,integral equation
更新于2025-09-16 10:30:52
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Flexible Linear and Angular Displacement Sensor Based on a Gradient Guided-Mode Resonance Filter
摘要： This paper reports a method for micrometer-scale linear and angular displacement measurement based on a gradient grating period guided-mode resonance (GGP-GMR) filter. When the filter is mounted on a moving or rotating object, the displacement on the object can be observed through the changes in the resonant wavelength, which are detected by the GGP-GMR filter. In this paper, the GGP-GMR filter comprised grating periods from 250 to 550 nm with 2-nm increments. Each period comprised 100 repeated cycles, resulting in a total length of 6 mm. For linear displacement, we achieved an average sensitivity of 67 nm/mm for a detection range of 6 mm and a theoretical limit of detection of 3 μm. To demonstrate the measurement of angular displacement, the GGP-GMR filter was attached to a cylinder with a diameter of 8 cm. The experimental results revealed an average sensitivity of 51.7 nm/° for a range of 7° and an experimental limit of detection of 0.002°.
关键词： sensor,guided-mode resonance,subwavelength structure,bandstop filter,Displacement measurement
更新于2025-09-10 09:29:36
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Preparation and protection of ZnS surface sub-wavelength structure for infrared window
摘要： Zinc sulfide (ZnS) is one of the most important far-infrared optical candidate materials. However, it is indispensable for ZnS to improve its antireflection and protection especially under harsh environments. Compared with conventional surface antireflective films, surface sub-wavelength structures (SWSs) have some unique advantages. In this paper, dewetting nickel dots as etching mask on ZnS substrates were obtained by thermal annealing of as-sputtered Ni films on the intermediate layers of as-sputtered silicon films. ZnS SWSs were then prepared by inductively coupled plasma (ICP) etching. Finally, HfO2 films were deposited on ZnS SWSs by atomic layer deposition. The influences of SWSs and ALD-derived HfO2 films on the transmittance and protection of ZnS were both investigated. The experimental results show that ZnS SWSs can increase both far-infrared transmittance and surface hydrophobicity. Meanwhile, ALD-derived HfO2 films can provide good protection. Compared with bare ZnS, HfO2-coated ZnS with double-sided SWS exhibits average transmittance of 79.2% other than initial 69.1% in 8–12 μm, better hydrophobicity with the wetting angle of 119.7°, and higher composite nano-hardness increased from 25.00 to 38.68 GPa. ALD derived HfO2 films on ZnS surface sub-wavelength structures have excellent application prospective for infrared optical windows.
关键词： Subwavelength structure,Antireflection,Infrared window,ZnS,Protection
更新于2025-09-09 09:28:46