Abstract-Three-dimensional metacrystals with a broadband isotropic diamagnetic response and an all-angle negative index of refraction

Su Xu, Jian-Bin Liu, Hao Wang, Ci-Kang Su, Hong-Bo Sun,

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-44-4-927&origin=search

Metamaterials (MMs) and photonic crystals (PhCs) exhibiting artificially engineered physical properties have been widely studied in the past decade. However, abnormal properties could only be proposed under a limited range of polarization and directions in most of the previous studies. It is still a challenge to realize an isotropic artificial material with multiple exotic electromagnetic properties. Here we report a three-dimensional metacrystal supporting full polarization and omni-directional incidence. The center-symmetric unit cell consists of non-resonant closed metallic loops on each surface of the dielectric cube. With the cross-scale dispersion engineering, the metacrystal can exhibit an isotropic diamagnetic response and an all-angle negative index of refraction simultaneously at the opposite sides of the MM-PhC transition region. An additional numerical analysis shows the good performance in terahertz and mid-infrared frequencies, which indicates its potential applications on multi-functional optical components with wide polarization-and-direction allowance.

© 2019 Optical Society of America

Abstract-Tunable THz generalized Weyl points

Zhiping Yin, Fujia Chen, Kai Guo, Fei Shen, Keya Zhou, Jun Gao, Shutian Liu, and Zhongyi Guo

Fig. 1 Realization of Weyl points in a synthetic space. (a) Photonic crystals (PCs) with different p, q values. p and q form a parameter space, which determines the geometric structure of PCs. The inset shows one unit cell of the PC, where the first and the third layers are made of 5CB LCs (cyan), and the second and the forth layers are made of PDMS (gray). The thickness of each layer is related to its position in the p-q parameter space. (b) The band dispersion of PCs with two layers in one unit cell (red dash line) and four layers in one unit cell (blue solid line). Crossing points appear inside four layers’ dispersion. Here, 𝑑𝑎=125𝑢𝑚,$d_a=125um,$ 𝑑𝑏=35𝑢𝑚,$d_b=35um,$ and 𝑝=𝑞=0.$p=q=0.$ (c) The dispersion of PCs in the p-q space with 𝑘=0.5𝑘0,$k=0.5k_0,$ and 𝑘0=𝜋/(𝑑𝑎+𝑑𝑏).$k_0=\pi /\left(d_a+d_b\right).$ Here, two bands form a conical intersection. Panels (b) and (c) together show that the band dispersions are linear in all directions around the degenerated point in synthetic space, so we call it generalized Weyl point. (d) The equal frequency contours around generalized Weyl point in p-q space and its charge “-1”.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-2-512

Weyl points, as linearly double degenerated point of band structures, have been extensively researched in electronic and classical wave systems. However, Weyl points’ realization is always accompanied with delicate “lattice structures”. In this work, frequency-tunable terahertz (THz) generalized Weyl points inside the parameter space have been investigated and displayed by a specially designed photonic crystal with polydimethylsiloxane (PDMS) immersed in 4-cyano’-pentylbipenyl (5CB) liquid crystals (LCs). The reflective phase vortices as a signature of the generalized Weyl points are observed through our numerically simulations. Besides, interface states between photonic crystals and any reflective substrates are fulfilled too. Meanwhile, we could also change the orientation of LC molecule by the external magnetic field so as to tune the frequency of the first two bands’ Weyl point from 0.27698THz to 0.30013THz. This band lies in the short-range wireless communication. Thus, our proposal may be beneficial to the investigation and application of Weyl points’ properties and strongly localized states.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Broadband terahertz ZnO photonic crystals fabricated by 3D printing

Carmen R.Tubío, José Antonio Nóvoa, Jorge Martín, Francisco Guitián, José Ramón Salgueiro, Alvaro Gil, 

https://www.sciencedirect.com/science/article/pii/S0272884218334837

ZnO has been demonstrated to be a promising material for optoelectronic applications in the terahertz (THz) spectral range. However, there have been no reports regarding the fabrication of ZnO structures to control THz radiation, as photonic crystal (PCs) materials. Here, we focus on the development of a functional ZnO PCs for the THz band. The functionality is provided by the design that is based on a woodpile lattice with the appropriate periodicity for the THz region. Using a three-dimensional (3D) printing technique, we fabricate 3D ZnO based PCs with an effective lattice constant to generate a bandgap at the THz region. The functionality of the resulting PC was evaluated using THz time-domain spectroscopy combined with theoretical simulations. The results demonstrate the 3D woodpile lattice structure has good optical properties in the THz frequency region. These results serve as a step for the development of new THz functional devices for optoelectronics applications.

