Investigation of defective hybrid cladding with silicon nanocrystal PCF for supercontinuum generation

Laser Physics ◽  
2021 ◽  
Vol 31 (12) ◽  
pp. 126206
Author(s):  
A Rajesh ◽  
S Chandru ◽  
S Robinson
Keyword(s):  
Pump Power ◽  
Group Velocity Dispersion ◽  
Structural Parameters ◽  
Hybrid Approach ◽  
Silicon Nanocrystal ◽  
Negative Dispersion ◽  
High Nonlinearity ◽  
High Pump Power ◽  
The Impact ◽  
Air Hole

Abstract Defective hybrid cladding through a silicon nanocrystal-core-structured photonic crystal fiber intended for high pump power supercontinuum proliferation is discussed in this paper. The cladding comprehends a hybrid approach of a hexagonal air hole in the outer section and a petal-structured air hole in the inner layer with a twisted pattern. Such a procedure with an air hole in the cladding section with a silicon nanocore displays high nonlinearity and negative dispersion at the communication window for varying pulse widths with 20 kW pump power. The impact of structural parameters of the proposed structure on the optical constraints is discussed, namely, dispersion, nonlinearity and group-velocity dispersion for wavelengths ranging from 0.45 µm to 1.85 µm. The proposed structure with optimized structural parameters provides high nonlinearity of about 6.38 × 106 W−1 km−1 with negative dispersion of −70.19 ps (nm km)−1 at 1550 nm.

Dispersion engineering of a As2Se3-based strip/slot hybrid waveguide for mid-infrared broadband wavelength conversion

2016 ◽  
Vol 30 (28) ◽  
pp. 1650336 ◽  
Author(s):  
Zhanqiang Hui ◽  
Lingxuan Zhang ◽  
Leiran Wang ◽  
Wenfu Zhang
Keyword(s):  
Conversion Efficiency ◽  
Wavelength Conversion ◽  
Group Velocity Dispersion ◽  
Structural Parameters ◽  
Nonlinear Coefficient ◽  
Effective Area ◽  
Wavelength Converter ◽  
Mid Infrared ◽  
Hybrid Waveguide ◽  
The Impact

An arsenic tri-selenide-based strip/slot hybrid waveguide with a single horizontal silica slot is proposed to achieve an extremely low and flat dispersion with three zero dispersion wavelengths. By adjusting the geometrical structural parameters of the hybrid waveguide, dispersion tailoring is fully obtained. The flat group velocity dispersion varying between ±[Formula: see text]0.08 ps2/(m) is obtained over a 1253 nm bandwidth. The parameters of effective area, nonlinear coefficient, and third-order dispersion are all investigated. Moreover, a compact on-chip all-optical wavelength converter is designed based on degenerate four-wave mixing in this waveguide. The dependencies of conversion efficiency and conversion bandwidth on the pump wavelength are discussed. The impact of pump power and signal power on the conversion efficiency is also investigated. The results show that a maximal conversion efficiency of −0.46 dB, and a 3-dB conversion bandwidth of 830 nm in the mid-infrared is achieved.

scholarly journals PCF Design With Extremely High Nonlinearity And Extremely Negative Dispersion

2021 ◽  
Author(s):  
Sanat Kumar Pandey ◽  
J.B. Maurya ◽  
Yogendra Kumar Prajapati
Keyword(s):  
Numerical Aperture ◽  
Effective Area ◽  
Confinement Loss ◽  
Performance Parameters ◽  
Material Loss ◽  
Crystal Fiber ◽  
Negative Dispersion ◽  
High Nonlinearity ◽  
Very High ◽  
Air Hole

Abstract In this manuscript we designed a circular photonic crystal fiber (PCF) having three rectangular holes filled with GaP in the core region, three air hole rings and one annular air ring in cladding region. We found highest negative dispersion for the 1.8µm pitch alongwith very low confinement loss at wavelength 1.55µm. This designed PCF offers high nonlinearity (39612 W-1km-1) and high negative dispersion (-6586 ps nm-1 km-1) alongwith zero confinement loss at 1.55µm wavelength. We also compared the proposed PCF with the previously published PCF structure and found that the nonlinearity and negative dispersion of the designed PCF are very high in comparison to circular air hole based PCF. Another performance parameters viz. birefringence, numerical aperture, effective area and effective material loss are also analyzed.

