Stark Effect Research Articles

Characterization of Magnetized-Plasma System Induced by Laser

This study investigated the effect of applying an external magnetic field on the characteristics of laser-induced plasma, such as its parameters plasma, magnetization properties, emission line intensities, and plasma coefficients, for plasma induced from zinc oxide: aluminum composite (ZO:AL) at an atomic ratio of 0.3 %. Plasma properties include magnetization and emission line intensities. The excitation was done by a pulsed laser of Nd:YAG with 400 mJ energy at atmospheric pressure. Both the electron temperature and number density were determined with the help of the Stark effect principle and the Boltzmann-Plot method. There was a rise in the amount of (ne) and (Te) that was produced by applying a magnetic field and, on the other hand, using the 532 nm wavelength rather than the fundamental wavelength of a laser. The emission lines in the atmosphere's plasma have an appearance of Lorentzian shape. The 532 nm laser exhibited a decrease in both the Larmor radius and the confinement factor compared with the 1064 nm laser. By applying the magnetic field, the Laser Induced Breakdown Spectroscopy (LIBS) intensities increased by 1.44 times when compared to the emissions before applying the field. In addition, the spectral line intensities improved with the fundamental wavelength compared to the second harmonic frequency as a result of the increase in the extracted materials. This is due to the increase in the absorbance of the laser by the target, as some of these materials are excited, so they act as emission sources, which makes them more detectable.

Asymmetric conducting route and potential redistribution determine the polarization-dependent conductivity in layered ferroelectrics.

Precise control of the conductivity of layered ferroelectric semiconductors is required to make these materials suitable for advanced transistor, memory and logic circuits. Although proof-of-principle devices based on layered ferroelectrics have been demonstrated, it remains unclear how the polarization inversion induces conductivity changes. Therefore, function design and performance optimization remain cumbersome. Here we combine ab initio calculations with transport experiments to unveil the mechanism underlying the polarization-dependent conductivity in ferroelectric channel field-effect transistors. We find that the built-in electric field gives rise to an asymmetric conducting route formed by the hidden Stark effect and competes with the potential redistribution caused by the external field of the gate. Furthermore, leveraging our mechanistic findings, we control the conductivity threshold in α-In2Se3 ferroelectric channel field-effect transistors. We demonstrate logic-in-memory functionality through the implementation of electrically self-switchable primary (AND, OR) and composite (XOR, NOR, NAND) logic gates. Our work provides mechanistic insights into conductivity modulation in a broad class of layered ferroelectrics, providing foundations for their application in logic and memory electronics.

Stark effect and dissociation of mesons in holographic conductor

We study the meson spectrum of the N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{N} $$\\end{document} = 4 supersymmetric Yang-Mills theory with N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{N} $$\\end{document} = 2 fundamental hypermultiplets for a finite electric field by using the D3/D7 model. The spectrum for scalar and vector mesons is computed by analyzing the (quasi-)normal modes for the fluctuations of the D7-brane embedding and gauge fields. In the presence of an electric field, two different phases in the background are realized: the meson and dissociation phases. In this paper, we analyze the meson spectrum of scalar and vector mesons for all ranges of the electric field and explore the effect of the electric field on the meson spectrum, that is, the Stark effect. In the meson spectrum, we observe the avoided crossing between different levels due to the coupling of fluctuations via the electric field.

The Stark Effect: A Tool for the Design of High-Performance Molecular Rectifiers.

Molecular electronic devices offer a path to the miniaturization of electronic circuits and could potentially facilitate novel functionalities that can be embedded into the molecular structure. Given their nanoscale dimensions, device properties are strongly influenced by quantum effects, yet many of these phenomena have been largely overlooked. We investigated the mechanism responsible for current rectification in molecular diodes and found that efficient rectification is achieved by enhancing the Stark effect strength and enabling a large number of molecules to participate in transport. These findings provided insights into the operation of molecular rectifiers and guided the development of high-performance devices via the design of molecules containing polarizable aromatic rings. Our results are consistent for different molecular structures and are expected to have broad applicability to all molecular devices by answering key questions related to charge transport mechanisms in such systems.

Tunable Vernier Series-Coupled Microring Resonator Filters Based on InGaAs/InAlAs Multiple Quantum-Well Waveguide

We demonstrate a fourth-order Vernier serious-coupled microring resonator (MRR) filter based on the InGaAs/InAlAs five-layer asymmetric coupled quantum-well (FACQW) waveguide. As the tuning of the main resonance wavelength is driven by the electrorefractive index change in the FACQW layer caused by the quantum-confined Stark effect (QCSE), the MRR filter has lower tuning power consumption and high-speed operation. The free spectral range (FSR) of the MRR filter is extended to 9.4 nm. The main resonant peak is discretely tuned within one FSR, leading to an increase in the wavelength channel.

