scholarly journals Tunable Transmissive Terahertz Linear Polarizer for Arbitrary Linear Incidence Based on Low-Dimensional Metamaterials

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1851
Author(s):  
Zhenyu Yang ◽  
Dahai Yu ◽  
Huiping Zhang ◽  
Anqi Yu ◽  
Xuguang Guo ◽  
...  
Keyword(s):  
Graphene Ribbon ◽  
Polarization Rotation ◽  
Metallic Grating ◽  
Scattering Rate ◽  
Simulation Based ◽  
Linearly Polarized ◽  
Transmission Window ◽  
Low Dimensional ◽  
Linear Polarizer ◽  
Difference Time

In this work, we propose a structure consisting of three metamaterial layers and a metallic grating layer to rotate the polarization of arbitrary linearly polarized incidence to the y-direction with high transmissivity by electrically tuning these metamaterials. The transfer matrix method together with a harmonic oscillator model is adopted to theoretically study the proposed structure. Numerical simulation based on the finite difference time-domain method is performed assuming that the metamaterial layers are constituted by graphene ribbon arrays. The calculation and simulation results show that the Drude absorption is responsible for the polarization rotation. Fermi level and scattering rate of graphene are important for the transmissivity. For a polarization rotation of around 90°, the thickness of either the upper or lower dielectric separations influences the transmission window. For a polarization rotation of around 45° and 135°, the lower dielectric separations decide the frequency of the transmission window, while the upper dielectric separations just slightly influence the transmissivity.

scholarly journals Metasurface of Combined Semicircular Rings with Orthogonal Slit Pairs for Generation of Dual Vector Beams

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1718
Author(s):  
Qian Kong ◽  
Manna Gu ◽  
Xiangyu Zeng ◽  
Rui Sun ◽  
Yuqin Zhang ◽  
...  
Keyword(s):  
Time Domain ◽  
Finite Difference Time Domain ◽  
Polarized Light ◽  
Orientation Angle ◽  
Fdtd Simulation ◽  
Dual Vector ◽  
Vector Beams ◽  
Linearly Polarized ◽  
Potential Applications ◽  
Difference Time

Manipulation of multichannel vector beams (VBs) with metasurfaces is an important topic and holds potential applications in information technology. In this paper, we propose a novel metasurface for the generation of dual VBs, which is composed of orthogonal slit pairs arranged on multiple groups of combined semicircular rings (CSRs). A group of CSRs include a right-shifted set and a left-shifted set of semicircular rings, and each set of semicircular rings has two halves of circles with different radii, sharing the same shifted center. Under the illumination of linearly polarized light, the two shifted sets of semicircular rings generate the two VBs at the shifted center positions on the observation plane. The slit units of each set are designed with independent rotation order and initial orientation angle. By adjusting the linear polarization of illumination, both two VBs with their orders and polarization states are independently controlled simultaneously. The principle and design are demonstrated by the finite-difference time domain (FDTD) simulation. The work is of significance for miniatured devices of VB generators and for related applications.

Investigation of Contact Conditions During Stamping of a Thin Plate

2020 ◽  
Author(s):  
Harshal Y. Shahare ◽  
Rohan Rajput ◽  
Puneet Tandon
Keyword(s):  
Wave Propagation ◽  
Material Properties ◽  
High Speed ◽  
Fdtd Method ◽  
Propagation Model ◽  
Transmitted Wave ◽  
Two Dimensional ◽  
Contact Conditions ◽  
Simulation Based ◽  
Difference Time

Abstract Stamping is one of the most used manufacturing processes, where real-time monitoring is quite difficult due to high speed of the mechanical press, which leads to deterioration of the accuracy of the products In the present work, a method is developed to model elastic waves propagation in solids to measure contact conditions between die and workpiece during stamping. A two-dimensional model is developed that reduces the wave propagation equations to two-dimensional equations. To simulate the wave propagation inside the die-workpiece model, the finite difference time domain (FDTD) method and modified Yee algorithm has been employed. The numerical stability of the wave propagation model is achieved through courant stability condition, i.e., Courant-Friedrichs-Lewy (CFL) number. Two cases, i.e., flat die-workpiece interface and inclined die-workpiece interface, are investigated in the present work. The elastic wave propagation is simulated with a two-dimension (2D) model of the die and workpiece using reflecting boundary conditions for different material properties. The experimental and simulation-based results of reflected and transmitted wave characteristics are compared for different materials in terms of reflected and transmitted wave height ratio and material properties such as acoustic impedance. It is found that the numerical simulation results are in good agreement with the experimental results.