scholarly journals Design of an Ultrahigh Birefringence Photonic Crystal Fiber with Large Nonlinearity Using All Circular Air Holes for a Fiber-Optic Transmission System

Photonics ◽  
2018 ◽  
Vol 5 (3) ◽  
pp. 26 ◽  
Author(s):  
Shovasis Biswas ◽  
S. Islam ◽  
Md. Islam ◽  
Mohammad Mia ◽  
Summit Sayem ◽  
...  
Keyword(s):  
Photonic Crystal ◽  
Photonic Crystal Fiber ◽  
Nonlinear Coefficient ◽  
Excitation Wavelength ◽  
Crystal Fiber ◽  
Negative Dispersion ◽  
High Nonlinearity ◽  
Fiber Fabrication ◽  
Vector Finite Element ◽  
Air Hole

This paper proposes a hexagonal photonic crystal fiber (H-PCF) structure with all circular air holes in order to simultaneously achieve ultrahigh birefringence and high nonlinearity. The H-PCF design consists of an asymmetric core region, where one air hole is a reduced diameter and the air hole in its opposite vertex is omitted. The light-guiding properties of the proposed H-PCF structure were studied using the full-vector finite element method (FEM) with a circular perfectly matched layer (PML). The simulation results showed that the proposed H-PCF exhibits an ultrahigh birefringence of 3.87 × 10−2, a negative dispersion coefficient of −753.2 ps/(nm km), and a nonlinear coefficient of 96.51 W−1 km−1 at an excitation wavelength of 1550 nm. The major advantage of our H-PCF design is that it provides these desirable modal properties without using any non-circular air holes in the core and cladding region, thus making the fiber fabrication process much easier. The ultrahigh birefringence, large negative dispersion, and high nonlinearity of our designed H-PCF make it a very suitable candidate for optical backpropagation applications, which is a scheme for the simultaneous dispersion and nonlinearity compensation of optical-fiber transmission links.

Are e-learning Webinars the future of medical education? An exploratory study of a disruptive innovation in the COVID-19 era

2020 ◽  
pp. 1-10
Author(s):  
Colin J. McMahon ◽  
Justin T. Tretter ◽  
Theresa Faulkner ◽  
R. Krishna Kumar ◽  
Andrew N. Redington ◽  
...  
Keyword(s):  
Deep Learning ◽  
Carbon Footprint ◽  
Quantitative Research ◽  
Survey Design ◽  
Hybrid Approach ◽  
Disruptive Innovation ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
E Learning ◽  
The Impact

Abstract Objective: This study investigated the impact of the Webinar on deep human learning of CHD. Materials and methods: This cross-sectional survey design study used an open and closed-ended questionnaire to assess the impact of the Webinar on deep learning of topical areas within the management of the post-operative tetralogy of Fallot patients. This was a quantitative research methodology using descriptive statistical analyses with a sequential explanatory design. Results: One thousand-three-hundred and seventy-four participants from 100 countries on 6 continents joined the Webinar, 557 (40%) of whom completed the questionnaire. Over 70% of participants reported that they “agreed” or “strongly agreed” that the Webinar format promoted deep learning for each of the topics compared to other standard learning methods (textbook and journal learning). Two-thirds expressed a preference for attending a Webinar rather than an international conference. Over 80% of participants highlighted significant barriers to attending conferences including cost (79%), distance to travel (49%), time commitment (51%), and family commitments (35%). Strengths of the Webinar included expertise, concise high-quality presentations often discussing contentious issues, and the platform quality. The main weakness was a limited time for questions. Just over 53% expressed a concern for the carbon footprint involved in attending conferences and preferred to attend a Webinar. Conclusion: E-learning Webinars represent a disruptive innovation, which promotes deep learning, greater multidisciplinary participation, and greater attendee satisfaction with fewer barriers to participation. Although Webinars will never fully replace conferences, a hybrid approach may reduce the need for conferencing, reduce carbon footprint. and promote a “sustainable academia”.

