scholarly journals Liquid-Crystal-Based Phase Gratings and Beam Steerers for Terahertz Waves

2018 ◽  
Author(s):  
Ci-Ling Pan ◽  
Chia-Jen Lin ◽  
Chan-Shan Yang ◽  
Wei-Ta Wu ◽  
Ru-Pin Pan
Keyword(s):  
Liquid Crystal ◽  
Terahertz Waves

scholarly journals Optically Tunable and Thermally Erasable Terahertz Intensity Modulators Using Dye-Doped Liquid Crystal Cells with Metasurfaces

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1580
Author(s):  
Yi-Hong Shih ◽  
Harry Miyosi Silalahi ◽  
Ting-I Tsai ◽  
Yi-Chen Chen ◽  
Jou-Yu Su ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Pump Beam ◽  
Spatial Light Modulators ◽  
Terahertz Waves ◽  
Hot Plate ◽  
Light Modulators ◽  
Encryption And Decryption ◽  
Cell Scattering ◽  
Linearly Polarized ◽  
Crystal Cells

A terahertz metasurface that is imbedded into a dye-doped liquid crystal (DDLC) cell is fabricated in this work. After the metasurface-imbedded DDLC cell is irradiated with a linearly polarized pump beam, the irradiated cell is measured with a terahertz spectrometer. The irradiation of the pump beam causes the adsorption of the dye on one of the substrates of the cell, scattering incident terahertz waves and decreasing the transmittances of the terahertz metasurface at all the frequencies of its resonance spectrum. In addition, these transmittances decrease with an increase in the irradiation times of the pump beam. The adsorbed dye molecules are erased from the substrate after the cell is heated by a hot plate. The cell has similar spectra before the irradiation of the pump beam and after the heating of the hot plate. The aforementioned results reveal that the metasurface-imbedded DDLC cell is an optically tunable and thermally erasable terahertz intensity modulator. Therefore, this cell has the potential in developing intensity attenuators for terahertz imaging, frequency isolators for terahertz telecommunication, and spatial light modulators for terahertz information encryption and decryption.

scholarly journals Polymer stabilized liquid crystal phase shifter for terahertz waves

2013 ◽  
Vol 21 (10) ◽  
pp. 12395 ◽  
Author(s):  
Kristian Altmann ◽  
Marco Reuter ◽  
Katarzyna Garbat ◽  
Martin Koch ◽  
Roman Dabrowski ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Phase Shifter ◽  
Crystal Phase ◽  
Liquid Crystal Phase ◽  
Terahertz Waves ◽  
Polymer Stabilized

scholarly journals Effect of Thicknesses of Liquid Crystal Layers on Shift of Resonance Frequencies of Metamaterials

Coatings ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 578
Author(s):  
Wei-Fan Chiang ◽  
Shih-Xuan Lin ◽  
Yong-Xuan Lee ◽  
Yu-Han Shih ◽  
Jih-Hsin Liu ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Resonance Frequency ◽  
Long Range ◽  
Maximum Frequency ◽  
Terahertz Waves ◽  
Resonance Frequencies ◽  
Alignment Layers ◽  
Range Force ◽  
Terahertz Metamaterials ◽  
Frequency Shifting

A liquid crystal (LC) layer that is too thick exhibits a small terahertz birefringence due to the limited long-range force of the alignment layers that exert on it. An LC layer that is too thin has a small terahertz birefringence due to its invisibility to incident terahertz waves. Therefore, an LC layer may have a large terahertz birefringence at a specific thickness. It is well known that the birefringence of an LC layer dominates the shift of the resonance frequency of the metamaterial imbedded into the LC layer. As a result, this work studies the effect of the thicknesses of LC layers on the shift of the resonance frequencies of metamaterials. LC layers with various thicknesses ranging from 310 µm to 1487 µm are deposited on terahertz metamaterials, and each of the layers is aligned by two polyimide layers that are rubbed in a direction. The terahertz metamaterials have a maximum frequency shifting range of 21 GHz as 710 µm thick LC layers with mutually orthogonal rubbing directions are deposited on them. The maximum frequency shifting range arises from the competition between the long-range force of the polyimide layers and the interaction between the LC layers and their incident terahertz waves.

Temperature-dependent chirality of cholesteric liquid crystal for terahertz waves

2020 ◽  
Vol 45 (18) ◽  
pp. 4988
Author(s):  
Xin Zhang ◽  
Fei Fan ◽  
Yun-Yun Ji ◽  
Sheng-Jiang Chang
Keyword(s):  
Liquid Crystal ◽  
Cholesteric Liquid Crystal ◽  
Terahertz Waves ◽  
Temperature Dependent

Electrically Controlled Liquid Crystal Phase Grating for Terahertz Waves

2009 ◽  
Vol 21 (11) ◽  
pp. 730-732 ◽  
Author(s):  
Chia-Jen Lin ◽  
Chuan-Hsien Lin ◽  
Yu-Tai Li ◽  
Ru-Pin Pan ◽  
Ci-Ling Pan
Keyword(s):  
Liquid Crystal ◽  
Crystal Phase ◽  
Liquid Crystal Phase ◽  
Terahertz Waves ◽  
Phase Grating

Freeze-fracture TEM of the helical smectic A* phase

1992 ◽  
Vol 50 (1) ◽  
pp. 278-279
Author(s):  
K.J. Ihn ◽  
R. Pindak ◽  
J. A. N. Zasadzinski
Keyword(s):  
Liquid Crystal ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Freeze Fracture ◽  
Smectic Phase ◽  
Layer Spacing ◽  
Screw Dislocations ◽  
Smectic A ◽  
Smectic Phases ◽  
Discrete Amount

A new liquid crystal (called the smectic-A* phase) that combines cholesteric twist and smectic layering was a surprise as smectic phases preclude twist distortions. However, the twist grain boundary (TGB) model of Renn and Lubensky predicted a defect-mediated smectic phase that incorporates cholesteric twist by a lattice of screw dislocations. The TGB model for the liquid crystal analog of the Abrikosov phase of superconductors consists of regularly spaced grain boundaries of screw dislocations, parallel to each other within the grain boundary, but rotated by a fixed angle with respect to adjacent grain boundaries. The dislocations divide the layers into blocks which rotate by a discrete amount, Δθ, given by the ratio of the layer spacing, d, to the distance between grain boundaries, lb; Δθ ≈ d/lb (Fig. 1).

Attractive mode force microscopy of chiral liquid crystal surfaces

1992 ◽  
Vol 50 (1) ◽  
pp. 268-269
Author(s):  
B.D. Terris ◽  
R. J. Twieg ◽  
C. Nguyen ◽  
G. Sigaud ◽  
H. T. Nguyen
Keyword(s):  
Liquid Crystal ◽  
Crystal Surfaces ◽  
Free Surfaces ◽  
Control Range ◽  
Force Microscopy ◽  
Liquid Crystal Films ◽  
Chiral Liquid Crystal ◽  
Crystal Films ◽  
Electrostatic Charging ◽  
And Shifts

We have used a force microscope in the attractive, or noncontact, mode to image a variety of surfaces. In this mode, the microscope tip is oscillated near its resonant frequency and shifts in this frequency due to changes in the surface-tip force gradient are detected. We have used this technique in a variety of applications to polymers, including electrostatic charging, phase separation of ionomer surfaces, and crazing of glassy films.Most recently, we have applied the force microscope to imaging the free surfaces of chiral liquid crystal films. The compounds used (Table 1) have been chosen for their polymorphic variety of fluid mesophases, all of which exist within the temperature control range of our force microscope.

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