Abstract-Multi-foci metalens for terahertz polarization detection

Ruoxing Wang, Jin Han, Jianlong Liu, Hao Tian, Weimin Sun, Li Li, and Xianzhong Chen

Schematic of the reflective THz multi-foci metalens for polarization detection. The ellipticity angle 𝜒$\chi$ and the direction of the major axis 𝛽$\beta$ of the incident and reflected polarization states are indicated in polarization ellipses.

https://www.osapublishing.org/ol/abstract.cfm?URI=ol-45-13-3506

We propose a reflective terahertz (THz) metalens with four focal points for polarization detection of THz beams. The metalens is composed of 𝑍$Z$-shaped resonators with spatially variant orientations, a reflective gold layer, and a dielectric spacer between them. The polarization states of the focal points include left circular polarization, right circular polarization, an incident polarization state, and a polarization state whose major axis is rotated 𝜋/4$\pi /4$ in comparison with that of the incident polarization. The handedness, ellipticity, and major axis of the polarization state can be determined based on the light intensities of the focal points. The uniqueness of the designed device renders this technique very attractive for applications in compact THz polarization detection and information processing.

Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Abstract-Graphene/liquid crystal hybrid tuning terahertz perfect absorber

Ruoxing Wang, Li Li, Tong Guo, Tianzhi Wang, Jianlong Liu, Hao Tian, Fengjun Tian, and Weimin Sun

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-58-34-9406

We present, by simulations, a metastructured graphene/liquid crystal hybrid tuning terahertz perfect absorber that consists of graphene disk resonator arrays above a metallic layer separated with liquid crystal substrate. The liquid crystal refractive index and the graphene Fermi level are utilized to implement double-tuning operation to push the spectra scanning limit of the terahertz absorber. Our simulations demonstrate high performance of a near-linear broad tuning region and near-unity absorbance with wide incident angle and polarization independence. The range of the resonant frequency scan is notably enlarged at a spectral ratio of as high as Δ𝑓/𝑓=50%$\mathrm{\Delta }f/f=50\mathrm{\%}$ while ensuring absorbance beyond 90%. Such graphene/liquid crystal hybrid tuning scheme would be preferable to push the working-band limit of terahertz perfect absorbers.

© 2019 Optical Society of America

Abstract-Triple-band tunable perfect terahertz metamaterial absorber with liquid crystal

Ruoxing Wang, Li Li, Jianlong Liu, Fei Yan, Fengjun Tian, Hao Tian, Jianzhong Zhang,  Weimin Sun,

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-26-32280

We report a compact triple-band tunable perfect terahertz metamaterial absorber (TMA) at the subwavelength scale of thickness, which is composed of a planar metallic disk resonator array above a conductive ground plane separated with liquid crystal (LC) mixture. The calculations of terahertz absorption spectra demonstrate triple near-unity absorption bands in the gap plasmonic resonance coupling regime. Three resonance frequencies of the absorber exhibit continuous linear-tunability as changing the refractive index of LC. Remarkably, each peak absorbance of the triple bands maintains at a level of beyond 99% in the whole tuning operation, and the absorbance can remain more than 90% over a wide range of incident angles. Our work suggests that the LC tunable absorber scheme has the potential to overcome the basic difficulty to perform simultaneously multiband spectral tuning and near-unity absorbance with wide angle of incidence and weak polarization dependence. The proposed LC-tunable multiband perfect TMA is promising in the application of biomolecular spectra-selective terahertz imaging and sensing.

© 2017 Optical Society of America under the terms of the OSA Open Access Publishing