Structural and luminescence performance of the Eu3+ doped alkaline combined metal oxide-based sodium phosphate phosphors; NaMPO4 (M = Mg, Ba, and Ca) for LED applications

The present research module is about the synthesis of Eu3+ ions-doped NaMPO4(M = Mg, Ba, and Ca) phosphate phosphors by the solution combustion synthesis method. The phase formation and chemical structures of alkaline combined metal oxide-based sodium phosphate phosphors are characterised by X-ray powder diffraction (XRD) and FT-IR measurements. Optimized crystal geometries were generated by employing VESTA software. The crystallite size was calculated from the full width at half maximum (FWHM) of the diffraction peak using the Scherrer formula. G-Fourier transformation software (G-FT) was adopted for generating electron density mapping of NaMgPO4 phosphors, 2D mapping, and 3D chicken plots showing crystal sites occupied by the compound’s constituent elements. The particle size distribution was confirmed by XRD diffraction, and SEM analysis found approximately 12 μm. UV–visible and photoluminescence spectroscopy uncover the optical traits of the prepared phosphor. Photo-emissions of Eu3+doped alkaline combined metal oxide-based sodium phosphate phosphors were monitored at possible excitation wavelengths. The orange-red peak observed at 592 nm and 598 nm occurs due to 5D0-7F1 electric dipole transitions. The peak observed at 618 nm corresponds to the forbidden f-f transitions 5D0-7F2. It is worth mentioning that absorption bands originating from the corresponding 5D0-7F2 transition widen the band region; hence, the stark effect becomes complicated. A low-intensity peak of 688 nm was observed in the NaCaPO4 phosphors, attributed to the 5D0-7F3 transition. Chromaticity coordinates and energy level transitions may determine the colour emission materials. The CIE coordinates of NaMPO4:Eu3+phosphors exhibit reddish emission and find application in light-emitting diodes (LEDs) and illuminating displays.

Correction to: Calculated Stark widths of the triply charged argon ion Ar iv

Correction to: Calculated Stark widths of the triply charged argon ion Ar <scp>iv</scp>

Application of laser-induced breakdown spectroscopy for the analysis of pig bones

An application of the laser-induced breakdown spectroscopy technique (LIBS) for the elemental analysis of pig shoulder bone samples is reported. Measurements were performed using a compact laboratory-made LIBS system based on the TEA CO2 laser and time-integrated signal detection. The recorded spectra consisted of well-defined atomic and single-charged ionic lines of bone matrix elements (Ca and P) and other constituent elements (e.g. Mg, Zn, Na, K, and C) with a good signal-to-noise ratio suitable for chemical analysis. Based on the elemental composition of bone samples measured by inductively coupled plasma emission spectroscopy, limits of detection (LOD) of LIBS analysis were estimated for several elements. LOD ranged from 2.2 ppm (K) to 16 ppm (Zn). Carbon and Hα spectral lines were used for plasma diagnostics by measuring Stark widths. Optical profilometry was used to assess the capability of LIBS for depth profile analysis. For laser fluence between 13.0 and 18.2 J cm−2, the ablation rate per pulse ranged from 6 to 10 μm.

Onset of Quantum-Confined Stark Effects in Multijunction Photovoltaic Laser Power Converters Designed with Thin Subcells

Photovoltaic multijunction power-converting III–V semiconductor devices generate electrical power from the optical energy of laser beams. They exhibit conversion efficiencies reaching values greater than 60% and 50% for the GaAs and the InP material systems, respectively. The applications of optical wireless power transmission and power-over-fiber greatly benefit from employing such laser power converters constructed with multiple subcells; each is designed with either thin GaAs or InGaAs absorber regions. This study elucidates how the application of electric fields on thin heterostructures can create specific current–voltage characteristics due to modifications of the absorption characteristics from Franz–Keldysh perturbations and the onset of quantum-confined Stark effects. Negative differential photocurrent behavior can be observed as the reverse bias voltage is increased, until the corresponding current-clamping subcell reaches its reverse breakdown condition. The reverse voltage breakdown characteristics of the subcells were also measured to depend on the thickness of the subcell and on the optical intensity. The onset of the reverse breakdown was found to be at ~2.0–2.5 V under illumination and the thinner subcells exhibited higher levels of reverse bias currents. These effects can produce distinctive current–voltage behavior under spectrally detuned operations affecting the thinner subcells’ biases, but have no significant impact on the performance and maximum power point of multijunction power converters.