SURFACE PLASMON ENHANCED PHOTOLUMINESCENCE ON BIHARMONIC GRATING STRUCTURE

2010 ◽  
Vol 19 (04) ◽  
pp. 571-581 ◽  
Author(s):  
YASUMASA FUJIWARA ◽  
KOJI MURATA ◽  
MASAYOSHI OJIMA ◽  
YASUHIRO OGAWA ◽  
HITOSHI KUBO ◽  
...  
Keyword(s):  
Surface Plasmon ◽  
Surface Plasmon Polariton ◽  
Fluorescence Enhancement ◽  
Coupling Efficiency ◽  
Sinusoidal Grating ◽  
Short Wavelength Band ◽  
Metallic Grating ◽  
Enhanced Photoluminescence ◽  
Plasmon Polariton ◽  
Difference Time

We compare the fluorescence enhancement from a conducting polymer film placed on top of a sinusoidal and biharmonic metallic grating. On the biharmonic grating, which possesses a surface plasmon polariton band-gap, the enhancement factor was larger than that on a sinusoidal grating, even though the coupling efficiency of the surface plasmon polariton was lower for the biharmonic grating. We investigate the mechanism of fluorescence enhancement numerically by finite difference time domain analyses and attribute the larger fluorescence enhancement to the electric field of the short wavelength band-edge mode extending longer into the dielectric region where the fluorophore is placed.

scholarly journals Nonstandard FDTD Simulation-Based Design of CROW Wavelength Splitters

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Naoki Okada ◽  
James B. Cole ◽  
Shigeki Yamada ◽  
Kensuke Ogawa ◽  
Yoshifumi Katayama
Keyword(s):  
Optical Waveguides ◽  
Optical Devices ◽  
Whispering Gallery Modes ◽  
Fdtd Simulation ◽  
High Q ◽  
Whispering Gallery ◽  
Simulation Based Design ◽  
Simulation Based ◽  
Fdtd Simulations ◽  
Difference Time

The finite-difference time-domain (FDTD) algorithm has been used in simulation-based designs of many optical devices, but it fails to reproduce high-Q whispering gallery modes (WGMs). On the other hand, the nonstandard (NS) FDTD algorithm can accurately compute WGMs and can be used to make simulation-based designs of WGM devices. Wavelength splitters using the coupled resonator optical waveguides (CROWs) based on WGM couplings have recently attracted attention because they are potentially ultracompact. In this paper, we design a CROW wavelength splitter using NS FDTD simulations and demonstrate high interchannel extinction ratios of over 20 dB.

Correlating Ultrasonic Velocity and Porosity Using FDTD Method Based on Random Pores Model

2011 ◽  
Vol 675-677 ◽  
pp. 1221-1224 ◽  
Author(s):  
Y. Zhao ◽  
Zhen Yue Ma ◽  
Li Lin ◽  
X.M. Li ◽  
M.K. Lei
Keyword(s):  
Finite Difference Time Domain ◽  
Ultrasonic Testing ◽  
Transverse Velocity ◽  
Fdtd Method ◽  
Thermal Barrier ◽  
Barrier Coating ◽  
Simulation Based ◽  
Plasma Sprayed ◽  
Difference Time ◽  
Velocity Decrease

