Optical control of polarized terahertz waves using dye-doped nematic liquid crystals

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

doi:10.1063/1.5041294

Cited by 5 publications

(3 citation statements)

References 38 publications

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“…tunability [18], [21]. 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].…”

Section: Introductionmentioning

confidence: 92%

“…The measurements were conducted at 27°C, which is a LC phase temperature of 5CB. In the calculation, the thickness of the substrate was 2 mm, the refractive index of the substrate was 1.52 + i4×10 −4 , n o = 1.55 + i0.025, and n e = 1.69 + i0.01 [23], [41]. For simplicity, the frequency dispersions of these optical constants were ignored, and the other parameters are given above.…”

Section: Experimental Demonstrationmentioning

confidence: 99%

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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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Section: Introductionmentioning

confidence: 92%

Section: Experimental Demonstrationmentioning

confidence: 99%

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

et al. 2019

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“…LCs without metallic subwavelength structures can also realize fundamental active THz elements, such as phase, polarization, and intensity modulators [16] [22]. However, these LC THz elements have a problem in the response speeds [20], [21]. To obtain a sufficient phase shift or retardation for Manuscript received mm dd, yyyy; accepted mm dd, yyyy.…”

Section: Introductionmentioning

confidence: 99%

Highly Birefringent Terahertz Metasurfaces Based on a Liquid-Crystal-Embedded Metal Mesh

et al. 2022

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Here, we report a metasurface for polarization converters in the terahertz (THz) spectral range. The THz metasurface consists of a metal mesh with subwavelength isotropic apertures and a nematic liquid crystal (LC) that is a uniaxially anisotropic dielectric medium. The LC is embedded and aligned homogeneously in the apertures. We calculated the complex transmittance and complex reflectance of the LC-embedded metal mesh (LC metasurface) for the eigen-polarization states using the finite-difference time-domain method, and we then investigated the effective electromagnetic parameters. The LC metasurface exhibits birefringence of approximately 1, which is one order of magnitude larger than that of the LC, in the transmission band. We also investigated the relationship between the geometrical parameters of the LC metasurface and transmissive retardation. These results demonstrate that the LC metasurface is useful for transmissive polarization converters in the THz spectral range.

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Modulators for mid-infrared and terahertz light

Herrmann

Gao

Huang

et al. 2020

Journal of Applied Physics

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The rise of mid-infrared and terahertz wave technology over the past two decades has led to incredible insights and potential applications for next-generation optoelectronics. Modulators, which control amplitude, phase, and/or polarization of incident light, are widely used in communications, imaging, and sensing and are crucial for further development of technology functioning in the mid-infrared and terahertz frequency regimes. The lack of natural materials with optical responses in these frequency regimes has led to a surge in engineering efforts to create novel devices and architectures for achieving control over the properties of mid-infrared and terahertz radiation. Major efforts in the field have been devoted to studying carrier concentration modulation, liquid crystals, phase-change materials, and micro-electromechanical systems for controlling the light–matter interaction. Although there has been considerable progress in realizing mid-infrared and terahertz modulators, novel approaches are seeking higher modulation speed, more functionality, and miniaturized size. In this perspective, we review the recent advancements of modulators for mid-infrared and terahertz wavelengths. We discuss various modulation mechanisms, along with their relative performance, and consider future architectures to improve upon the current technology for mid-infrared and terahertz modulation.

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Optical control of polarized terahertz waves using dye-doped nematic liquid crystals

Cited by 5 publications

References 38 publications

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

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

Highly Birefringent Terahertz Metasurfaces Based on a Liquid-Crystal-Embedded Metal Mesh

Modulators for mid-infrared and terahertz light

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