Polarization-matching and carrier confinement in III-nitride deep-ultraviolet light-emitting diodes

The polarization-induced quantum confined Stark effect has been recognized as a significant factor contributing to the Internal Quantum Efficiency (IQE) droop in light-emitting diodes (LEDs). This study focuses on the design of LEDs by investigating the InAlN/AlGaN interface. By incorporating InAlN quantum wells, a polarization-matched (PM) multi-quantum well (MQW) LED architecture was developed. While the flat conduction and valence bands on PM MQWs indicate an improved recombination rate, it is crucial to examine the impact on IQE, considering carrier confinement and injection efficiency influenced by the band offsets. This paper presents a numerical analysis comparing two LEDs emitting at 245 and 275 nm, respectively. The results demonstrate that the PM LED operating at 275 nm exhibits enhanced performance, benefiting from high probability density overlap. Conversely, the PM LED emitting at 245 nm demonstrates poor confinement, resulting in an overall low performance, regardless of polarization matching.

Experimental evidence of magnetic flux pumping in ASDEX upgrade

In high-β scenarios with on-axis co-current electron cyclotron current drive, which normally lowers q 0 below unity, the absence of sawteeth suggests the involvement of an additional current redistribution mechanism beyond neoclassical current diffusion. This is supported by imaging motional Stark effect diagnostic measurements, which indicate that q 0 remains consistently around 1. This phenomenon is observed in the presence of a 1/1 mode, indicating its potential role in the current redistribution. It is shown that the mode’s ability to modify the central current and suppress sawteeth increases with plasma pressure. These findings align with a recent theoretical model, which predicts a pressure threshold for sawtooth avoidance by a 1/1 quasi-interchange mode and where this threshold increases with the strength of inward current diffusion. Moreover, the advantages of the flux pumping scenario for future machines are highlighted.

Fabricating and investigating a beveled mesa with a specific inclination angle to improve electrical and optical performances for GaN-based micro-light-emitting diodes.

In this Letter, beveled mesas for 30 × 30 µm2 GaN-based micro-light-emitting diodes (µLEDs) with different inclination angles are designed, fabricated, and measured. We find that µLED with a mesa inclination angle of 28° has the lowest internal quantum efficiency (IQE) and the highest injection current density at which the peak IQE is obtained. This is due to the increased quantum confined Stark effect (QCSE) at the mesa edge. The increased QCSE results from the strong electric field coupling effect. Instead of radiative recombination, more nonradiative recombination and leakage current will be generated in the sidewall regions. Besides, the smallest angle (28°) also produces the lowest light extraction efficiency (LEE), which arises from the optical loss caused by the sidewall reflection at the beveled surface sides. Therefore, the inclination angle for the beveled mesa has to be increased to 52° and 61° by using Ni and SiO2 as hard masks, respectively. Experimental and numerical results show that the external quantum efficiency (EQE) and the optical power can be enhanced for the fabricated devices. Meanwhile, the reduced surface recombination rate also decreases the leakage current.

Electronic and optical properties of CdSe/ZnSe core/shell QDs within centered hydrogenic impurity and their tunability when subjected to an external electric field

The electronic and optical properties of CdSe/ZnSe semiconductor core/shell quantum dots with hydrogenic donor impurity were investigated theoretically. The perturbation approach and variational method were used in calculations under Effective Mass Approximation. The considered structure is embedded in a variable polymer matrix. The binding energy (BE), photoionization cross-section, polarizability, and diamagnetic susceptibility of the excited impurity were calculated first according to the core/shell radius ratio and then under a significant external electric field and in the absence of an external electric field. A significant stark shift was observed in the BE relative to the embedded matrix element.

Achieving atomically ordered GaN/AlN quantum heterostructures: The role of surface polarity.

Interface engineering in heterostructures at the atomic scale has been a central research focus of nanoscale and quantum material science. Despite its paramount importance, the achievement of atomically ordered heterointerfaces has been severely limited by the strong diffusive feature of interfacial atoms in heterostructures. In this work, we first report a strong dependence of interfacial diffusion on the surface polarity. Near-perfect quantum interfaces can be readily synthesized on the semipolar plane instead of the conventional c-plane of GaN/AlN heterostructures. The chemical bonding configurations on the semipolar plane can significantly suppress the cation substitution process as evidenced by first-principles calculations, which leads to an atomically sharp interface. Moreover, the surface polarity of GaN/AlN can be readily controlled by varying the strain relaxation process in core-shell nanostructures. The obtained extremely confined, interdiffusion-free ultrathin GaN quantum wells exhibit a high internal quantum efficiency of ~75%. Deep ultraviolet light-emitting diodes are fabricated utilizing a scalable and robust method and the electroluminescence emission is nearly free of the quantum-confined Stark effect, which is significant for ultrastable device operation. The presented work shows a vital path for achieving atomically ordered quantum heterostructures for III-nitrides as well as other polar materials such as III-arsenides, perovskites, etc.

