scholarly journals Broadband Anisotropy in Terahertz Metamaterial With Single-Layer Gap Ring Array

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2255 ◽  
Author(s):  
Liangping Xia ◽  
Hong-Liang Cui ◽  
Man Zhang ◽  
Suihu Dang ◽  
Chunlei Du
Keyword(s):  
Femtosecond Laser ◽  
Theoretical Prediction ◽  
Time Domain ◽  
Single Layer ◽  
Terahertz Waves ◽  
System A ◽  
Resonant Modes ◽  
Metallic Ring ◽  
Terahertz Transmission ◽  
Anisotropic Metamaterial

To convert the polarization of terahertz waves pumped by a femtosecond laser in a terahertz time domain system, a broadband anisotropic metamaterial is proposed. The metamaterial is constructed with a single-layer gapped metallic ring array, which supports different resonant modes in orthogonal directions. With the aid of simulations and measurements, the anisotropy of the terahertz transmission is demonstrated and discussed. The experimental results of THz transmission in the metamaterial indicate that the anisotropic band is as wide as 0.56 THz, which accords well with our theoretical prediction.

Effect of Zn incorporation on physical properties of quaternary 0.7Se–0.2Ge–(0.1-x)Sb–xZn chalcogenide system: A theoretical prediction

2021 ◽  
Vol 612 ◽  
pp. 412896
Author(s):  
Rittwick Mondal ◽  
Yumnam Bonney Singh ◽  
Anindya Sundar Das ◽  
Soumyajyoti Kabi ◽  
Loitongbam Surajkumar Singh ◽  
...  
Keyword(s):  
Theoretical Prediction ◽  
Physical Properties ◽  
System A

Fabrication of Three-Dimensional Micro-Structures with Two-Photon Absorption by Femtosecond Laser

2006 ◽  
Vol 532-533 ◽  
pp. 568-571
Author(s):  
Ming Zhou ◽  
Hai Feng Yang ◽  
Li Peng Liu ◽  
Lan Cai
Keyword(s):  
Photonic Crystal ◽  
Femtosecond Laser ◽  
Detection System ◽  
Three Dimensional ◽  
Photon Absorption ◽  
Micro Fabrication ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Photo Polymerization ◽  
System A

The photo-polymerization induced by Two-Photon Absorption (TPA) is tightly confined in the focus because the efficiency of TPA is proportional to the square of intensity. Three-dimensional (3D) micro-fabrication can be achieved by controlling the movement of the focus. Based on this theory, a system for 3D-micro-fabrication with femtosecond laser is proposed. The system consists of a laser system, a microscope system, a real-time detection system and a 3D-movement system, etc. The precision of micro-machining reaches a level down to 700nm linewidth. The line width was inversely proportional to the fabrication speed, but proportional to laser power and NA. The experiment results were simulated, beam waist of 0.413μm and TPA cross section of 2×10-54cm4s was obtained. While we tried to optimize parameters, we also did some research about its applications. With TPA photo-polymerization by means of our experimental system, 3D photonic crystal of wood-pile structure twelve layers and photonic crystal fiber are manufactured. These results proved that the micro-fabrication system of TPA can not only obtain the resolution down to sub-micron level, but also realize real 3D micro-fabrication.

Time-domain properties of femtosecond laser diffracted by ‘surface-volume-surface’ gratings

2018 ◽  
Vol 15 (12) ◽  
pp. 125301
Author(s):  
Chongchong Han ◽  
Fan Gao ◽  
Xiang Zhang ◽  
Xiao Yuan
Keyword(s):  
Femtosecond Laser ◽  
Time Domain

scholarly journals Electrically Tunable Broadband Terahertz Absorption with Hybrid-Patterned Graphene Metasurfaces

Nanomaterials ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 562 ◽  
Author(s):  
Longfang Ye ◽  
Xin Chen ◽  
Guoxiong Cai ◽  
Jinfeng Zhu ◽  
Na Liu ◽  
...  
Keyword(s):  
Incident Angle ◽  
Single Layer ◽  
Normal Incidence ◽  
Transverse Magnetic ◽  
Single Layer Graphene ◽  
Terahertz Waves ◽  
Broadband Absorption ◽  
Terahertz Sensing ◽  
Axisymmetric Configuration ◽  
Broadband Terahertz

We numerically demonstrate a broadband terahertz (THz) absorber that is based on a hybrid-patterned graphene metasurface with excellent properties of polarization insensitivity, wide-angle, and active tunability. Our design is made up of a single-layer graphene with periodically arranged hybrid square/disk/loop patterns on a multilayer structure. We find that broadband absorption with 90% terahertz absorbance and the fractional bandwidth of 84.5% from 1.38 THz to 3.4 THz can be achieved. Because of the axisymmetric configuration, the absorber demonstrates absolute polarization independence for both transverse electric (TE) and transverse magnetic (TM) polarized terahertz waves under normal incidence. We also show that a bandwidth of 60% absorbance still remains 2.7 THz, ranging from 1.3 THz to 4 THz, for a wide incident angle ranging from 0° to 60°. Finally, we find that by changing the graphene Fermi energy from 0.7 eV to 0 eV, the absorbance of the absorbers can be easily tuned from more than 90% to lower than 20%. The proposed absorber may have promising applications in terahertz sensing, detecting, imaging, and cloaking.