Ultrasonic testing porosity of TBC (thermal barrier coating) has been investigated by numerical simulation based on the implementation of FDTD (Finite Difference Time Domain) method for the RPM (random pores model). Numerical simulations of measuring ultrasonic longitudinal and transverse velocities were carried out for the plasma sprayed ZrO2 coatings with porosities ranging from 0.5 % to 4 %. The results show both longitudinal and transverse velocity decrease with the increase of porosity, which is similar to the experimental results in the reference (J. Thermal Spray Technol 12 (2003) 530-535). The investigation proves that the combination of the RPM and FDTD method is available for simulating ultrasonic testing of TBC porosity.

scholarly journals Power scalability of linearly polarized random fiber laser through polarization-rotation-based Raman gain manipulation

2018 ◽  
Vol 26 (18) ◽  
pp. 22894 ◽  
Author(s):  
Jun Ye ◽  
Jiangming Xu ◽  
Jiaxin Song ◽  
Haiyang Xu ◽  
Hanshuo Wu ◽  
...  
Keyword(s):  
Fiber Laser ◽  
Raman Gain ◽  
Polarization Rotation ◽  
Linearly Polarized

scholarly journals Search for sub-eV axion-like resonance states via stimulated quasi-parallel laser collisions with the parameterization including fully asymmetric collisional geometry

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
◽  
Kensuke Homma ◽  
Yuri Kirita ◽  
Masaki Hashida ◽  
Yusuke Hirahara ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Laser Field ◽  
Mass Range ◽  
Vacuum System ◽  
Mass Relation ◽  
Experimental Conditions ◽  
Resonance States ◽  
Scattering Rate ◽  
Linearly Polarized ◽  
Converted Signal

Abstract We have searched for axion-like resonance states by colliding optical photons in a focused laser field (creation beam) by adding another laser field (inducing beam) for stimulation of the resonance decays, where frequency-converted signal photons can be created as a result of stimulated photon-photon scattering via exchanges of axion-like resonances. A quasi-parallel collision system (QPS) in such a focused field allows access to the sub-eV mass range of resonance particles. In past searches in QPS, for simplicity, we interpreted the scattering rate based on an analytically calculable symmetric collision geometry in both incident angles and incident energies by partially implementing the asymmetric nature to meet the actual experimental conditions. In this paper, we present new search results based on a complete parameterization including fully asymmetric collisional geometries. In particular, we combined a linearly polarized creation laser and a circularly polarized inducing laser to match the new parameterization. A 0.10 mJ/31 fs Ti:sapphire laser pulse and a 0.20 mJ/9 ns Nd:YAG laser pulse were spatiotemporally synchronized by sharing a common optical axis and focused into the vacuum system. Under a condition in which atomic background processes were completely negligible, no significant scattering signal was observed at the vacuum pressure of 2.6 × 10−5 Pa, thereby providing upper bounds on the coupling-mass relation by assuming exchanges of scalar and pseudoscalar fields at a 95% confidence level in the sub-eV mass range.

BISTABLE BEHAVIOR OF A KERR LENS MODE LOCKED Ti:SAPPHIRE LASER

2008 ◽  
Vol 18 (06) ◽  
pp. 1719-1726 ◽  
Author(s):  
MARCELO G. KOVALSKY ◽  
ALEJANDRO A. HNILO
Keyword(s):  
Numerical Simulation ◽  
Time Series ◽  
Deterministic Chaos ◽  
Embedding Dimension ◽  
Bistable Behavior ◽  
Ti:Sapphire Laser ◽  
Simulation Based ◽  
Iterative Maps ◽  
Low Dimensional ◽  
Structurally Stable

Kerr lens mode locked Ti :Sapphire lasers can operate in at least two pulsed modes. Several models were developed with the aim to describe the characteristics of these modes. Those based on iterative maps, can reproduce the structurally stable properties of each mode but are unable to describe the interaction between modes. In this paper, we present a numerical simulation based on a complete map equation that makes possible to accurately describe the bistability experimentally observed in the laser. With the numerical time series we determine that the bistable behavior corresponds to low dimensional deterministic chaos and calculate that the embedding dimension of the attractor is three.

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