Power Confinement Research Articles

Numerical optimization of anti resonant hollow core fiber for high sensitivity methane detection

This study presents an innovative methane gas sensor design based on anti-resonant hollow-core fiber (AR-HCF) technology, optimized for high-precision detection at 3.3. Our numerical analysis explores the geometric optimization of the AR-HCF’s structural parameters, incorporating real-world component specifications. The proposed design features a 65 diameter hollow core surrounded by seven silica rings. We achieved significant improvements in confinement loss and optical power distribution through progressive structural modifications. The optimized structure demonstrated a confinement loss of and over 95% optical power confinement in the hollow core. Our model predicts a relative sensitivity of , a response time of 5.4 s, and a theoretical detection threshold of 2.24 ppm. The limit of detection (LoD) was estimated to be 3.8 ppbv, and the normalized noise equivalent absorption (NNEA) coefficient was . The sensor response exhibited excellent linearity over its operating range, with an R2 value of 0.9917 in the critical concentration range. These findings highlight the potential of our AR-HCF-based methane sensor design for real-time gas monitoring applications.

INVESTIGATION OF TUBERCULOSIS SENSING USING GRAPHENE COATED METAMATERIAL FIBER

Abstract Detection of tuberculosis (TB) is being showed a greater interest since it affects the
vital human organ (lungs). In this paper, a biosensor based on optical fiber sensing for
detecting TB is proposed. Here, a hollow core fiber protected with a graphene coated
metamaterial (MM) cladding is numerically investigated in the visible region using finite
element method (FEM). The analyte under test (mycobacterium TB affected haemoglobin) is
filled in the core and the change in refractive index is obtained to calculate the sensitivity.
Further, the proposed fiber is optimized by varying graphene thickness and concentration of
MM and investigated in terms of confinement loss, effective area, power confined to the core
and relative sensitivity. The proposed fiber reports an average relative sensitivity of 92.8%
depicting a power confinement of upto 97.7% and numerical aperture of 0.24. Performance
comparison with other designs is carried out in order to project the efficacy of the proposed
sensor. The obtained sensitivity enables the proposed sensor to be a suitable design in
detection of TB and can be employed in medical diagnosis.

Design of On‐Chip Multi‐Slot Chalcogenide Waveguide for Mid‐Infrared Methane Sensing

ABSTRACTA chalcogenide (ChG) multi‐slot waveguide gas sensor with ChG as the core layer and silicon dioxide (SiO2) as the under‐cladding layer is proposed. Multi‐slot waveguide can be used in the mid‐infrared gas measurement. The optimized power confinement factor (PCF) of the ChG multi‐slot waveguide can be up to 41.3%, which is ∼20% higher than that of the optimized single‐slot waveguide. At the absorption line located at 3.291 μm for methane (CH4) measurement, the limits of detection (LoD) of single‐slot, double‐slot, triple‐slot, quadruple‐slot waveguide sensors are determined to be 68.9, 57.4, 52, 48.6 parts per million (ppm), respectively. Compared with other waveguide sensors in the mid‐infrared, the PCF of the proposed multi‐slot ChG/SiO2 waveguide sensor is enhanced by five times, which has the potential for highly sensitive gas sensing.

Confining Conversion Chemistry in Intercalation Host for Aqueous Batteries

AbstractConversion‐type anode materials with high theoretical capacities play a pivotal role in developing future aqueous rechargeable batteries (ARBs). However, their sustainable applications have long been impeded by the poor cycling stability and sluggish redox kinetics. Here we show that confining conversion chemistry in intercalation host could overcome the above challenges. Using sodium titanates as a model intercalation host, an integrated layered anode material of iron oxide hydroxide‐pillared titanate (FeNTO) is demonstrated. The conversion reaction is spatially and kinetically confined within sub‐nano interlayer, enabling superlow redox polarization (ca. 4–6 times reduced), ultralong lifespan (up to 8700 cycles) and excellent rate performance. Notably, the charge compensation of interlayer via universal cation intercalation into host endows FeNTO with the capability of operating well in a broad range of aqueous electrolytes (Li+, Na+, K+, Mg2+, Ca2+, etc.). We further demonstrate the large‐scale synthesis of FeNTO thin film and powder, and rational design of quasi‐solid‐state high‐voltage ARB pouch cells powering wearable electronics against extreme mechanical abuse. This work demonstrates a powerful confinement means to access disruptive electrode materials for next‐generation energy devices.

