Wavelength Dimension Research Articles

Improvement of a Terahertz Detector Performance Using the Terajet Effect in a Mesoscale Dielectric Cube: Proof of Concept

A dielectric cube, with dimensions of wavelength, was placed at the length of terajet in front of a terahertz detector. Enhancement of the detector responsivity by 4.3 dB with a decrease of noise equivalent power was experimentally demonstrated under excitation of 0.3 THz (see article number 1900700 by Yahya Moubarak Meziani and co-workers). This opens the way for the development of new THz detectors that could overcome the diffraction limit obstacle.

Determination of an Objective Criterion for the Assessment of the Feasibility of an Instrumented Indentation Test on Rough Surfaces.

The influence of roughness on the results of indentation testing was investigated using a semianalytical model. This model used simulated surfaces that were described using three standard roughness parameters: the root-mean-square deviation Sq, the wavelength (or cut-off of Gaussian high-pass filter), and the fractal dimension. It was shown that Sq had the largest effect on the determination of the macrohardness, while the surface wavelength and fractal dimension had negligible effects at the scale of investigation. The error of determination of the macrohardness rose with the increase of the ratio Sq/hmax where hmax was the maximum indentation depth: Sq/hmax ratios lower than 0.02 were required to obtain a systematic error of the macrohardness lower than 5%, whatever the examined material mechanical properties (in elasticity and plasticity).

Pre-processing visualization of hyperspectral fluorescent data with Spectrally Encoded Enhanced Representations

Hyperspectral fluorescence imaging is gaining popularity for it enables multiplexing of spatio-temporal dynamics across scales for molecules, cells and tissues with multiple fluorescent labels. This is made possible by adding the dimension of wavelength to the dataset. The resulting datasets are high in information density and often require lengthy analyses to separate the overlapping fluorescent spectra. Understanding and visualizing these large multi-dimensional datasets during acquisition and pre-processing can be challenging. Here we present Spectrally Encoded Enhanced Representations (SEER), an approach for improved and computationally efficient simultaneous color visualization of multiple spectral components of hyperspectral fluorescence images. Exploiting the mathematical properties of the phasor method, we transform the wavelength space into information-rich color maps for RGB display visualization. We present multiple biological fluorescent samples and highlight SEER’s enhancement of specific and subtle spectral differences, providing a fast, intuitive and mathematical way to interpret hyperspectral images during collection, pre-processing and analysis.

Gas Sensitivity Amplification of Interdigitated Chemocapacitors Through Etching

In polymer coated planar Inter Digitated Electrodes (IDEs), the gas sensing sensitivity is much lower than the sensitivity of parallel plate capacitors. Here, we introduce a simple patterning step for the modification of the geometry of the dielectric substrate of the planar IDEs, and increase of the contribution of the sensitive layer to the output signal. The proposed methodology is investigated through simulation and verified by experimental data. Polymer coated IDEs with different dimensions of spatial wavelength were studied experimentally upon exposure to analytes of varying polarity. The sensing performance of the fabricated structures compare very well with theoretically estimated values obtained through finite element simulations. The maximum performance gain is also calculated by simulation demonstrating the potential of the technology.

Machine Learning Regression Approach to the Nanophotonic Waveguide Analyses

Machine learning is an application of artificial intelligence that focuses on the development of computer algorithms which learn automatically by extracting patterns from the data provided. Machine learning techniques can be efficiently used for a problem with a large number of parameters to be optimized and also where it is infeasible to develop an algorithm of specific instructions for performing the task. Here, we combine the finite element simulations and machine learning techniques for the prediction of mode effective indices, power confinement, and coupling length of different integrated photonics devices. Initially, we prepare a dataset using COMSOL Multiphysics and then this data is used for training while optimizing various parameters of the machine learning model. Waveguide width, height, operating wavelength, and other device dimensions are varied to record different modal solution parameters. A detailed study has been carried out for a slot waveguide structure to evaluate different machine learning model parameters including number of layers, number of nodes, choice of activation functions, and others. After training, this model is used to predict the outputs for new input device specifications. This method predicts the output for different device parameters faster than direct numerical simulation techniques. Absolute percentage error of less than 5% in predicting an output has been obtained for slot, strip, and directional waveguide coupler designs. This study paves the step towards using machine learning based optimization techniques for integrated silicon photonics devices.

Tight focusing properties of phase modulated azimuthally polarized doughnut Gaussian vortex beam by high NA parabolic mirror

The intensity distribution in the focal region of a high NA parabolic mirror for the incident azimuthally polarized doughnut Gaussian vortex beam (DGVB) transmitted through a multi belt complex phase filter (MBCF) is studied using vector diffraction theory. By properly designing the phase of the incident beam using MBCF and by tuning the beam parameters of a DGVB, it is possible to switch the focal spot with sub wavelength dimension and long focal depth in to multiple focal spots suitable for particle acceleration, atom optical experiments, and near-field scanning optical microscopy.