scholarly journals Droplet impact onto a spring-supported plate: analysis and simulations

2021 ◽  
Vol 128 (1) ◽  
Author(s):  
Michael J. Negus ◽  
Matthew R. Moore ◽  
James M. Oliver ◽  
Radu Cimpeanu
Keyword(s):  
High Speed ◽  
Flexible Substrate ◽  
Practical Importance ◽  
Hybrid Approach ◽  
Hydrodynamic Pressure ◽  
Analytical Framework ◽  
Canonical System ◽  
Linear Process ◽  
Plate Motion ◽  
The Impact

AbstractThe high-speed impact of a droplet onto a flexible substrate is a highly non-linear process of practical importance, which poses formidable modelling challenges in the context of fluid–structure interaction. We present two approaches aimed at investigating the canonical system of a droplet impacting onto a rigid plate supported by a spring and a dashpot: matched asymptotic expansions and direct numerical simulation (DNS). In the former, we derive a generalisation of inviscid Wagner theory to approximate the flow behaviour during the early stages of the impact. In the latter, we perform detailed DNS designed to validate the analytical framework, as well as provide insight into later times beyond the reach of the proposed analytical model. Drawing from both methods, we observe the strong influence that the mass of the plate, resistance of the dashpot, and stiffness of the spring have on the motion of the solid, which undergo forced damped oscillations. Furthermore, we examine how the plate motion affects the dynamics of the droplet, predominantly through altering its internal hydrodynamic pressure distribution. We build on the interplay between these techniques, demonstrating that a hybrid approach leads to improved model and computational development, as well as result interpretation, across multiple length and time scales.

scholarly journals Offensive keyword extraction based on the attention mechanism of BERT and the eigenvector centrality using a graph representation

2021 ◽  
Author(s):  
Gretel Liz De la Peña Sarracén ◽  
Paolo Rosso
Keyword(s):  
Language Model ◽  
Hybrid Approach ◽  
Attention Mechanism ◽  
Graph Representation ◽  
Keyword Extraction ◽  
Eigenvector Centrality ◽  
Model Learning ◽  
Harmful Content ◽  
The Impact ◽  
Offensive Language

AbstractThe proliferation of harmful content on social media affects a large part of the user community. Therefore, several approaches have emerged to control this phenomenon automatically. However, this is still a quite challenging task. In this paper, we explore the offensive language as a particular case of harmful content and focus our study in the analysis of keywords in available datasets composed of offensive tweets. Thus, we aim to identify relevant words in those datasets and analyze how they can affect model learning. For keyword extraction, we propose an unsupervised hybrid approach which combines the multi-head self-attention of BERT and a reasoning on a word graph. The attention mechanism allows to capture relationships among words in a context, while a language model is learned. Then, the relationships are used to generate a graph from what we identify the most relevant words by using the eigenvector centrality. Experiments were performed by means of two mechanisms. On the one hand, we used an information retrieval system to evaluate the impact of the keywords in recovering offensive tweets from a dataset. On the other hand, we evaluated a keyword-based model for offensive language detection. Results highlight some points to consider when training models with available datasets.

Highly negative dispersion compensating fiber with low third order dispersion

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Md. Ibadul Islam ◽  
Md Saiful Islam
Keyword(s):  
Group Velocity Dispersion ◽  
Chromatic Dispersion ◽  
Third Order ◽  
Crystal Fiber ◽  
Negative Dispersion ◽  
Third Order Dispersion ◽  
Sensing Applications ◽  
Effective Mode Area ◽  
Mode Area ◽  
Order Dispersion

