Optically Tunable Terahertz Metasurfaces Using Liquid Crystal Cells Coated with Photoalignment Layers

An optically tunable terahertz filter was fabricated using a metasurface-imbedded liquid crystal (LC) cell with photoalignment layers in this work. The LC director in the cell is aligned by a pump beam and makes angles θ of 0, 30, 60 and 90° with respect to the gaps of the split-ring resonators (SRRs) of the metasurface under various polarized directions of the pump beam. Experimental results display that the resonance frequency of the metasurface in the cell increases with an increase in θ, and the cell has a frequency tuning region of 15 GHz. Simulated results reveal that the increase in the resonance frequency arises from the birefringence of the LC, and the LC has a birefringence of 0.13 in the terahertz region. The resonance frequency of the metasurface is shifted using the pump beam, so the metasurface-imbedded LC cell with the photoalignment layers is an optically tunable terahertz filter. The optically tunable terahertz filter is promising for applications in terahertz telecommunication, biosensing and terahertz imaging.

Multiple-band terahertz filter device using coupling effect of two nest metallic split-ring resonators

Multiple-band terahertz filter device consisting of two different-sized metallic split rings with the nested design method is proposed and investigated in this paper. Five separated filtering resonant dips having different resonance amplitudes and quality factors are gained, which are mainly attributed to the hybrid coupling effect between the two nested split-ring resonators. More importantly, the resonance features of the five filtering dips show a significant dependence on the designed parameters, especially the gap between two nested split rings. The multiple-band filtering resonance device given here can open up new avenues to control terahertz waves in many technology-related fields.