scholarly journals Fabrication of Tapered Circular Depressed-Cladding Waveguides in Nd:YAG Crystal by Femtosecond-Laser Direct Inscription

Micromachines ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 10 ◽  
Author(s):  
Carolina Romero ◽  
Javier García Ajates ◽  
Feng Chen ◽  
Javier R. Vázquez de Aldana
Keyword(s):  
Near Infrared ◽  
Femtosecond Lasers ◽  
Three Dimensional ◽  
Photonic Devices ◽  
Circular Section ◽  
Crystalline Materials ◽  
Frequency Converters ◽  
Transparent Substrate ◽  
Modal Behavior ◽  
Nd:Yag Crystal

Crystalline materials are excellent substrates for the integration of compact photonic devices benefiting from the unique optical properties of these materials. The technique of direct inscription with femtosecond lasers, as an advantage over other techniques, has opened the door to the fabrication of true three-dimensional (3D) photonic devices in almost any transparent substrate. Depressed-cladding waveguides have been demonstrated to be an excellent and versatile platform for the integration of 3D photonic circuits in crystals. Here, we present the technique that we have developed to inscribe tapered depressed-cladding waveguides with a circular section for the control of the modal behavior. As a proof of concept, we have applied the technique to fabricate structures in Nd:YAG crystal that efficiently change the modal behavior from highly multimodal to monomodal, in the visible and near infrared, with reduction factors in the waveguide radius of up to 4:1. Our results are interesting for different devices such as waveguide lasers, frequency converters or connectors between external devices with different core sizes.

Prototyping of three-dimensional photonic crystal structures using electron-beam lithography

2004 ◽  
Vol 846 ◽  
Author(s):  
G. Subramania ◽  
J. M. Rivera
Keyword(s):  
Electron Beam ◽  
Photonic Crystal ◽  
Electron Beam Lithography ◽  
Near Infrared ◽  
Photonic Band Gap ◽  
Three Dimensional ◽  
Photonic Devices ◽  
Layer By Layer ◽  
Photonic Band Gap Structure ◽  
Band Gap Structure

ABSTRACTWe demonstrate the fabrication of a three-dimensional woodpile photonic crystal in the near-infrared regime using a layer-by-layer approach involving electron-beam lithography and spin-on-glass planarization. Using this approach we have shown that we can make structures with lattice spacings as small as 550 nm with silicon as well as gold thus allowing for fabrication of photonic crystals with omnidirectional gap in the visible and near-IR. As a proof of concept we performed optical reflectivity and transmission measurements on a silicon structure which reveal peaks and valleys expected for a photonic band gap structure. The approach described here can be scaled down to smaller lattice constants (down to ∼400 nm) and can also be used with a variety of materials (dielectric and metallic) thus enabling rapid prototyping full three-dimensional photonic bandgap based photonic devices in the visible.

Urban energetics applications and Geomatic technologies in a Smart City perspective

2015 ◽  
Vol 6 (1) ◽  
pp. 19-29 ◽  
Author(s):  
G. Bitelli ◽  
P. Conte ◽  
T. Csoknyai ◽  
E. Mandanici
Keyword(s):  
Smart City ◽  
Laser Scanning ◽  
Near Infrared ◽  
Three Dimensional ◽  
Energy Sector ◽  
Primary Objective ◽  
Airborne Lidar ◽  
City Management ◽  
Urban Context ◽  
Research Areas

