Abstract-Passively Tunable Terahertz Filters Using Liquid Crystal Cells Coated with Metamaterials

 

 Wei-Fan Chiang ,Yu-Yun Lu ,Yin-Pei Chen ,Xin-Yu Lin ,Tsong-Shin Lim ,Jih-Hsin Liu ,Chia-Rong Lee , Chia-Yi Huang

https://www.mdpi.com/2079-6412/11/4/381

Liquid crystal (LC) cells that are coated with metamaterials are fabricated in this work. The LC directors in the cells are aligned by rubbed polyimide layers, and make angles θ of 0°, 45°, and 90° with respect to the gaps of the split-ring resonators (SRRs) of the metamaterials. Experimental results display that the resonance frequencies of the metamaterials in these cells increase with an increase in θ, and the cells have a maximum frequency shifting region of 18 GHz. Simulated results reveal that the increase in the resonance frequencies arises from the birefringence of the LC, and the LC has a birefringence of 0.15 in the terahertz region. The resonance frequencies of the metamaterials are shifted by the rubbing directions of the polyimide layers, so the LC cells coated with the metamaterials are passively tunable terahertz filters. The passively tunable terahertz filters exhibit promising applications on terahertz communication, terahertz sensing, and terahertz imaging. 

Abstract-Effect of swelling of a photoresist on electromagnetic resonance of terahertz metamaterials

Wei-Fan Chiang, Yu-Ting Hsieh, Song-Hang Wang, Hsin-Yuan Miao, Jih-Hsin Liu, and Chia-Yi Huang

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-41-12-2879

This work uses isopropyl alcohol (IPA) to develop a photoresist. IPA dissolves the photoresist that is not exposed to UV light, and swells the photoresist that is exposed to UV light. The swelling of the photoresist distorts the split-ring resonators (SRRs). The distorted SRRs have a larger loop length, smaller line width, and smaller split gap than undistorted SRRs. The change in the dimensions of the SRRs is caused by the extension of the SRR arms in their longitudinal directions. The resonance frequency of the distorted SRRs is smaller than that of the undistorted SRRs, and the resonance frequency decreases with the development time. The resonance frequency of the distorted SRRs depends on not only their dimensions, but also the bending of their arms. The distorted SRRs in this work have a frequency tuning range with a maximum width of 0.13 THz. The method that is proposed herein uses IPA to fabricate passively tunable terahertz metamaterials, which exhibit the advantages of high reliability, low cost, and ease of fabrication.

© 2016 Optical Society of America

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