Abstract-Synchronized time-coupling theory of resonant mode splitting phenomena in a superconducting photonic crystal at terahertz

Tingting Bian,Chien-Jang Wu,



https://www.sciencedirect.com/science/article/pii/S0030402618309914

Resonant mode splitting phenomenon can be observed in the terahertz transmission spectrum of a finite superconducting photonic crystal (SD)NS, where S and D denote a superconducting layer and a dielectric layer, respectively. In this structure, each D-layer in (SD)NS constitutes a Fabry-Perot cavity. The original single resonant mode at N = 1 can then be split into N resonant modes for N > 1 due to the time-coupling effect coming from Ncavities. Within the framework of the coupled mode theory, we successfully employ synchronized time-coupling theory to analytically explain the number of split resonant peaks, the resonant frequencies, and the frequency intervals between peaks. Additionally, it is found that the coupling coefficient is an increasing function of the original resonant frequency, which, in turn, indicates that the split frequencies and interval can be tuned by the thickness of layer D. Application of this synchronized time-coupling theory to elucidate similar splitting phenomena in plasma photonic crystals and metamaterial photonic crystals is also discussed.

Abstract-A Modularized and Switchable Component for Flexible Passive Device: Terahertz Photonic Crystals with Fine‐Tuning

Jiannan Gao, Rong Wang, Qian Zhao, Bo Li, Ji Zhou,




https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.201800384?af=R

In this work, tunable terahertz photonic crystals (PCs) used as modularized and switchable components in flexible passive device are designed and prepared. Flexible woodpile structures created by the direct‐writing technology with a composite ink system composed of barium strontium titanate nanoparticles and polydimethylsiloxane are immersed in 5CB liquid crystals (LCs), where the orientation of LC molecule is modulated by the external magnetic field. Each of these can work in terahertz wavelength with specific position and depth of the dips in the transmittance spectra due to different geometries as well as having the ability of fine‐tuning. Experiments show that the photonic gaps of these PCs can cover from 0.2 to 0.3 THz, as well as about 7.5% fine tunability of photonic gap appearing with the orientation change of the magnetic field. More interestingly, the dips of photonic gaps keep the same position but become deeper with the increase of layer, an ability to realize another dimensional switchover. This work demonstrates that efficient terahertz PCs with different geometry parameters could be dynamically tuned by the orientation of magnetic field and it can open a universal approach to shrinking the size of device and rapid manufacturing in a large throughput.

Abstract-Design and analysis of novel microstrip patch antenna on photonic crystal in THz

Ritesh Kumar Kushwahaa,  P. Karrupanana, L.D. Malviyab,

https://www.sciencedirect.com/science/article/pii/S0921452618303855

Recent advancement of communication system requires low cost, minimal weight, low profile and high-performance antenna to execute the demand of the future realization. A high gain novel microstrip patch antenna design is proposed, based on the photonic crystal for terahertz (THz) spectral band applications. This antenna is mounted on polyimide substrate that employs Photonic Band Gap (PBG) crystal and the Gain of 7.934 dB, Directivity 8.612 dBi and VSWR close to unity at resonant frequency of 0.6308 THz. The proposed antenna model is compared with homogeneous polyimide substrate structure based microstrip patch antenna and analyzed the radiation characteristics. Moreover, the performance of designed antenna is investigated with different PBG cylindrical distance, PBG hole radius, curvature radius of patch and substrate heights. The projected design antenna has a bandwidth of 36.25 GHz and −10 dB impedance with operating frequency range varying from 0.6152 THz to 0.6514 THz, hence it can be utilized for detection of explosive and material characterization applications.

