A simple method compatible with all geometrical structures of terahertz metamaterials for enhancing the tunability, sensitivity, Q-factor, and figure of merit (FOM) is proposed. This method uses a multi-layer SiO2:Ag to approach the floating-like double split ring resonators. The terahertz metamaterial consists of five layers of SiO2:Ag, in which each layer of SiO2:Ag comprises a 250-nm-thick SiO2 layer and a 50-nm-thick Ag layer. The tunability, sensitivity, Q-factor, and figure of merit (FOM) of metamaterial can be increased with increasing the number of layers of SiO2:Ag. Metamaterial with multi-layer SiO2-Ag has a larger tunability, sensitivity, Q-factor, and figure of merit (FOM) than the common metamaterial based on a single metal layer. The multi-layer metamaterial is an excellent achievement in developing biomolecule biosensors and can potentially sense dangerous viruses.
In this presentation, a rubbing-free LC device fabricated with organic Single-Crystal Rubrene (SCR) substrate has been investigated. The LC orientation on SCR is determined with capillary flowing direction of LCs, the SCR-coated LC cell has a homogeneous alignment with low pretilt angle. The SCR-based LC cell performs a wider thermal tolerance than that of the PI-based cell, owing to the strong anchoring property of SCR surface. SCR-based LC cell performs a lower operation voltage, faster response time, and higher voltage holding ratio than the PI-based LC cell. A rubbing-free modal LC device based on SCR layer is under development.
By controlling the deposition time of indium–tin–oxide (ITO) film, a high resistance of ultra-thin ITO (UTITO) layer can be realized. The UTITO layer is then deposited at the interface between the dielectric and LC layers in the hole-patterned liquid crystal (LC) lens. The UTITO application spreads the fringing field into the aperture hole center of LC lens and thus assists the LC reorientation therein. That considerably decreases the addressing voltage and switching-on time of LC lens. The UTITO LC lens also provides a wide tunable focus function, and preserves the lens quality and imaging performance as the conventional hole-patterned LC lens.
This study investigated a polyethylene terephthalate (PET) substrate and the effect of indium tin oxide (ITO) thin-film interference on the electromagnetic resonance of distorted metamaterials. The photoresist was developed on a PET substrate and swollen using isopropyl alcohol. The SRRs had various total lengths, gaps, and line widths. In addition, each of these three dimensions varied greatly and thus the distorted SRRs exhibited a broadband resonance spectrum. An ITO thin film was coated on the back of the PET substrate with a distorted metamaterials sample, and the terahertz spectrum was measured. The experimental results revealed that the ITO thin film can flatten the spectrum of the SRR sample. To determine the underlying reason, we varied the sheet resistance of the ITO film and observed the differences among the corresponding spectra. The flattened spectrum of the ITO films enhanced the thin-film interference effect of the PET substrate; consequently, the distorted metamaterials exhibited a flattened spectrum. These distorted metamaterials can be applied in terahertz imaging, terahertz communication systems, and optoelectronic integrated circuits.
Liquid crystal polymer (LCP) films are rolled into hollow cylinders. The hollow cylinders are measured by a terahertz spectrometer. Experimental results reveal that the transmittance spectra of the hollow cylinders have peaks at specific frequencies due to Fabry-Pérot resonance, and the frequencies of the peaks can be tuned by changing the thicknesses and rolled layers of the LCP films. Therefore, the rolled LCP films can be used to develop terahertz filters.
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