Spectral Deconvolution for Dimension Reduction and Differentiation of Seagrasses: Case Study of Gulf St. Vincent, South Australia

Seagrasses are a vulnerable and declining coastal habitat, which provide shelter and substrate for aquatic microbiota, invertebrates, and fishes. More accurate mapping of seagrasses is imperative for their sustainability but is hindered by the lack of data on reflectance spectra representing the optical signatures of individual species. Objectives of this study are: (1) To determine distinct characteristics of spectral profiles for sand versus three temperate seagrasses (Posidonia, Amphibolis, and Heterozostera); (2) to evaluate the most efficient derivative analysis method of spectral reflectance profiles for determining benthic types; and to assess the influences of (3) site location and (4) the water column on spectral responses. Results show that 566:689 and 566:600 bandwidth ratios are useful in separating seagrasses from sand and from detritus and algae, respectively; first-derivative reflectance spectra generally is the most efficient method, especially with deconvolution analyses further helping to reveal and isolate 11 key wavelength dimensions; and differences between sites and water column composition, which can include suspended particulate matter, both have no effect on endmembers. These findings helped develop a spectral reflectance library that can be used as an endmember reference for remote sensing, thereby providing continued monitoring, assessment, and management of seagrasses.

Time-resolved plasma spectroscopy of diatomic molecular cyanide

In this work, measurements of cyanide (CN) molecular spectra following laser-induced optical breakdown are communicated. The recorded time-resolved data are Abel inverted to determine the spatial distributions of the maximum CN signals and to evaluate molecular excitation temperatures. The experiments are conducted in a 1:1 CO2:N2 gas mixture contained in a cell kept at atmospheric pressure, and the micro-plasma is generated using 150 mJ, 6 ns Q-switched Nd:YAG laser radiation. The optical emissions from the micro-plasma are dispersed using a 0.64 m spectrometer and are recorded along the wavelength and slit dimensions using an intensified charge-coupled device.

Layered OXC With Intermode Switching Bridge for Optical SDM-WDM Networks

Recently, spatial-division-multiplexing based on weakly coupled multicore or few-mode fibers has been proposed for short-reach switching scenarios, in which spatial mode can be used as an independent switching dimension. Fully connected cross-connections (OXC) converting all spatial modes and wavelengths into one-dimensional switching ports and followed by huge switching array can provide nonblocking switching, but the hardware implementation is very complex and expensive. In this paper, we propose a layered OXC structure consisting of intramode sub-OXCs and intermode switching bridges. Then, a scattered-spectrum-scan intramode-first routing and spectrum allocation (SSS-IMF-RSA) scheme is designed, in which only a few discrete spectrum segments instead of the whole spectrum should be scanned for spectrum allocation. The switching will be performed preferentially for the wavelength dimension because of mature switching capability and less searching time. We show by simulation that the proposed layered OXC with the SSS-IMF-RSA scheme can achieve similar blocking performance to fully connected OXCs with up to 76.1% hardware scale reduction and 93% searching time reduction for network accommodation. The proposed OXC and RSA scheme greatly decrease the requirements for the port number of WSS and enable components reuse to achieve smooth evolution.

Highly directive 3D‐printed dual‐beam waveguide slotted antennas for millimeter‐wave applications

AbstractA highly directive 3D‐printed dual beam waveguide slotted antennas designed at 28 GHz are presented in this work. By having dual‐beam directional pattern, the coverage area can be doubled. The performance of dual‐beam waveguide slotted antennas is investigated with new metal 3D printing technique. The slots are basically designed at half wavelength dimension and distance with symmetrical and asymmetrical offset to form different phase radiations. The longitudinal slotted arrays are implemented on both side of the waveguide broad walls, thus enabling the dual beams on the antenna. The proposed antennas are simulated using computer simulation technology software and fully metal printed using EOS M280 machine. The simulated performance is validated experimentally using network analyzer measurement. The dimensional tolerance and surface roughness are profiled in this work. A good match better than 10 dB is achieved. The antennas are proposed for three‐dimensional beamforming in millimetre wave applications.

Reconfigurable Microwave Photonic Filter Based on Long Period Gratings Inscribed in Multicore Fibers

We propose and experimentally demonstrate a reconfigurable finite impulse response microwave photonic filter (FIR-MPF) based on long period gratings (LPGs) inscribed in multicore fibers. By exploiting two dimensions of optical wavelength and space, intentional inter-core signal switching is realized. For the diversity of optical wavelength, we tune the operation wavelength to change the inter-core power coupling according to the wavelength-dependent characteristic of LPGs. On the other hand, for the diversity of space, we use directional bending of LPGs to achieve switchable spatial channel allocation. Both configurations can implement three different two-tap FIR-MPFs individually. We show a promising solution for reconfigurable radio frequency signal processing in potential with low cost and high efficiency.

