Twisted nematic liquid crystal cells with rubbed poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) films for active polarization control of terahertz waves

Sasaki, Tomoyuki; Okuyama, H.; Sakamoto, Moritsugu; Noda, Kohei; Okamoto, Hiroyuki; Kawatsuki, Nobuhiro; Ono, Hiroshi

doi:10.1063/1.4981244

Cited by 24 publications

(14 citation statements)

References 37 publications

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“…which are then fed back into (11) for the final update equation of the electric field E. Note that in 3D problems, a special treatment is required at the interfaces between DS and dielectric materials on the x-y plane, whose update equations are also obtained from the integral form of Maxwell's equations by proper volume averaging the values of media parameters. The algorithm's validity is demonstrated by calculating the transmittance T (f ) of a 100-nm film of PEDOT:PSS, whose DS parameters are given in Table 1 [7]. The substrate is a 545-µm slice of lossless silica (ε s = 3.842).…”

Section: Theoretical and Experimental Studies Of Terahertz Thin Cmentioning

confidence: 99%

“…Compared to bulky conducting materials, such as metals, whose EM response follows the Drude model (electron gas), carriers in TCF can be localized and trapped leading to back-scattering events. This behavior can be captured by an extended Drude-Smith (DS) model [5], which has provided excellent fits for numerous TFC, among which Ag nanowires [6], PEDOT:PSS [4], [7], ZnO films and nanowires [8], [9], ITO nanowhiskers [10], phase transitions in vanadium oxide films [11], and silicon nanocrystals [12].…”

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confidence: 99%

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Numerical and Experimental Time-Domain Characterization of Terahertz Conducting Polymers

Zografopoulos

Prokopidis

Ferraro

et al. 2018

IEEE Photon. Technol. Lett.

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A comprehensive framework for the theoretical and experimental investigation of thin conducting films for terahertz applications is presented. The electromagnetic properties of conducting polymers spin-coated on low-loss dielectric substrates are characterized by means of terahertz time-domain spectroscopy and interpreted through the Drude-Smith model. The analysis is complemented by an advanced finite-difference time-domain algorithm, which rigorously deals both with the dispersive nature of the involved materials and the extremely subwavelength thickness of the conducting films. Significant agreement is observed among experimental measurements, numerical simulations, and theoretical results. The proposed approach provides a complete toolbox for the engineering of terahertz optoelectronic devices.

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Section: Theoretical and Experimental Studies Of Terahertz Thin Cmentioning

confidence: 99%

mentioning

confidence: 99%

Numerical and Experimental Time-Domain Characterization of Terahertz Conducting Polymers

Zografopoulos

Prokopidis

Ferraro

et al. 2018

IEEE Photon. Technol. Lett.

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“…We also reported a THz polarization converter with photothermal control, using a dye-doped LC [23]. However, common LC THz devices have problems with response speed [22], [25]. To obtain sufficient phase shifts or polarization changes for THz waves, the thickness of the LC layer should be comparable to the submillimeter to millimeter wavelength [22].…”

Section: Introductionmentioning

confidence: 99%

“…However, common LC THz devices have problems with response speed [22], [25]. To obtain sufficient phase shifts or polarization changes for THz waves, the thickness of the LC layer should be comparable to the submillimeter to millimeter wavelength [22]. For example, in homogeneously aligned nematic LCs, the time for the Freedericksz transition for a vertically applied voltage is proportional to the square of the LC layer thickness [26].…”

Section: Introductionmentioning

confidence: 99%

Active Terahertz Polarization Converter Using a Liquid Crystal-Embedded Metal Mesh

et al. 2019

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We report a terahertz (THz) metamaterial consisting of a metal mesh layer with nematic liquid crystals (LCs). The metal mesh has subwavelength apertures that function as a bandpass filter in the THz spectral range. The LCs are embedded and aligned homogeneously in the apertures. The electromagnetic characteristics were calculated with a finite-difference time-domain method. The metamaterial converts the polarization of the THz wave during transmission and the thickness of the LC layer can be reduced by two orders of magnitude relative to the homogeneously aligned LC without the meta-structures. This increases the response speed to applied external fields. We also fabricated the metamaterial using a dielectric substrate with a metal mesh layer, a nematic LC, and a dielectric substrate with a polymeric alignment layer and investigated its polarization conversion using THz time-domain spectroscopy. The experimental results demonstrated that metal mesh structures with LCs are useful for active THz polarization converters.

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“…This can be attributed to the fact that the transmittance of a homogenously aligned LC cell exhibits more explicit dependence on the wavelength [18]. In related work, Sasaki et al [19] fabricated a THz polarization converter using a twisted nematic (TN) LC cell structure with pristine PEDOT/PSS films as TCE. A 1 mm thick TN cell was used and a driving voltage of approximately 15 V was applied to decrease the transmittance of the device to zero.…”

Section: Introductionmentioning

confidence: 99%

Twisted Nematic Liquid-Crystal-Based Terahertz Phase Shifter using Pristine PEDOT: PSS Transparent Conducting Electrodes

et al. 2019

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For this study, we demonstrated three different types of twisted nematic (TN) liquid crystal (LC) terahertz (THz) phase shifters using pristine poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT: PSS) thin films as transparent conducting electrodes (TCEs). The transmittance of spin-coated pristine PEDOT: PSS thin film was as high as 92% in the frequency range of 0.2–1.2 THz. This is among the highest reported. Several TN-LC cells were constructed in a comparative study, which confirmed the reliability of pristine PEDOT: PSS as a TCE layer for THz phase shifter applications. The highest phase shift, required root-mean-square (RMS) driving voltage, and threshold voltage achieved by devices tested were 95.2° at 1 THz, 7.2 VRMS, and 0.5 VRMS, respectively. The thickness of the LC layer for the phase shifter was 250 µm, approximately half as thick as previous designs. In addition, the pristine PEDOT: PSS-based TN-LC phase shifter exhibited a figure-of-merit (FOM) value of approximately 6.65 degree·dB−1·V−1. This compared favorably with previously reported homogeneously aligned phase shifters with an FOM of 2.19 degree·dB−1·V−1. Our results indicated that a twisted nematic LC cell with pristine PEDOT: PSS thin films as electrodes is a good combination for a THz phase shifter and wave plates as well as other LC-based THz devices.

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Twisted nematic liquid crystal cells with rubbed poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) films for active polarization control of terahertz waves

Cited by 24 publications

References 37 publications

Numerical and Experimental Time-Domain Characterization of Terahertz Conducting Polymers

Numerical and Experimental Time-Domain Characterization of Terahertz Conducting Polymers

Active Terahertz Polarization Converter Using a Liquid Crystal-Embedded Metal Mesh

Twisted Nematic Liquid-Crystal-Based Terahertz Phase Shifter using Pristine PEDOT: PSS Transparent Conducting Electrodes

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