Confining Conversion Chemistry in Intercalation Host for Aqueous Batteries.

Conversion-type anode materials with high theoretical capacities play a pivotal role in developing future aqueous rechargeable batteries (ARBs). However, their sustainable applications have long been impeded by the poor cycling stability and sluggish redox kinetics. Here we show that confining conversion chemistry in intercalation host could overcome the above challenges. Using sodium titanates as a model intercalation host, an integrated layered anode material of iron oxide hydroxide-pillared titanate (FeNTO) is demonstrated. The conversion reaction is spatially and kinetically confined within sub-nano interlayer, enabling superlow redox polarization (ca. 4-6 times reduced), ultralong lifespan (up to 8700 cycles) and excellent rate performance. Notably, the charge compensation of interlayer via universal cation intercalation into host endows FeNTO with the capability of operating well in a broad range of aqueous electrolytes (Li+, Na+, K+, Mg2+, Ca2+, etc.). We further demonstrate the large-scale synthesis of FeNTO thin film and powder, and rational design of quasi-solid-state high-voltage ARB pouch cells powering wearable electronics against extreme mechanical abuse. This work demonstrates a powerful confinement means to access disruptive electrode materials for next-generation energy devices.

Optical absorption properties in multi-layer InGaN/GaN core-shell quantum dots: The influences of ternary mixed crystal effect and hydrogen-like impurity

Based on the effective mass approximation and the compact density matrix theory, the electronic states and optical absorption properties of intersubband transitions between the conduction-band energy levels in zinc blende InGaN/GaN/InGaN/GaN core-shell quantum dots (CSQDs) are investigated by using the finite difference method. The effects of hydrogen-like impurity and In component on the wave functions, transition energies, and optical absorption properties are discussed in detail. The results show that hydrogen-like impurity can cause the peak positions of optical absorption coefficients (OACs) and refractive index changes (RICs) to move to high energy area, and the peak values of OACs rise. Increasing In component of InGaN crystal in the core region of a CSQD has the same effect. But an opposite tendency will be found when increasing In component in the shell-well of a CSQD, i.e. optical absorption peaks move to low energy area and their values decrease. Comparing to the shell-well, the core region has more powerful confinement effect on electrons. So the better absorption properties are more likely to be obtained for this type of multi-layer InGaN/GaN CSQDs when In component in the core is larger than that in the shell-well.

What controls river widening? Comparing large and extreme flood events

AbstractExtreme (i.e., centennial‐scale) floods are by definition rare and can therefore be difficult to study. As a result, case studies of response to extreme floods can provide unique insights. On 15 November 2021, the Nicola River in British Columbia, Canada, experienced a 200‐year flood that increased the average width of the Nicola River by more than 50% (35 m), leaving the only highway in the region impassable for nearly 12 months. This research assesses the spatial variability of erosion along a 71‐km‐long segment of the Nicola River during a period with a large flood (2015–2018) and a second period containing the extreme flood in 2021 (2018–2021). We use a random forest statistical analysis to explore the most important valley and channel characteristics affecting relative widening during both periods. Unit stream power, gradient and valley confinement were the primary determinants of erosion during the extreme flood, whereas vegetation cover, channel pattern and surficial material were less important. Erosion during the large flood event was not related to these variables, with channel pattern providing a better indication of widening potential. As the Nicola River is flanked by erodible glacial deposits, this work provides important insight into river response in the paraglacial environments that are common throughout much of Canada and the northern United States, as well as Europe and Asia, but less intensely studied. In these settings, the geomorphic response to large floods may not be representative of the potential erosion (and infrastructure impacts) that can occur during extreme events, which destabilize glacial terraces in confined reaches. Historical observations should therefore be used with caution in paraglacial settings as extreme events may not be captured in available data, creating a perception of stability in confined reaches that may have the potential to erode dramatically during extreme events.

Enhanced Green Light Emission from a Silicon-Based Metal-Encapsulated Nanoplasmonic Waveguide.