AbstractIn this work, a dispersion compensating photonic crystal fiber (DC-PCF) is proposed in which dispersion, dispersion slope, second order dispersion, third order dispersion, nonlinearity, effective mode area, V parameter are investigated. The suggested structure is very effective for compensating of chromatic dispersion about −951 to −3075.10 ps/(nm.km) over 1340–1640 nm wavelength bandwidth. With perfectly matched layer boundary condition, guiding properties are inspected applying finite element method (FEM). The investigated results conform the opportunity of large negative dispersion and high group velocity dispersion (GVD) of −2367.10 ps/(nm.km) and 3018.55 ps2/km respectively, at 1550 nm operating wavelength. The offered fiber also shows low third order dispersion about −637.88 ps3/km, high nonlinearity of 91.11 W−1 km−1. From overall simulation results, it can be expected that the suggested PCF will be an effective candidate in high bit rate long haul optical communication system as well as sensing applications.

scholarly journals Synchronization in 5G networks: a hybrid Bayesian approach toward clock offset/skew estimation and its impact on localization

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Meysam Goodarzi ◽  
Darko Cvetkovski ◽  
Nebojsa Maletic ◽  
Jesús Gutiérrez ◽  
Eckhard Grass
Keyword(s):  
Bayesian Approach ◽  
Large Scale ◽  
Hybrid Approach ◽  
Position Estimation ◽  
5G Networks ◽  
Clock Skew ◽  
Depth Analysis ◽  
The Impact ◽  
Mean Square Errors ◽  
Clock Offset

AbstractClock synchronization has always been a major challenge when designing wireless networks. This work focuses on tackling the time synchronization problem in 5G networks by adopting a hybrid Bayesian approach for clock offset and skew estimation. Furthermore, we provide an in-depth analysis of the impact of the proposed approach on a synchronization-sensitive service, i.e., localization. Specifically, we expose the substantial benefit of belief propagation (BP) running on factor graphs (FGs) in achieving precise network-wide synchronization. Moreover, we take advantage of Bayesian recursive filtering (BRF) to mitigate the time-stamping error in pairwise synchronization. Finally, we reveal the merit of hybrid synchronization by dividing a large-scale network into local synchronization domains and applying the most suitable synchronization algorithm (BP- or BRF-based) on each domain. The performance of the hybrid approach is then evaluated in terms of the root mean square errors (RMSEs) of the clock offset, clock skew, and the position estimation. According to the simulations, in spite of the simplifications in the hybrid approach, RMSEs of clock offset, clock skew, and position estimation remain below 10 ns, 1 ppm, and 1.5 m, respectively.

scholarly journals Monoclinic and Orthorhombic NaMnO2 for Secondary Batteries: A Comparative Study

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1230
Author(s):  
Jessica Manzi ◽  
Annalisa Paolone ◽  
Oriele Palumbo ◽  
Domenico Corona ◽  
Arianna Massaro ◽  
...  
Keyword(s):  
Structural Parameters ◽  
Reversible Capacity ◽  
Beta Phase ◽  
X Ray Diffraction ◽  
Positive Electrodes ◽  
Detailed Structural Analysis ◽  
Physico Chemical ◽  
Sodium Batteries ◽  
The Impact ◽  
First Time

In this manuscript, we report a detailed physico-chemical comparison between the α- and β-polymorphs of the NaMnO2 compound, a promising material for application in positive electrodes for secondary aprotic sodium batteries. In particular, the structure and vibrational properties, as well as electrochemical performance in sodium batteries, are compared to highlight differences and similarities. We exploit both laboratory techniques (Raman spectroscopy, electrochemical methods) and synchrotron radiation experiments (Fast-Fourier Transform Infrared spectroscopy, and X-ray diffraction). Notably the vibrational spectra of these phases are here reported for the first time in the literature as well as the detailed structural analysis from diffraction data. DFT+U calculations predict both phases to have similar electronic features, with structural parameters consistent with the experimental counterparts. The experimental evidence of antisite defects in the beta-phase between sodium and manganese ions is noticeable. Both polymorphs have been also tested in aprotic batteries by comparing the impact of different liquid electrolytes on the ability to de-intercalated/intercalate sodium ions. Overall, the monoclinic α-NaMnO2 shows larger reversible capacity exceeding 175 mAhg−1 at 10 mAg−1.

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