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Dual-band Frequency Selective Surface Bandpass Filters in Terahertz Band
Limei Qi,Chao Li 한국광학회 2015 Current Optics and Photonics Vol.19 No.6
Terahertz dual-band frequency selective surface filters made by perforating two different rectangularholes in molybdenum have been designed, fabricated and measured. Physical mechanisms of the dual-bandresonant responses are clarified by three differently configured filters and the electric field distributiondiagrams. The design process is straightforward and simple according to the physical concept and someformulas. Due to the weak coupling between the two neighboring rectangle holes with different sizes inthe unit cell, good dual-band frequency selectivity performance can be easily achieved both in the lowerand higher bands by tuning dimensions of the two rectangular holes. Three samples are fabricated, andtheir dual-band characteristics have been demonstrated by a THz time-domain spectroscopy system. Different from most commonly used metal-dielectric structure or metal-dielectric-metal sandwiched filters,the designed dual-band filters have advantages of easy fabrication and low cost, the encouraging resultsafforded by these filters could find their applications in dual-band sensors, THz communication systemsand other emerging THz technologies
Limei Qi 한국광학회 2016 Current Optics and Photonics Vol.20 No.2
Broadband metal-dielectric-metal terahertz filters composed of complementary rings are designed anddemonstrated. Four samples with different parameters were fabricated. Results measured using THztime-domain spectroscopy system show excellent agreement with simulations. Compared with thebroadband filters reported before, the complementary ring structure in our design is insensitive to anypolarization at normal incidence due to symmetry of the ring. Furthermore, the influence of structureparameters (such as period, radius, slot width, thickness and incidence angles) on the transmissioncharacteristics has been investigated theoretically. The encouraging results afforded by designing of thefilters could find applications in broadband sensors, terahertz communication systems, and other emergingterahertz technologies.
Broad Dual-band Metamaterial Filter with Sharp Out-of-band Rejections
Qi, Limei,Shah, Syed Mohsin Ali Optical Society of Korea 2018 Current Optics and Photonics Vol.2 No.6
A broad dual-band terahertz metamaterial filter with sharp out-of-band rejections is designed and demonstrated. The center frequencies of the first and the second bands occur at 0.35 THz and 0.96 THz with 3 dB relative bandwidth of 31% and 17%, respectively. Results are measured using a THz time-domain spectroscopy system that shows agreement with simulations. Physical mechanisms of the broad dual-band resonance are clarified based on transmissions of different structures and surface current density distributions. Influence of structure parameters on the transmission characteristics are discussed. Symmetry of the structure ensures the filter polarization independence at normal incidence. These results supported by the design of the filter could find applications in broad multi-band sensors, terahertz communication systems, and other emerging terahertz technologies.
Xu Zhang,Zeyong Wei,Yuancheng Fan,Limei Qi 한국물리학회 2017 Current Applied Physics Vol.17 No.6
A reflective metamaterial polarization transformer (RMPT) is proposed with closed fish-scale structure for high efficient cross-polarization reflection. The maximum efficiency of cross-polarization reflection for normal incidence is 97.2%. The RMPT maintains good performance for incident angles up to 25, and the RMPT is not restricted to a specific polarization state of the incident wave. Furthermore, the designed RMPT shows excellent structural tunability by optimizing the structural parameters, which makes it userfriendly.