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Temporal profile of THz pulse at various applied voltages after THz signal passes through (a) SLD and (b) MLD, and applied voltage-dependent phase shifts of (c) SLD and (d) MLD for various frequencies.
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This work develops a 2 pi Terahertz (THz) phase shifter that stacks three layers of cholesteric liquid crystal (CLC) cells. Each CLC cell in the focal conic state with randomly helical structures exhibits isotropic properties for a THz wave and enables polarization-independency. An external vertical electric field is applied to modulate the refract...
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We propose a reconfigurable terahertz (THz) metamaterial (RTM) to investigate its multifunctional electromagnetic characteristics by moving the meta-atoms of split-ring resonator (SRR) array. It shows the preferable and capable adjustability in the THz frequency range. The electromagnetic characteristics of the proposed RTM device are compared and...
Citations
... For example, an electrically tunable liquid LC shifter permeating NLCs into the resonant unit in the ka-band is proposed in [23]. In [24], a terahertz phase shifter with a phase-shifting range of 2π was proposed possessing a response time of less than 1s. Perez-Palomino et al. proposed an LC phase shifter unit composed of three parallel dipoles at 100 GHz [25]. ...
We propose an F-band phase shifter based on the nematic liquid crystals (NLCs). The proposed phase shifter is formed by a voltage-controlled cavity through introducing an NLC layer between a dipole structure array and a metal floor. Under the action of electric field, the orientation of the NLC molecules will be deflected. We adjust the resonant frequency and phase of the reflected electromagnetic (EM) wave by tuning the permittivity. The transmission characteristics and the LC parameters are calculated and analyzed for EM waves within the frequency range from 85 to 115 GHz. The LC-based device with a 30×30 array of two parallel unequal dipoles is printed on a quartz substrate, with 4 cm × 4 cm area and 490 μm thickness. The experimental results show that phase shift of zero to 350.7° is achieved at 104.2 GHz by changing the applied bias voltage on the LC layer from 0 to 20 V. Considering the anisotropy and inhomogeneity of the LC, an improved electrification model is established and compared with the test results. The proposed phase shifter is expected to find several applications in millimeter wave and terahertz reconfigurable antenna systems.
... In this report, using a 0.1-mm-thick LC layer, a voltage-controlled phase shift of ∼0.1 rad in the THz spectral range was demonstrated [17]. Wang et al. reported polarization-independent THz phase modulation using a chiral nematic LC [18,21]. They indicated that the domain structures in the randomly aligned nematic LC cause non-negligible scattering losses [18]. ...
... However, we can estimate that the switching-on time and the switching-off time are a few seconds and a few tens of seconds, respectively [20,43]. For practical use, the response times should be improved by using highly birefringent LCs, polymer-stabilized LCs, multi-layered structures, multi-electrode structures, highly birefringent metamaterials, etc [19,21,43,44]. ...
A polarization-independent terahertz (THz) phase shifter was proposed using a liquid crystal (LC) grating with subwavelength periodic alignment. The LC grating was constructed with one-dimensional periodic planar alignment and was designed based on the effective medium theory. The phase of the transmitted wave was theoretically independent of the polarization state and the phase was shifted by transition from a periodic planar alignment to a homeotropic alignment. The LC grating was fabricated using a nematic LC and photoalignment layers. The easy axes of the photoalignment layers were periodically regulated using a grating photomask with a subwavelength pitch. There was minimal dependence of the obtained phase shift on the polarization state, and the results were in agreement with the theoretical calculations.
... The optical solution promises better performances compared to its classical analogue that utilizes electrical or microelectromechanical system which are prone to signal distortion and unwanted electromagnetic interferences 1 . Various reconfigurable microwave functionalities have been demonstrated including cognitive radio applications 12 , microwave mixers 13 and phase shifters 14,15 . Although optically controlled microwave amplitude and phase switches have attracted appreciable attention due to their superior potential performances, they are not yet sufficiently advanced for implementation in practical microwave systems. ...
Microwave photonics uses light to carry and process microwave signals over a photonic link. However, light can instead be used as a stimulus to microwave devices that directly control microwave signals. Such optically controlled amplitude and phase-shift switches are investigated for use in reconfigurable microwave systems, but they suffer from large footprint, high optical power level required for switching, lack of scalability and complex integration requirements, restricting their implementation in practical microwave systems. Here, we report Monolithic Optically Reconfigurable Integrated Microwave Switches (MORIMSs) built on a CMOS compatible silicon photonic chip that addresses all of the stringent requirements. Our scalable micrometer-scale switches provide higher switching efficiency and require optical power orders of magnitude lower than the state-of-the-art. Also, it opens a new research direction on silicon photonic platforms integrating microwave circuitry. This work has important implications in reconfigurable microwave and millimeter wave devices for future communication networks.
... The idea of using light to control or even introduce signals directly into microwaves devices 7,13,14 has drawn great interest in the microwave community driven by the need for dynamic control, fast response, immunity to electromagnetic interference, and good isolation between the controlling and controlled devices. The optical solution promises better performances compared to its classical analogue that utilizes electrical or microelectromechanical system which are prone to signal distortion and unwanted electromagnetic interferences. 1 Various reconfigurable microwave functionalities have been demonstrated including cognitive radio applications 15 , microwave mixers 16 and phase shifters 17,18 . Although optically controlled microwave amplitude and phase switches have attracted appreciable attention due to their superior potential performances, they are not yet sufficiently advanced for implementation in practical microwave systems. ...
Microwave photonics uses light to carry and process microwave signals over a photonic link. However, light can instead be used as a stimulus to microwave devices that directly control microwave signals. Such optically controlled amplitude and phase-shift switches are investigated for use in reconfigurable microwave systems, but they suffer from large footprint, high optical power level required for switching, lack of scalability and complex integration requirements, restricting their implementation in practical microwave systems. Here, we report Monolithic Optically Reconfigurable Integrated Microwave Switches (MORIMSs) built on a CMOS compatible silicon photonic chip that addresses all of the stringent requirements. Our scalable micrometer-scale switches provide higher switching efficiency and require optical power orders of magnitude lower than the state-of-the-art. Also, it opens a new research direction on silicon photonic platforms integrating microwave circuitry. This work has important implications in reconfigurable microwave and millimeter wave devices for future communication networks.
We demonstrate indium-tin-oxide (ITO) finger-type pattern (FTP) as an effective transparent conducting electrode for terahertz (THz) application. The average transmittance of ITO-FTP is as high as 85% in the frequency range of 0.2–1.2 THz. A pair of fused silica substrates with ITO-FTP was employed for constructing an electrically tunable twisted nematic liquid crystal (LC) based THz phase shifter. The cross-orientation pair of ITO-FTPs served as wavelength-insensitive and transparent electrodes for the LC layer. A maximum phase shift exceeding π/2 at 1.2 THz was demonstrated for a device with a 600-μm-thick LC cell. The required driving voltage for quarter-wave operation and threshold voltage were 5.3 and 0.8
V
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, respectively. Performance of the THz phase shifter is discussed by defining a figure of merit (FOM) for LC-based THz shifters and compared with previously reported devices.