Detection of K in soil using time-resolved laser-induced breakdown spectroscopy based on convolutional neural networks

One of the technical bottlenecks of traditional laser-induced breakdown spectroscopy (LIBS) is the difficulty in quantitative detection caused by the matrix effect. To troubleshoot this problem, this paper investigated a combination of time-resolved LIBS and convolutional neural networks (CNNs) to improve K determination in soil. The time-resolved LIBS contained the information of both wavelength and time dimension. The spectra of wavelength dimension showed the characteristic emission lines of elements, and those of time dimension presented the plasma decay trend. The one-dimensional data of LIBS intensity from the emission line at 766.49 nm were extracted and correlated with the K concentration, showing a poor correlation of = 0.0967, which is caused by the matrix effect of heterogeneous soil. For the wavelength dimension, the two-dimensional data of traditional integrated LIBS were extracted and analyzed by an artificial neural network (ANN), showing = 0.6318 and the root mean square error of validation (RMSEV) = 0.6234. For the time dimension, the two-dimensional data of time-decay LIBS were extracted and analyzed by ANN, showing = 0.7366 and RMSEV = 0.7855. These higher determination coefficients reveal that both the non-K emission lines of wavelength dimension and the spectral decay of time dimension could assist in quantitative detection of K. However, due to limited calibration samples, the two-dimensional models presented over-fitting. The three-dimensional data of time-resolved LIBS were analyzed by CNNs, which extracted and integrated the information of both the wavelength and time dimension, showing the = 0.9968 and RMSEV = 0.0785. CNN analysis of time-resolved LIBS is capable of improving the determination of K in soil.

Enhancement of pupil-masked wavelength-scale gas-filled flat acoustic lens based on anomaly apodization effect

In this letter, the improvement in focus by the use of a pupil mask produced in an acoustic mesoscale cuboid particle filled with CO2 is reported. Thereby, the result shows that the pupil mask increases the sound intensity and also increases the resolution (or a reduction of the full width at half maximum, FWHM) in focus compared to the non-masked one. These results are important because they confirm the effect of abnormal amplitude apodization for a one-wavelength dimension acoustic lens and demonstrate that it is possible to improve sound focusing of a cuboid gas-filled lens with one wavelength dimension. This is the smallest size of an acoustic lens ever considered in this type of literature, with side dimensions of the cube equal to one wavelength and a diameter to focus ratio of 2.5, the sound amplification in focus is 5.4 dB at 4125 Hz, with the resolution near to the diffraction limit.

Silicon-based wavelength division multiplexer by exploiting mode conversion in asymmetric directional couplers

We propose a kind of wavelength division multiplexer (WDM) based on asymmetric directional couplers (ADCs). Wavelength signals are multiplexed into a bus waveguide by converting to different modes using the cascaded ADCs. We design the WDMs with conventional and tapered ADCs and analyze the performance in terms of insertion loss, crosstalk, and fabrication tolerance. Experimental results indicate that the WDM with tapered ADCs has both lower insertion loss (less than 1dB) and crosstalk (less than -23dB), and at the same time it has better fabrication tolerance than conventional ADCs. The ADC-based WDMs, which demonstrate good performance of multiplexing wavelengths, own the advantages of simple structure, high flexibility, and scalability. Since different wavelengths perform mode conversion on the same plane, the proposed WDM can be conveniently integrated on-chip with active and passive devices. Our approach combines both wavelength and mode dimensions, which is different from previous schemes, so it is expected to provide an alternative to developing a promising WDM in integrated silicon-based circuits.

Influence of uniaxial deformation on structure of carbon-coated polyurethane surface

Plasma treatment of polymers is the promising technique for improving the quality of biomedical devices, in particular deformable implants. The influence of mechanical deformation on such coating has not been sufficiently studied. The effect of the uniaxial cyclic deformation on the surface structure of carbon nanolayer deposited (by the magnetron sputtering) on soft elastic polyurethane is investigated. The obtained coating is wrinkled. The mechanical load changes the structure of the surface (wavelength, amplitude and fractal dimension of the wrinkles, surface roughness); the cracks appear on the deposited layer. As the strain increases, the number of cracks rises and the strain-induced folds appear on the coating.