Integrated silicon plasmonic circuitry is becoming integral for communications and data processing. One key challenge in implementing such optical networks is the realization of optical sources on silicon platforms, due to silicon's indirect bandgap. Here, we present a silicon-based metal-encapsulated nanoplasmonic waveguide geometry that can mitigate this issue and efficiently generate light via third-harmonic generation (THG). Our waveguides are ideal for such applications, having strong power confinement and field enhancement, and an effective use of the nonlinear core area. This unique device was fabricated, and experimental results show efficient THG conversion efficiencies of η = 4.9 × 10-4, within a core footprint of only 0.24 μm2. Notably, this is the highest absolute silicon-based THG conversion efficiency presented to date. Furthermore, the nonlinear emission is not constrained by phase matching. These waveguides are envisioned to have crucial applications in signal generation within integrated nanoplasmonic circuits.

Full-radius integrated modelling of ASDEX Upgrade L-modes including impurity transport and radiation

An integrated framework that demonstrates multi-species, multi-channel modelling capabilities for the prediction of impurity density profiles and their feedback on the main plasma through radiative cooling and fuel dilution is presented. It combines all presently known theoretical elements in the local description of quasilinear turbulent and neoclassical impurity transport, using the models TGLF-SAT2 and FACIT. These are coupled to the STRAHL code for impurity sources and radiation inside the ASTRA transport solver. The workflow is shown to reproduce experimental results in full-radius L-mode modelling. In particular, a set of ASDEX Upgrade L-modes with differing heating power mixtures and plasma currents are simulated, including boron (B) and tungsten (W) as intrinsic impurities. The increase of predicted confinement with higher current and the reduction of core W peaking with higher central wave heating are demonstrated. Furthermore, a highly radiative L-mode scenario featuring an X-point radiator (XPR) with two intrinsic (B, W) and one seeded argon (Ar) species is simulated, and its measured radiated power and high confinement are recovered by the modelling. The stabilizing effect of impurities on turbulence is analysed and a simple model for the peripheral X-point radiation is introduced. A preliminary full-radius simulation of an H-mode phase of this same discharge, leveraging recent work on the role of the E×B shearing at the edge, shows promising results.

Detection of different drinkable milk using photonic crystal fibre biosensor in IR regime

A simplified PCF sensor has been designed to detect the different drinkable milk that includes camel, cow and buffalo milk, and can also assess its quality. The sensor features a singular circular core design and two layers octagonal cladding air holes that was analysed using the Finite Element Method technique in COMSOL Multiphysics software and determine the sensing and optical performance parameters: power fraction, relative sensitivity, confinement loss, effective area, numerical aperture, V-Parameter, spot size, and beam divergence. At the optimum wavelength of 6.0 μm, the relative sensitivities are 96.58%, 96.78%, and 96.84%, and confinement losses of 3.51 × 10−8 dB/m, 1.47 × 10−8 dB m−1, and 8.59 × 10−9 dB/m, for camel, cow, and buffalo milk, respectively. The efficacy of the proposed PCF structure for sensing applications in the dairy industry in distinguishing between different types of milk is evidenced by these findings. Moreover, the results of confinement loss and chromatic dispersion suggest potential applications of this design in optical communication.

WMS-based near-infrared on-chip acetylene sensor using polymeric SU8 Archimedean spiral waveguide with Euler S-bend

SU8 is a cost-effective polymer material that is highly suitable for large-scale fabrication of waveguides. However, it has not been employed for on-chip gas measurement utilizing infrared absorption spectroscopy. In this study, we propose a near-infrared on-chip acetylene (C2H2) sensor using SU8 polymer spiral waveguides for the first time to our knowledge. The performance of the sensor based on wavelength modulation spectroscopy (WMS) was experimentally validated. By incorporating the proposed Euler-S bend and Archimedean spiral SU8 waveguide, we achieved a reduction in the sensor's size by over fifty percent. Leveraging the WMS technique, we evaluated the C2H2 sensing performance at 1532.83 nm for SU8 waveguides of lengths 7.4 cm and 13 cm. The limit of detection (LoD) values were 2197.1 ppm (parts per million) and 425.5 ppm, respectively, with an averaging time of 0.2 s. Furthermore, the experimentally obtained optical power confinement factor (PCF) closely approximated the simulated value, with a value of 0.0172 compared to the simulated value of 0.016. The waveguide loss is measured to be 3 dB/cm. The rise time and fall time were approximately 2.05 s and 3.27 s, respectively. This study concludes that the SU8 waveguide exhibits significant potential for high-performance on-chip gas sensing in the near-infrared wavelength range.

