A magnetically tunable non-Bragg defect mode in a corrugated waveguide filled with liquid crystals

Zhang, Lu; Fan, Ya-Xian; Liu, Huan; Han, Xu; Lu, Wenqiang

doi:10.1016/j.physleta.2018.02.017

Cited by 10 publications

(8 citation statements)

References 24 publications

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“…They can affect the amplitude as well as the phase of an optical field [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ]. One of their advantageous properties is tunability, which can be obtained by the application of external stimuli, such as electric [ 4 , 10 , 11 , 12 , 13 ], magnetic [ 14 , 15 , 16 , 17 ], and mechanical or optical fields [ 18 , 19 , 20 ].…”

Section: Introductionmentioning

confidence: 99%

Magnetically Tunable Liquid Crystal-Based Optical Diffraction Gratings

2020

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We present a theoretical analysis of optical diffractive properties of magnetically tunable optical transmission gratings composed of periodically assembled layers of a polymer and a ferromagnetic liquid crystal (LC). The orientational structure of the LC layers as a function of an applied magnetic field is calculated by minimization of the Landau-de Gennes free energy for ferromagnetic LCs, which is performed numerically and also analytically by using the one-constant approximation and the approximations of the high and the low magnetic fields. Optical diffractive properties of the associated diffraction structure are calculated numerically in the framework of rigorous coupled-wave analysis (RCWA). The presented methodology provides a basis for designing new types of diffractive optical element based on ferromagnetic LCs and simulating their operation governed by the in-plane magnetic field.

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Section: Introductionmentioning

confidence: 99%

Magnetically Tunable Liquid Crystal-Based Optical Diffraction Gratings

2020

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“…Passive modulation methods are referred to as “fixed” THz metamaterial patterns and are typically achieved by changing the geometrical parameters, for example, the periodicity, shape, dimension, and orientation, of the aperture of the THz bandpass metamaterials. Active tuning or modulation requires application of an external physical field (e.g., an electric field, magnetic field, mechanical deformation, optical pumping, or thermal stimulus) to the THz bandpass metamaterials, which will change the key resonance frequency parameters such as the location of THz resonance frequency, resonant transmission intensity, and FWHM bandwidth. In addition to these external physical fields, researchers have also developed a double‐layered tuning scheme to achieve effective THz modulation …”

Section: Modulation Methods Of Thz Transmission Resonancementioning

confidence: 99%

“…Existing research has proven that a magnetic field is also effective in terms of modulating the THz transmission properties . For the fabrication of a magnetically modulated THz bandpass filter, different types of waveguides (e.g., photonic crystal (PC) waveguides, substrate integrated waveguides (SIW), and semiconductor‐insulator‐semiconductor (SIS) waveguides) were built and tested. The effectiveness of achieving stable tunability for both center frequency and intensity of THz transmission for each of the waveguides has been demonstrated.…”

Section: Modulation Methods Of Thz Transmission Resonancementioning

confidence: 99%

“…The effectiveness of achieving stable tunability for both center frequency and intensity of THz transmission for each of the waveguides has been demonstrated. Some waveguides utilized magneto‐optical Bragg grating formed in SIS waveguides or non‐Bragg defect mode, and have been proven to effectively shift the resonance frequency with the presence of a magnetic field. For the underlying mechanism of THz modulation via a magnetic field, there is a limited number of explanations for the process mechanism.…”

Section: Modulation Methods Of Thz Transmission Resonancementioning

confidence: 99%

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Design, Fabrication, and Modulation of THz Bandpass Metamaterials

Wang

Gao

Raglione

et al. 2019

Laser & Photonics Reviews

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Development of terahertz (THz) sources, detectors, and optical components has been an active area of research across the globe. The interest in THz optoelectronics is driven by the various applications they have enabled, such as ultrawide‐band communication systems, air‐ and space‐borne astronomy, atmospheric monitoring, small‐scale radar, airport security scanners, ultrafast nanodevices, and biomedical imaging and sensing. Here, the aim is to provide a comprehensive review of THz bandpass metamaterials focusing on several areas. First, the design fundamentals and geometrical patterns of THz bandpass metamaterials are summarized. Second, fabrication methods of THz bandpass metamaterials are reviewed, including typical micro‐ and nanofabrication techniques and laser micromachining techniques. More importantly, different engineering methods are reviewed for tuning and modulation of the THz transmission resonance for these metamaterials. Both passive and active modulation methods are included in this discussion; the passive method involves changes in the geometrical pattern of the filter material, and the active method performs in situ modulation of properties by applying an external physical field. Finally, the potential applications and prospects for future research of THz bandpass metamaterials are discussed.

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“…Tunability is one of the important properties of diffraction gratings. Various tuning methods have been proposed; diffractive properties can be modulated by an applied electrical voltage [ 25 , 26 , 27 , 28 ], magnetic field [ 29 , 30 , 31 ], pressure, temperature, or by another electromagnetic wave [ 32 , 33 , 34 , 35 , 36 , 37 ]. Liquid crystals (LCs) are very suitable for the construction of tuneable optical diffraction gratings [ 38 , 39 ] since they possess a unique combination of mechanical softness and strong optical anisotropy that provides relatively easy control of LC molecules’ orientation.…”

Section: Introductionmentioning

confidence: 99%

Electrically Tuneable Optical Diffraction Gratings Based on a Polymer Scaffold Filled with a Nematic Liquid Crystal

et al. 2021

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We present an experimental and theoretical investigation of the optical diffractive properties of electrically tuneable optical transmission gratings assembled as stacks of periodic slices from a conventional nematic liquid crystal (E7) and a standard photoresist polymer (SU-8). The external electric field causes a twist-type reorientation of the LC molecules toward a perpendicular direction with respect to initial orientation. The associated field-induced modification of the director field is determined numerically and analytically by minimization of the Landau–de Gennes free energy. The optical diffraction properties of the associated periodically modulated structure are calculated numerically on the basis of rigorous coupled-wave analysis (RCWA). A comparison of experimental and theoretical results suggests that polymer slices provoke planar surface anchoring of the LC molecules with the inhomogeneous surface anchoring energy varying in the range 5–20 μJ/m2. The investigated structures provide a versatile approach to fabricating LC-polymer-based electrically tuneable diffractive optical elements (DOEs).

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A magnetically tunable non-Bragg defect mode in a corrugated waveguide filled with liquid crystals

Cited by 10 publications

References 24 publications

Magnetically Tunable Liquid Crystal-Based Optical Diffraction Gratings

Magnetically Tunable Liquid Crystal-Based Optical Diffraction Gratings

Design, Fabrication, and Modulation of THz Bandpass Metamaterials

Electrically Tuneable Optical Diffraction Gratings Based on a Polymer Scaffold Filled with a Nematic Liquid Crystal

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