Realization and Application of Large-Scale Fast Optical Circuit Switch for Data Center Networking

Applying optical switching to data center networks can greatly expand network bandwidth and reduce electrical power consumption, both of which are needed to meet the explosive traffic increase. The optical switch offers large bandwidth switching capability, and so eliminates the multistage switch network architecture needed with electrical switching. Furthermore, the single stage architecture of the optical switch greatly simplifies operating costs, which include cabling, while substantially reducing the number of transponders needed. Data center networks place very different demands on optical systems than communication networks. Grasping the right direction to proceed is of paramount importance. To realize the full potential of optical switches, such as scalability and cost effectiveness, we analyze the role of large-scale optical circuit switches and discuss the realization technologies that combine the two dimensions of space and wavelength. Our recent advances in large port-count optical switches are presented.

Near-Field Mapping of Optical Fabry-Perot Modes in All-Dielectric Nanoantennas.

Subwavelength optical resonators and scatterers are dramatically expanding the toolset of the optical sciences and photonics engineering. By offering the opportunity to control and shape light waves in nanoscale volumes, recent developments using high-refractive-index dielectric scatterers gave rise to efficient flat-optical components such as lenses, polarizers, phase plates, color routers, and nonlinear elements with a subwavelength thickness. In this work, we take a deeper look into the unique interaction of light with rod-shaped amorphous silicon scatterers by tapping into their resonant modes with a localized subwavelength light source-an aperture scanning near-field probe. Our experimental configuration essentially constitutes a dielectric antenna that is locally driven by the aperture probe. We show how leaky transverse electric and magnetic modes can selectively be excited and form specific near-field distribution depending on wavelength and antenna dimensions. The probe's transmittance is furthermore enhanced upon coupling to the Fabry-Perot cavity modes, revealing all-dielectric nanorods as efficient transmitter antennas for the radiation of subwavelength emitters, in addition to constituting an elementary building block for all-dielectric metasurfaces and flat optics.

Laboratory studies of ultrasonic wave response of fractures with different lengths: Anisotropy characteristics and coda analysis

Ultrasonic wave propagation in a synthetic medium with different scale fractures is investigated through the physics modeling research. The experiment model consisting of two layers, the first layer is divided into four fractured blocks with a constant fracture density but different dimension and a block without fractures as the reference region. The velocity and reflected amplitude of wave derived from the wide azimuth data processing are anisotropic due to the fractured layer. Coda wave characteristics versus offset and azimuth are obviously different for varying fracture scales. The ratio of wavelength and fracture dimension is an important parameter in the wave-fracture interaction based on the multiple scattering theory. When the wavelength of the incident wave is close to the fracture length, the scattering is dominant in the shot records and the waves are slowed and attenuated largely for the reflections from the bottoms of fractured layer and base model. The physical modeling results demonstrate that it is possible to extract fracture dimension and orientation information by analyzing code and primary waves from the reflection data.

Versatile Spectral and Lifetime Multiplexing Nanoplatform with Excitation Orthogonalized Upconversion Luminescence.

Optical encoding together with color multiplexing benefits on-site detection, and enriching the components with narrow emissions from lanthanide could greatly increase the coding density. Here, we show a typical example to combine emission color and lifetime that are simultaneously integrated in a single lanthanide nanoparticle. With the multicompartment core/shell structure, the nanoparticles can activate different emitting pathways under varied excitation. This enables the nanoparticles to generate versatile excitation orthogonalized upconversion luminescence in both emission colors and lifetimes. As a typical example, green emission of Er3+ and blue emission of Tm3+ can be triggered with 808 and 980 nm lasers, respectively. Moreover, with incorporation of Tb3+, not only is emission from Tb3+ introduced but also the lifetime difference of 0.13 ms (Er3+) and 3.6 ms (Tb3+) is yielded for the green emission, respectively. Multiplexed fingerprint imaging and time-gated luminescence imaging were achieved in wavelength and lifetime dimensions. The spectral and lifetime encoding ability from lanthanide luminescence greatly broadens the scope of luminescent materials for optical multiplexing studies.

Enhanced Tissue Ablation Efficiency with a Mid-Infrared Nonlinear Frequency Conversion Laser System and Tissue Interaction Monitoring Using Optical Coherence Tomography.

We report development of optical parametric oscillator (OPO)-based mid-infrared laser system that utilizes a periodically poled nonlinear crystal pumped by a near-infrared (NIR) laser. We obtained a mid-infrared average output of 8 W at an injection current of 20 A from a quasi-phase-matched OPO using an external cavity configuration. Laser tissue ablation efficiency is substantially affected by several parameters, including an optical fluence rate, wavelength of the laser source, and the optical properties of target tissue. Dimensions of wavelength and radiant exposure dependent tissue ablation are quantified using Fourier domain optical coherence tomography and the ablation efficiency was compared to a non-converted NIR laser system.