The management of an urban context in a Smart City perspective requires the development of innovative projects, with new applications in multidisciplinary research areas. They can be related to many aspects of city life and urban management: fuel consumption monitoring, energy efficiency issues, environment, social organization, traffic, urban transformations, etc. Geomatics, the modern discipline of gathering, storing, processing, and delivering digital spatially referenced information, can play a fundamental role in many of these areas, providing new efficient and productive methods for a precise mapping of different phenomena by traditional cartographic representation or by new methods of data visualization and manipulation (e.g. three-dimensional modelling, data fusion, etc.). The technologies involved are based on airborne or satellite remote sensing (in visible, near infrared, thermal bands), laser scanning, digital photogrammetry, satellite positioning and, first of all, appropriate sensor integration (online or offline). The aim of this work is to present and analyse some new opportunities offered by Geomatics technologies for a Smart City management, with a specific interest towards the energy sector related to buildings. Reducing consumption and CO2 emissions is a primary objective to be pursued for a sustainable development and, in this direction, an accurate knowledge of energy consumptions and waste for heating of single houses, blocks or districts is needed. A synoptic information regarding a city or a portion of a city can be acquired through sensors on board of airplanes or satellite platforms, operating in the thermal band. A problem to be investigated at the scale A problem to be investigated at the scale of the whole urban context is the Urban Heat Island (UHI), a phenomenon known and studied in the last decades. UHI is related not only to sensible heat released by anthropic activities, but also to land use variations and evapotranspiration reduction. The availability of thermal satellite sensors is fundamental to carry out multi-temporal studies in order to evaluate the dynamic behaviour of the UHI for a city. Working with a greater detail, districts or single buildings can be analysed by specifically designed airborne surveys. The activity has been recently carried out in the EnergyCity project, developed in the framework of the Central Europe programme established by UE. As demonstrated by the project, such data can be successfully integrated in a GIS storing all relevant data about buildings and energy supply, in order to create a powerful geospatial database for a Decision Support System assisting to reduce energy losses and CO2 emissions. Today, aerial thermal mapping could be furthermore integrated by terrestrial 3D surveys realized with Mobile Mapping Systems through multisensor platforms comprising thermal camera/s, laser scanning, GPS, inertial systems, etc. In this way the product can be a true 3D thermal model with good geometric properties, enlarging the possibilities in respect to conventional qualitative 2D images with simple colour palettes. Finally, some applications in the energy sector could benefit from the availability of a true 3D City Model, where the buildings are carefully described through three-dimensional elements. The processing of airborne LiDAR datasets for automated and semi-automated extraction of 3D buildings can provide such new generation of 3D city models.

scholarly journals Electromechanically reconfigurable optical nano-kirigami

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Shanshan Chen ◽  
Zhiguang Liu ◽  
Huifeng Du ◽  
Chengchun Tang ◽  
Chang-Yin Ji ◽  
...  
Keyword(s):  
Near Infrared ◽  
Large Range ◽  
Three Dimensional ◽  
High Contrast ◽  
Si Substrate ◽  
High Modulation ◽  
Gold Nanostructure ◽  
Infrared Wavelengths ◽  
On Chip ◽  
Nano Electromechanical System

AbstractKirigami, with facile and automated fashion of three-dimensional (3D) transformations, offers an unconventional approach for realizing cutting-edge optical nano-electromechanical systems. Here, we demonstrate an on-chip and electromechanically reconfigurable nano-kirigami with optical functionalities. The nano-electromechanical system is built on an Au/SiO2/Si substrate and operated via attractive electrostatic forces between the top gold nanostructure and bottom silicon substrate. Large-range nano-kirigami like 3D deformations are clearly observed and reversibly engineered, with scalable pitch size down to 0.975 μm. Broadband nonresonant and narrowband resonant optical reconfigurations are achieved at visible and near-infrared wavelengths, respectively, with a high modulation contrast up to 494%. On-chip modulation of optical helicity is further demonstrated in submicron nano-kirigami at near-infrared wavelengths. Such small-size and high-contrast reconfigurable optical nano-kirigami provides advanced methodologies and platforms for versatile on-chip manipulation of light at nanoscale.

scholarly journals Hydrothermal Synthesis and Structural Investigation of a Crystalline Uranyl Borosilicate

Inorganics ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 25
Author(s):  
Kristen A. Pace ◽  
Vladislav V. Klepov ◽  
Mark D. Smith ◽  
Travis Williams ◽  
Gregory Morrison ◽  
...  
Keyword(s):  
Synthesis Method ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Exploratory Research ◽  
The Novel ◽  
Orthorhombic Space Group ◽  
Crystalline Materials ◽  
Waste Remediation ◽  
And Storage ◽  
X Ray Absorption

The relevance of multidimensional and porous crystalline materials to nuclear waste remediation and storage applications has motivated exploratory research focused on materials discovery of compounds, such as actinide mixed-oxoanion phases, which exhibit rich structural chemistry. The novel phase K1.8Na1.2[(UO2)BSi4O12] has been synthesized using hydrothermal methods, representing the first example of a uranyl borosilicate. The three-dimensional structure crystallizes in the orthorhombic space group Cmce with lattice parameters a = 15.5471(19) Å, b = 14.3403(17) Å, c = 11.7315(15) Å, and V = 2615.5(6) Å3, and is composed of UO6 octahedra linked by [BSi4O12]5− chains to form a [(UO2)BSi4O12]3− framework. The synthesis method, structure, results of Raman, IR, and X-ray absorption spectroscopy, and thermal stability are discussed.

