Abstract-Simultaneous excitation of extremely high-Q-factor trapped and octupolar modes in terahertz metamaterials

Shengyan Yang, Chengchun Tang, Zhe Liu, Bo Wang, Chun Wang, Junjie Li, Li Wang, Changzhi Gu,

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-14-15938&origin=search

Achieving high-Q-factor resonances allows dramatic enhancement of performance of many plasmonic devices. However, the excitation of high-Q-factor resonance, especially multiple high-Q-factor resonances, has been a big challenge in traditional metamaterials due to the ohmic and radiation losses. Here, we experimentally demonstrate simultaneous excitation of double extremely sharp resonances in a terahertz metamaterial composed of mirror-symmetric-broken double split ring resonators (MBDSRRs). In a regular mirror-arranged SRR array, only the low-Q-factor dipole resonance can be excited with the external electric field perpendicular to the SRR gap. Breaking the mirror-symmetry of the metamaterial leads to the occurrence of two distinct otherwise inaccessible ultrahigh-Q-factor modes, which consists of one trapped mode in addition to an octupolar mode. By tuning the asymmetry parameter, the Q factor of the trapped mode can be linearly modulated, while the Q factor of the octupolar mode can be tailored exponentially. For specific degree of asymmetry, our simulations revealed a significantly high Q factor (Q>100) for the octupolar mode, which is more than one order of magnitude larger than that of conventional metamaterials. The mirror-symmetry-broken metamaterial offers the advantage of enabling access to two distinct high-Q-factor resonances which could be exploited for ultrasensitive sensors, multiband filters, and slow light devices.

© 2017 Optical Society of America

Abstract-Single-layer plasmonic metasurface half-wave plates with wavelength-independent polarization conversion angle

Zhaocheng Liu, Zhancheng Li, Zhe Liu, Hua Cheng, Wenwei Liu, Chengchun Tang, Changzhi Gu, Junjie Li, Hou-Tong Chen, Shuqi Chen, and Jianguo Tian

ACS Photonics, Just Accepted Manuscript

DOI: 10.1021/acsphotonics.7b00491

Publication Date (Web): June 30, 2017

Copyright © 2017 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/acsphotonics.7b00491?journalCode=apchd5

Manipulation of polarization state is of great fundamental importance and plays a crucial role in modern photonic applications such as optical communication, imaging and sensing. Metamaterials and metasurfaces have attracted increasing interest in this area because they facilitate designer optical response through engineering the composite subwavelength structures. Here we propose a general methods of designing half-wave plate, and demonstrate in the near-infrared wavelength range an optically thin plasmonic metasurface half-wave plates that rotate the polarization direction of the linearly polarized incident light with a high degree of linear polarization. The half-wave plate functionality is realized through arranging the orientation of the nanoantennas to form an appropriate spatial distribution profile, which behave exactly as in classical half-wave plates but over in a wavelength-independent way.