Abstract-One-way edge modes in a photonic crystal of semiconductor at terahertz frequencies

Lingjuan He, Qian Shen, Jie Xu, Yun You, Tianbao Yu, Linfang Shen, Xiaohua Deng,

https://www.nature.com/articles/s41598-018-26395-4

Electromagnetic edge mode in a photonic crystal (PhC), which is a square array of semiconductor rods in air, is theoretically investigated for terahertz frequencies. In the PhC, gyroelectric anisotropy is introduced in the semiconductor rods by applying an external magnetic field and consequently, a degeneracy point, at which two dispersion surfaces intersect, is lifted and a new band gap is created. The edge mode sustained by the PhC possesses the character of one-way propagation, and it even can be immune to backscattering at large defect on the wavelength scale and 90° sharp bend. The properties of the one-way mode are closely dependent on the cladding layer structure of the PhC.

Abstract-Terahertz Tag Using Photonic-Crystal Slabs

 Yusuke Kujime,  Masayuki Fujita, Tadao Nagatsuma

https://ieeexplore.ieee.org/document/8337729/

To realize the concept of the Internet of Everything (IoE), which has attracted significant interest, information tags directly attached to objects constitute one of the key technologies. However, in terms of security and uniqueness, the current information tags are unsatisfactory. In this paper, we propose the use of terahertz (THz) tags, which are expected to reduce these concerns, toward future IoE applications. In place of the usual small-capacity THz tags, we propose large-capacity THz tags utilizing both frequency and spatial domains by using two-dimensional photonic-crystal slabs in a matrix. We discuss the numerical analysis of photonic-crystal slabs for THz tags; for instance, the electric fields in photonic-crystal slabs at an absorption frequency and the characteristics of photonic-crystal slabs are detailed. Finally, we describe the successful demonstration of a THz tag with a capacity of 48 bit/cm2 in the 600-GHz band, which is almost four times the capacity of previous THz tags.

Abstract-Application 43 – Development of Photonic Crystal Resonators for Terahertz Wave Sensing by Using Nanoparticle Stereolithography

Soshu Kirihara

https://www.blogger.com/blogger.g?blogID=124073320791841682#editor/target=post;postID=1548959674798218270

Photonic crystals with periodic variations in dielectric constants can exhibit forbidden gaps in transmission spectrum to totally reflect electromagnetic waves through Bragg diffraction (Yablonovitch, 1987). Through introductions of artificial defects of air cavities into the periodic arrangement, localized modes are formed in the photonic bandgaps. These structural defects can localize and amplify electromagnetic wave energies at the specific frequencies and wavelengths corresponding to the sizes and dielectric constants of the resonation domains. For the last few decades, the photonic crystal has been expected to be applied for various microwave devices of resonators, filters, and directional antennas (Noda, 2000). Especially, micrometer order ceramic lattices with diamond structures were fabricated successfully by using nanoparticle stereolithography to create the perfect photonic bandgaps and reflect the electromagnetic waves totally in all directions (Kirihara and Miyamoto, 2009). The lattice constant of the diamond structure and the aspect ratio of the dielectric lattice were designed as 500 μm and 1.5, respectively. The whole size of the crystal component was 5 mm × 5 mm × 1 mm consisting of 10 × 10 × 2 unit cells. Fig. 43.1 shows a schematic illustration of the stereolithography system. Photosensitive acrylic resins including alumina particles of 170 nm in average diameter at 40% in volume content were supplied on a glass substrate from a dispenser nozzle by the air pressure. This paste was spread uniformly by using a mechanically controlled knife edge. The thickness of each layer was set at 15 μm. Two-dimensional solid patterns are obtained by a light-induced photopolymerization. High-resolution image has been achieved by using a digital micromirror device. In this optical device, microaluminum mirrors of 14 μm in edge length were assembled with 1024 × 768 in numbers. Each mirror can be tilted independently by piezoelectric actuating. Through the layer stacking, the acrylic resin component with the alumina particle dispersion was obtained. The composite precursor was dewaxed at 600°C for 2 h and sintered at 1500°C for 2 h in the air atmosphere. Fig. 43.2 shows the alumina lattice with the diamond structure fabricated by ceramic powder sintering. No cracks or deformations were observed in the obtained components. The average linear shrinkage was 25%. The lattice constant of the sintered sample was 375 μm. The relative density of the sample reached 97.5%.

