关键词: 太赫兹/
人工超表面/
偏振转换/
偏振分束
English Abstract
Multifunctional metasurfaces for terahertz polarization controller
Yang Lei,Fan Fei,
Chen Meng,
Zhang Xuan-Zhou,
Chang Sheng-Jiang
1.Institute of Modern Optics, Nankai University, Tianjin 300071, China
Fund Project:Project supported by the National Basic Research Program of China (Grant No. 2014CB339800), the National Natural Science Foundation of China (Grant Nos. 61171027, 61505088), the Natural Science Foundation of Tianjin, China (Grant No. 15JCQNJC02100), and the National High Technology Research and Development Program of China (Grant No. 2011AA010205).Received Date:08 December 2015
Accepted Date:07 January 2016
Published Online:05 April 2016
Abstract:Polarization is one of the basic properties of electromagnetic wave conveying valuable information about signal transmission and sensitive measurements. Manipulations of polarization state and amplitude have aroused a lot of research interest in many different fields, especially in the terahertz (THz) regime. Although many researches on THz polarization controller have been carried out, their transmission losses are still difficult to lower in a broad bandwidth. And there are few reports on THz polarization controller which can rotate the polarization state and split beams at the same time. Multifunctional THz devices are required to meet the needs of the progress of THz technology and its applications. In order to overcome this constraint, semiconductor silicon is integrated into the proposed structure to manipulate the polarization state and the amplitude, because of its optical properties with the external pump light. Here, according to the electromagnetic resonance between split rings and silicon rings in Fabry-Prot-like cavity, we propose a metasurfaces-based terahertz polarization controller. The unite cell structure is composed of metal grids-split ring/Si ring-metal grids spaced by silica layers. By using the finite element method in CST Microwave Studio, we simulate the transport and polarization properties under different conditions. The results show that a linear polarization state can be nearly perfectly converted into its orthogonal one from 0.39 to 1.11 THz with a transmission loss of 1 dB, which fits well to the one of multiple-beam interference theory. Then we study the properties of the proposed metasurface structure for oblique incidence. The property of rotating polarization basically keeps stable even at an incident angle of 60 from 0.52 to 1.05 THz. At the end of the paper, the polarization splitting feature of the device is discussed in the THz regime. The results demonstrate that the transmitted and reflected beam power of the device can be tuned by changing the pump light power. The modulation depths of two beams reach more than 90% at 0.5 THz. It is worth noting that the proposed structure can not only rotate the polarization state of transmitted light in a broad bandwidth of 0.72 THz, but also modulate the transmitted and reflected beam power with a wide modulation depth. It can be used as a broad-band, low-loss and tunable terahertz polarization controller which is also insensitive to the incident angle. So it meets the requirements in THz communication, spectrum detection and imaging systems.
Keywords: terahertz/
metasurfaces/
polarization conversion/
polarization splitting
