scholarly journals Coupling of Defect Modes in Cholesteric Liquid Crystals Separated by Isotropic Polymeric Layers

Polymers ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 805 ◽  
Author(s):  
Shaohua Gao ◽  
Yanzi Zhai ◽  
Xinzheng Zhang ◽  
Xiao Song ◽  
Jiayi Wang ◽  
...  
Keyword(s):  
Photonic Band Gap ◽  
Cholesteric Liquid Crystal ◽  
Tight Binding ◽  
Defect Layer ◽  
Solid State Physics ◽  
Tight Binding Approximation ◽  
Defect Modes ◽  
Optical Modes ◽  
Low Threshold ◽  
Photonic Band

Cholesteric liquid crystal structures with multiple isotropic defect layers exhibit localized optical modes (defect modes). Coupling effects between these modes were simulated using the finite difference time domain method. Analogous to the well-known result of the tight-binding approximation in solid state physics, splitting of the defect modes takes place, as soon as the structure contains more than one defect layer. The dispersion relation of the mini-bands forming within the photonic band gap of the structure is calculated numerically. The structures might have promising applications for multiwavelength filters and low-threshold lasers.

Tunable properties of one-dimensional photonic crystals that incorporate a defect layer of a magnetized plasma

2017 ◽  
Vol 31 (31) ◽  
pp. 1750239 ◽  
Author(s):  
Arafa H. Aly ◽  
Hussein A. Elsayed ◽  
Ayman A. Ameen ◽  
S. H. Mohamed
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Plasma Layer ◽  
Photonic Band Gap ◽  
Defect Layer ◽  
Magnetized Plasma ◽  
Characteristic Matrix ◽  
Angle Of Incidence ◽  
One Dimensional ◽  
Photonic Band

In this paper, we theoretically investigate the transmittance characteristics of one-dimensional defective photonic crystal in microwave radiations based on the fundamentals of the characteristic matrix method. Here, the defect layer is magnetized plasma. The numerical results show the appearance of defect peaks inside the Photonic Band Gap. The external magnetic field has a significant effect on the permittivity of the defect layer. Therefore, the position and intensity of the defect peak are strongly affected by the external magnetic field. Moreover, we have investigated the different parameters on the defect peaks as the plasma density, the thickness of the plasma layer and the angle of incidence. Wherefore, the proposed structure could be the cornerstone for many applications in microwave regions such as narrowband filters.

Two-Dimensional Photonic Band-Gap Defect Modes with Deformed Lattice

2005 ◽  
Vol 22 (9) ◽  
pp. 2290-2293 ◽  
Author(s):  
Cai Xiang-Hua ◽  
Zheng Wan-Hua ◽  
Ma Xiao-Tao ◽  
Ren Gang ◽  
Xia Jian-Bai
Keyword(s):  
Band Gap ◽  
Photonic Band Gap ◽  
Two Dimensional ◽  
Defect Modes ◽  
Photonic Band

Optical Properties of Laser Lines and Fluorescent Spectrum in Cholesteric Liquid Crystal Laser

2015 ◽  
Vol 15 (10) ◽  
pp. 7632-7639 ◽  
Author(s):  
Mi-Yun Jeong ◽  
Ki Soo Chung ◽  
J.W. Wu
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Photonic Band Gap ◽  
Cholesteric Liquid Crystal ◽  
Polarized Light ◽  
Lasing Threshold ◽  
Left Handed ◽  
Fluorescent Spectrum ◽  
Photonic Band ◽  
Circular Polarized Light

We experimentally studied the comprehensive optical properties of the laser lines and fluorescent spectrum generated by a continuous tunable cholesteric liquid crystal (CLC) laser array. We found that the laser lines generated from a CLC with a right-handed circular helix were right-handed circular polarized and laser lines generated from a CLC with a left-handed circular helix were left-handed circular polarized. Inside the photonic band gap, the CLC structure with right-(left-) handed helicity suppressed the fluorescence generated with right (left) circular polarized light, and instead the suppressed right (left) circular polarized light energy moved to the outside of the photonic band gap, so we can say that the fluorescence intensity outside of the photonic band gap is enhanced with right (left) handed circular polarized light. Depending on the position of the photonic band gap, the fluorescence quantum yield value increased by up to ∼15%. These enhanced fluorescence intensities at the PBG edge will evolve into lasing at the upper lasing threshold. It is particularly interesting to see that the fluorescence intensity and shape could be controlled by adjusting the external geometrical factor of the photonic band gaps. The lasing threshold of the CLC lasers was in the range of 1.5–5.3 μJ/pulse. For CLC laser device applications, it is necessary and essential to know the optical properties of the generated laser lines and of the fluorescence spectrum.

2-D Photonic Quasicrystal in Metallic Microcavity

2003 ◽  
Vol 797 ◽  
Author(s):  
J. Y. Zhang ◽  
H. L. Tam ◽  
W. H. Wong ◽  
Y. B. Pun ◽  
J. B. Xia ◽  
...  
Keyword(s):  
Photonic Crystal ◽  
Band Gap ◽  
Crystal Structures ◽  
Photonic Band Gap ◽  
Photonic Devices ◽  
Experimental Result ◽  
Photoluminescence Spectra ◽  
Low Threshold ◽  
Photonic Band ◽  
Photonic Quasicrystal

ABSTRACTPhotonic microcavity promises to be one of the photonic devices that can have immediate applications such as super bright LED and low threshold laser. Most photonic crystal structures currently used on microcavity are cubic or hexagonal, whose folding symmetry is no greater than 6. In this work, we fabricated 2-D photonic microcavity with Penrose quasicrystal pattern and measured the angular resolved transmission and photoluminescence spectra of the microcacity. From the experimental result it is found that isotropic photonic band gap exists in the microcavity with the Penrose quasicrystal pattern.

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