Abstract-Terahertz tunable reflectance of extrinsic photonic crystals by external magnetic field

• Sahar A. El-Naggar

https://link.springer.com/article/10.1140%2Fepjd%2Fe2017-80585-7

In this work, we theoretically investigate the reflectance of an extrinsic photonic crystal (PC) which is composed of bulk semiconductor (InSb) under the effect of a spatially periodic magnetic field. We consider the magneto-optical effect where the magnetic field is parallel to the direction of wave propagation (Faraday effect). In addition, we take into account the lossy nature of InSb. Numerical results which have been conducted by the transfer matrix method show that our structure behaves like conventional PC with switchable electromagnetic band gaps. We show that our structure can be used as a tunable reflector that has the advantages of being tunable by the magnetic field and it fits to work in terahertz frequency range

Abstract-A Tunable Eight-Wavelength Terahertz Modulator Based on Photonic Crystals

K. Ji, H. Chen, W. Zhou, Y. Zhuang, J. Wang

https://link.springer.com/article/10.1007%2Fs10812-017-0551-y


We propose a tunable eight-wavelength terahertz modulator based on a structure of triple triangular lattice photonic crystals by using photonic crystals in the terahertz regime. The triple triangular lattice was formed by nesting circular, square, and triangular dielectric cylinders. Three square point defects were introduced into the perfect photonic crystal to produce eight defect modes. GaAs was used as the point defects to realize tunability. We used a structure with a reflecting barrier to achieve modulation at high transmission rate. The insertion loss and extinction ratio were 0.122 and 38.54 dB, respectively. The modulation rate was 0.788 dB. The performance of the eightwavelength terahertz modulator showed great potential for use in future terahertz communication systems.

Abstract-One-dimensional multiband terahertz graphene photonic crystal filters

Yizhe Li, Limei Qi, Junsheng Yu, Zhijiao Chen, Yuan Yao, and Xiaoming Liu

https://www.osapublishing.org/ome/abstract.cfm?uri=ome-7-4-1228&origin=search

Properties of one-dimensional graphene photonic crystals with dual-layer defects are studied. Results show that two defect modes appear within the gaps, and the defect modes shift to the lower frequencies with the chemical potential increasing, the physical mechanism are also given based on the relative dielectric constant of the graphene. It is also found that the frequency, magnitude, and numbers of the defect modes can vary with the symmetrical changes of the dual-defect layers. For oblique incidence, the defect modes of the TE polarization follow a similar trend with the TM polarization, and all the defect modes shift to the higher frequencies and disappear while new defect modes appear at the larger incident angles. These properties of graphene photonic crystals with dual-layer defects have potential applications in tunable terahertz narrow multiband filters.

© 2017 Optical Society of America

Abstract-Large caliber array type terahertz wave generating device having photonic crystal structure

United States Patent 9761750
Inventors:
Moon, Ki Won (Daejeon, KR) 
Park, Kyung Hyun (Daejeon, KR) 

http://www.freepatentsonline.com/9761750.html

Provided herein is a large caliber terahertz wave generating device having a photonic crystal structure. The device includes a first electrode and a second electrode. The first electrode includes a first line pattern extending in a first direction, second line patterns coupled to the first line pattern and extending in a second direction, and third line patterns which are coupled to the first line pattern, extend in the second direction, are disposed between the second line patterns, and are longer than the second line patterns. The second electrode includes a fourth line pattern which extends in the first direction, fifth line patterns coupled to the fourth line pattern and extending in the second direction, and sixth line patterns which are coupled to the fourth line pattern, extend in the second direction, are disposed between the fifth line patterns, and are longer than the fifth line patterns.