Effect of color converters on the performance of solar or light-emitting diode pumped solid-state lasers

2020 ◽  
Vol 22 (5) ◽  
pp. 287-290
Author(s):  
A.A. Sherniyozov ◽  
Sh.D. Payziyev ◽  
G.A. Khalikov ◽  
Kh.F. Zikrillayev ◽  
S.A. Bakhramov ◽  
...  
Keyword(s):  
Luminescence Intensity ◽  
Light Emitting Diode ◽  
Potential Candidate ◽  
Solid State Lasers ◽  
Light Emitting ◽  
Frequency Converters ◽  
External Frequency ◽  
Diode Pumped ◽  
Color Converter ◽  
Nd:Yag Crystal

The effect of using external frequency converters on the luminescence intensity of an Nd:YAG crystal is studied. The crystal is illuminated by light-emitting diode (LED) with and without Y3Al5O12:Ce3+ material as an external converter. Obtained experimental results show that the luminescence intensity of Nd:YAG crystal increased by 1.5 times when Nd:YAG crystal is illuminated by LED together with color converter based on Y3Al5O12:Ce3+ demonstrating that external frequency converters can be a potential candidate for creating more efficient solar or LED pumped lasers.

scholarly journals Deep learning classifiers for near infrared spectral imaging: a tutorial

2020 ◽  
Author(s):  
Jun-Li Xu ◽  
Cecilia Riccioli ◽  
Ana Herrero-Langreo ◽  
Aoife Gowen
Keyword(s):  
Deep Learning ◽  
Visual Recognition ◽  
Near Infrared ◽  
Three Dimensional ◽  
Spectral Imaging ◽  
Learning Approaches ◽  
Imaging Data ◽  
Spectral Image ◽  
Background Removal ◽  
Wide Range

Deep learning (DL) has recently achieved considerable successes in a wide range of applications, such as speech recognition, machine translation and visual recognition. This tutorial provides guidelines and useful strategies to apply DL techniques to address pixel-wise classification of spectral images. A one-dimensional convolutional neural network (1-D CNN) is used to extract features from the spectral domain, which are subsequently used for classification. In contrast to conventional classification methods for spectral images that examine primarily the spectral context, a three-dimensional (3-D) CNN is applied to simultaneously extract spatial and spectral features to enhance classificationaccuracy. This tutorial paper explains, in a stepwise manner, how to develop 1-D CNN and 3-D CNN models to discriminate spectral imaging data in a food authenticity context. The example image data provided consists of three varieties of puffed cereals imaged in the NIR range (943–1643 nm). The tutorial is presented in the MATLAB environment and scripts and dataset used are provided. Starting from spectral image pre-processing (background removal and spectral pre-treatment), the typical steps encountered in development of CNN models are presented. The example dataset provided demonstrates that deep learning approaches can increase classification accuracy compared to conventional approaches, increasing the accuracy of the model tested on an independent image from 92.33 % using partial least squares-discriminant analysis to 99.4 % using 3-CNN model at pixel level. The paper concludes with a discussion on the challenges and suggestions in the application of DL techniques for spectral image classification.

Nondegenerate and degenerate two-photon absorption in cuprous oxide thin film

2019 ◽  
Vol 28 (02) ◽  
pp. 1950015 ◽  
Author(s):  
Huijun Liang ◽  
Qunchao Ma ◽  
Jian Liu ◽  
Xinwei Shi ◽  
Gongjin Yang ◽  
...  
Keyword(s):  
Thin Film ◽  
Cuprous Oxide ◽  
Near Infrared ◽  
Rf Magnetron Sputtering ◽  
Photonic Devices ◽  
Photon Absorption ◽  
Oxide Thin Film ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Nir Absorption

A cuprous oxide (Cu2O) thin film was prepared by radio-frequency (RF) magnetron sputtering. The crystal structure, linear transmission spectrum and film thickness were characterized by X-ray diffraction (XRD), ultraviolet–visible–near infrared (UV–Vis–NIR) absorption spectroscopy and ellipsometry. By performing the pump-probe and [Formula: see text]-scan technique, respectively, nondegenerate and degenerate two-photon absorption (D-TPA) coefficients of the Cu2O thin film at several different excitation wavelengths were experimentally determined. The nondegenerate two-photon absorption (ND-TPA) coefficient always exhibits larger magnitude than the corresponding D-TPA coefficient. In particular, the ND-TPA coefficient shows a maximum value of [Formula: see text][Formula: see text]cm/GW. This study indicates that the cuprous oxide could be a potential material for ultrafast nonlinear photonic devices based on two-photon absorption due to its large ND-TPA coefficient.

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