Optogeometric and waveguiding properties of multimode ZnO planar waveguide sprayed thin films

ZnO thin films with different thicknesses (T1=230.0, T2=450.0, T3=634.0, T4=926.9 and T5=1153.4nm) were deposited by spray pyrolysis on ordinary glass. All of the films had wurtzite crystal structure. The texture coefficient of the (002) plan decreased from 2.74 to 1.64 while that of the (103) increased from 0.65 to 1.23 over the thickness. Flaky shaped grains were observed in the SEM images with a tendency to get larger and hexagonal in shape. The surface evolution was verified by AFM microscopy. The ordinary and extraordinary refractive indices increased with thickness from 1.9344 and 1.9365 to 1.9768 and 1.9830 respectively. The mode order had a significant impact on the confinement of the electric field in the TE mode, therefore the power confinement factor increased by 16.58% with respect to thickness, reaching over 99% whilst it was reduced by 16.39% when the mode order increased from 0 to 4 in T5.

Numerical investigation of a Ge1-xSnx-on-AlN waveguide and its sensing mechanism for the detection of trace gases in the mid-infrared regime

This work reports the integration of a Ge1−xSn x -on-AlN optical waveguide (WG) on SiO2 substrate to facilitate mid-infrared (MIR) trace gas detection. Here, the proposed structure makes use of Ge1−xSn x in the core of the WG and the AlN cladding; this enables the effective guidance and confinement of a broad spectrum of MIR light waves within the GeSn WG. The gas detection mechanism of the device is based on the evanescent wave field component of a guided mode to examine particular molecular absorption/trace gas characteristics of the upper cladding environment. The designed WGs exhibit high power confinement (∼90%) and low propagation loss of 0.61–1.18 dB/cm at λ=4.3−4.74µm with x=6% in the Ge1−xSn x core. We also discuss the capability of the proposed WG to detect trace gases such as CO, CO2, and N2O. The results show that the minimum detectable concentrations (Cmin) of these gases are ∼0.42, 0.12, and 0.16 ppm, respectively, for x=6%. These encouraging results enable a new sensor platform for GeSn-based MIR trace/atmospheric gas detection.

AlGaN-based laser diodes with reduced Al composition in quantum barriers in the deep ultraviolet region

Subject of study. In AlGaN-based deep ultraviolet laser diodes, the quantum well affects the performance in the active region. Moreover, the composition of aluminum in quantum barriers in the quantum well matters to the performance of AlGaN-based deep ultraviolet laser diodes. It might be observed effectively by looking at performance indicators like the emitted power and optical confinement factor (band diagram, carrier concentration, and stimulated recombination). Method. Two deep ultraviolet laser diode devices with a nominated wavelength of 267.5 nm are simulated and compared in this paper using the Crosslight program LASTIP. The proposed deep ultraviolet laser diode device B with a reduced Al composition in the quantum barrier is used in the active region as opposed to the reference deep ultraviolet laser diode device A. Main results. This led to an improvement in emitted output power of 0.109 W with a reduced injection current of 0.02 A and an improvement in the optical confinement factor of 19%. Practical significance. The structure of the reference device is inspired by the experimental structure. The results of the proposed device are calculated and are evaluated based on parameters such as the improved conduction band barrier height, reduced valence band barrier height, and improved stimulated recombination rate. It outperforms the deep ultraviolet laser diode for the reference device.