Bandwidth improvement of planar antennas using a single-layer metamaterial substrate for X-band application

2020 ◽  
Vol 12 (9) ◽  
pp. 906-914
Author(s):  
O. Borazjani ◽  
M. Naser-Moghadasi ◽  
J. Rashed-Mohassel ◽  
R. A. Sadeghzadeh
Keyword(s):  
Microstrip Antenna ◽  
Single Layer ◽  
Dual Band ◽  
Planar Antennas ◽  
Radiation Characteristics ◽  
Dual Band Antenna ◽  
X Band ◽  
Field Radiation ◽  
Metallic Ring ◽  
Good Agreement

AbstractTo prevent far-field radiation characteristics degradation while increasing bandwidth, an attempt has been made to design and fabricate a microstrip antenna. An electromagnetic band gap (EBG) structure, including a layer of a metallic ring on a layer of Rogers 4003C substrate, is used. For a better design, a patch antenna with and without the EBG substrate has been simulated. The results show that the bandwidth can be improved up to 1.6 GHz in X-band by adding the EBG substrate. Furthermore, using this structure, a dual-band antenna was obtained as well. Finally, to validate the simulation results, a comparison has been done between simulation data and experimental results which demonstrate good agreement.

Resonant Control of a Single-Link Flexible Manipulator

2014 ◽  
Vol 67 (5) ◽  
Author(s):  
Auwalu M. Abdullahi ◽  
Z. Mohamed ◽  
Marwan Nafea M.
Keyword(s):  
Feedback Control ◽  
Flexible Manipulator ◽  
Control Loop ◽  
Vibration Effect ◽  
System A ◽  
Resonant Modes ◽  
Single Link ◽  
Integral Controller ◽  
Proportional Integral Controller ◽  
Resonant Control

This paper presents resonant control of a single-link flexible manipulator based on the resonant modes frequencies of the system. A flexible manipulator system is a single-input multi-output (SIMO) system with motor torque as an input and hub angle and the tip deflection as outputs. The previous system which is modeled using the finite element method is considered, and the resonant modes of the system are determined. Two negative feedback controllers are used to control the system. The inner feedback control loop designed using the resonant frequencies adds damping to the system and suppress the vibration effect around the hub angle. For the outer feedback control loop, a proportional integral controller is designed to achieve a zero steady state error so that a precise tip positioning can be achieved. Simulation results are presented and discussed to show the effectiveness of the resonant control scheme. 

scholarly journals A novel case using femtosecond laser-acquired lenticule for recurrent pterygium: case report and literature review

2018 ◽  
Vol 46 (6) ◽  
pp. 2474-2480 ◽  
Author(s):  
Om Prakash Pant ◽  
Ji-long Hao ◽  
Dan-dan Zhou ◽  
Fan Wang ◽  
Cheng-wei Lu
Keyword(s):  
Femtosecond Laser ◽  
Corneal Thickness ◽  
Anterior Segment ◽  
Single Layer ◽  
Cost Effective ◽  
Laser Technique ◽  
First Case ◽  
Lenticule Extraction ◽  
Recurrent Pterygium ◽  
Thin Cornea

Small incision lenticule extraction (SMILE) is a minimally invasive, safe and flapless femtosecond laser technique used mainly to correct myopia through extraction of a corneal lenticule. Lenticules obtained in this way are transparent and of high quality, and thus, can be used to treat other corneal diseases. A 65-year-old male patient presented with recurrent pterygium complicated by thin cornea. The patient was treated surgically using a SMILE-extracted lenticule to avoid further complications and to maintain eyeball integrity. The lenticule was sutured over the thin section of cornea using 10-0 interrupted nylon sutures and enclosed by a single layer of amniotic membrane. The patient was evaluated using slit-lamp biomicroscopy and anterior-segment optical-coherence tomography. During an 8-month follow-up, the graft remained intact with no sign of rejection and corneal thickness was maintained. Tectonic keratoplasty using a SMILE-extracted lenticule appears to be a safe, cost-effective and reliable method for treating thin cornea due to repeated surgeries for recurrent pterygium. This is the first case of recurrent pterygium complicated by thin cornea managed surgically using a SMILE-extracted lenticule.

scholarly journals Terahertz Time-Domain Polarimetry in Reflection for Film Characterization

Sensors ◽  
2020 ◽  
Vol 20 (12) ◽  
pp. 3352
Author(s):  
Sandrine van Frank ◽  
Elisabeth Leiss-Holzinger ◽  
Michael Pfleger ◽  
Christian Rankl
Keyword(s):  
Optical Properties ◽  
Time Domain ◽  
Terahertz Spectroscopy ◽  
Single Layer ◽  
Measured Signal ◽  
Terahertz Time Domain Spectroscopy ◽  
Wide Range ◽  
Reflection Geometry ◽  
Layer Thin Film ◽  
Good Agreement

Terahertz time-domain spectroscopy is a useful technique to characterize layered samples and thin films. It gives access to their optical properties and thickness. Such measurements are done in transmission, which requires access to the sample from opposite sides. In reality this is not always possible. In such cases, reflection measurements are the only option, but they are more difficult to implement. Here we propose a method to characterize films in reflection geometry using a polarimetric approach based on the identification of Brewster angle and modeling of the measured signal to extract the refractive index and thickness of the sample. The technique is demonstrated experimentally on an unsupported single layer thin film sample. The extracted optical properties and thickness were in good agreement with established transmission terahertz spectroscopy measurements. The new method has the potential to cover a wide range of applications, both for research and industrial purposes.

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