Numerical analysis of a strip-loaded silicon rich nitride-thin film lithium niobate hybrid waveguides

Hybrid integration of silicon rich nitride and lithium niobate on insulator (SRN-LNOI) is an emerging material platform for photonic integrated circuits (PIC). In this paper, we present a systematic numerical investigation of the mode properties of a strip-loaded SRN-LNOI hybrid waveguide at 1550 nm wavelength using the full-vectorial finite difference method. Considering the anisotropic nature of the lithium niobate (LN) crystal, the effective refractive indices of the transverse electric and transverse magnetic modes of strip-loaded SRN-LN hybrid waveguides were analyzed. The single-mode condition, zero-birefringence, effective mode area, and power distribution in terms of the geometrical parameters of the strip-loaded SRN-LN hybrid waveguide are discussed in detail. Furthermore, the optical power transmission in both straight and bent waveguides, as well as the different characteristics of the optical power confinement of the fundamental modes in the SRN and LN layers were analyzed. This study provides useful information for designing high-performance photonic devices on a hybrid SRN-LNOI platform for future PIC applications.

Silicon Waveguide Sensors for Carbon Dioxide Gas Sensing in the Mid-Infrared Region

Two optical waveguide sensors based on SOS (silicon-on-sapphire) for detecting CO2 are theoretically proposed. The operational wavelength is 4.23 μm, which is the maximum absorption line of CO2. The power confinement factor (η) value is over 40% and 50%, the propagation loss is 0.98 dB/cm and 2.99 dB/cm, respectively, in the slot waveguide and SWGS (subwavelength grating slot) waveguide. An inverted tapered structure is used for the transition from strip waveguide to slot waveguide and constitutes the sensing absorption region, with the coupling efficiency that can reach more than 90%. When the optimal absorption length of the slot waveguide and SWGS waveguide is 1.02 cm and 0.33 cm, respectively, the maximum sensitivity can reach 6.66 × 10−5 (ppm−1) and 2.60 × 10−5 (ppm−1). Furthermore, taking the slot waveguide as an example, spiral and meander structures enable the long-distance sensing path to integrate into a small area.

Retracted: The Use of Deep Learning Model for Effect Analysis of Conventional Friction Power Confinement.

[This retracts the article DOI: 10.1155/2022/8733919.].

Absorption efficiency of the second harmonic ECRH waves and comparative plasma transport simulation in the TJ-II stellarator and T-10 tokamak

The concept of equivalent tokamak and stellarator discharges with the same electron and ion temperatures and with full absorption of the injected ECRH power was introduced in Dnestrovskij et al (2021 Plasma Phys. Control. Fusion 63 055012). In the present paper, the concept of the discharges equivalence is extended to the case of partial ECRH power absorption. The conditions of discharges equivalence for this case are formulated. It is shown that in equivalent discharges not only the electron temperatures, but also the absorbed powers are the same. Examples of equivalent experimental discharges of the TJ-II stellarator and simulated discharges of the T-10 tokamak with partial ECRH power absorption are studied. The absorbed ECRH power and energy confinement time are found for TJ-II low-density shots heated with ECRH only.

The relationship between channel width changes with confinement index and flood power of an extreme flood (Case study: Ilam Dam)

Extreme floods are able to execute river geomorphological variations with a wide and substantial geological changes. Former studies of extreme floods have reported a reach of geomorphic replies from negligible change to catastrophic channel change. This article provides an evaluation of the geomorphic effects of a scarce, great value event that occurred in the Ilam Dam upstearim, on 29 October 2015. Variations in geomorphic replies among reaches are examined in the context of changes in flood power, channel competence and lateral confinement index by the use of field survey and Satellite Images (IRS). In this research which is focused on the plan of spatial units, channel width variations and calculation of peak discharges were used to estimate cross-sectional stream power and unit stream power. The analysis was performed for the widening (width ratio) at reach scale. The total data set includes 38 reaches. Because of the 2015 flood, the largest value of widening was 29 m (Reach 13) and it demonstrated a 100% change in the channel width. Flood power peak was calculated 10631 W m−2 along the rather confined reaches (Reach 31) and was much lower along the unconfined reaches. The tendency of high stream power values, and resultant high erosion rates, within the confined and partly confined reaches is a subordinate of the higher energy slope of the steeper.

Geometric optics analysis of inverted graded index fibers

We derive a general solution based on geometric optics that describes the light propagation properties in multimode optical fibers with inverted refractive index profiles. Using this general solution, we classify rays according to their propagation properties and calculate the analytical expressions of the ray trajectories inside these fibers under different launching conditions. In addition, we discuss the most suitable propagation conditions that maximize the confinement of light power in the vicinity of the core-cladding interface for sensing purposes.