Electric-Field Fluctuations as the Cause of Spectral Instabilities in Colloidal Quantum Dots.

Spectral diffusion (SD) represents a substantial obstacle toward implementation of solid-state quantum emitters as a source of indistinguishable photons. By performing high-resolution emission spectroscopy for individual colloidal quantum dots at cryogenic temperatures, we prove the causal link between the quantum-confined Stark effect and SD. Statistically analyzing the wavelength of emitted photons, we show that increasing the sensitivity of the transition energy to an applied electric field results in amplified spectral fluctuations. This relation is quantitatively fit to a straightforward model, indicating the presence of a stochastic electric field on a microscopic scale, whose standard deviation is 9 kV/cm, on average. The current method will enable the study of SD in multiple types of quantum emitters such as solid-state defects or organic lead halide perovskite quantum dots, for which spectral instability is a critical barrier for applications in quantum sensing.

Large scale fabrication of GaN nanorods template and characterization of MOCVD grown InGaN/GaN quantum wells on [formula omitted] plane of GaN nanorods

Gallium nitride (GaN) based low-dimensional optoelectronic devices offer distinct advantages over bulk counterparts owing to enhanced surface-to-volume ratio and better strain management. Among these devices, InGaN/GaN multi-quantum wells (MQWs) based on nanostructured GaN have garnered attention due to tunable bandgap along with reduced size for its possible integration into display technology. However, to mitigate the effects of polarization induced by polar planes of GaN, such as quantum confined stark effect, researchers are exploring the growth of MQWs on non-polar planes as a practical approach to improve emission characteristics and device performance. In this work, we present the fabrication of GaN nanorods (NRs) using a two-step etching method, followed by the growth of core-shell InGaN/GaN MQWs on the exposed non-polar {101‾0} sidewalls of GaN NRs. Our metrological studies confirmed the successful growth of InGaN/GaN MQWs on the non-polar sidewalls of strain-relaxed core GaN NRs. Furthermore, power-dependent luminescence study showed emission characteristics with absence of polarization-induced effects. Cathodoluminescence study validated the emission characteristics of InGaN/GaN MQWs grown on the exposed sidewalls of the GaN NRs.

Quadrupolar-dipolar excitonic transition in a tunnel-coupled van der Waals heterotrilayer.

Strongly bound excitons determine light-matter interactions in van der Waals heterostructures of two-dimensional semiconductors. Unlike fundamental particles, quasiparticles in condensed matter, such as excitons, can be tailored to alter their interactions and realize emergent quantum phases. Here, using a WS2/WSe2/WS2 heterotrilayer, we create a quantum superposition of oppositely oriented dipolar excitons-a quadrupolar exciton-wherein an electron is layer-hybridized in WS2 layers while the hole localizes in WSe2. In contrast to dipolar excitons, symmetric quadrupolar excitons only redshift in an out-of-plane electric field. At higher densities and a finite electric field, the nonlinear Stark shift of quadrupolar excitons becomes linear, signalling a transition to dipolar excitons resulting from exciton-exciton interactions, while at a vanishing electric field, the reduced exchange interaction suggests antiferroelectric correlations between dipolar excitons. Our results present van der Waals heterotrilayers as a field-tunable platform to engineer light-matter interactions and explore quantum phase transitions between spontaneously ordered many-exciton phases.

Numerical comparison of quantum-confined Stark effect on emission spectra between InP- and CdSe-based colloidal quantum dots

Numerical comparison of quantum-confined Stark effect on emission spectra between InP- and CdSe-based colloidal quantum dots

Signatures of the Optical Stark Effect on Entangled Photon Pairs from Resonantly Pumped Quantum Dots

Signatures of the Optical Stark Effect on Entangled Photon Pairs from Resonantly Pumped Quantum Dots

Binding Energy Stark-Shift, Polarizability and Dipole Moment Response of Shallow Donor Impurity in GaAs Quantum Dots

In this study, we have examined, under the influence of an electric field applied along the z-direction, the binding energy Stark-shift, the dipole moment and the polarizability of a confined shallow donor impurity in GaAs conical-shaped quantum dots (CSQD). With square infinite confinement system, the calculations are based on the approximation of the effective mass by using the finite difference method. Our results show that increasing the radius of the CSQD structure and the electric field intensity increases the Stark shift binding energy and it has a mixed behavior as a function of the impurity position. Furthermore, the polarizability and the dipole moment vary in a quasi-linear way as a function of the dot radius and they follow a decreasing function as a function of the electric field intensity. These two physical parameters have a double behavior, they decrease with the position of the impurity in the strong confinement regime and they increase in the top regions of the quantum dot. These results provide a lot of information about the behavior of the electronic wave function which give more interesting ideas for the fabrication of optoelectronic devices.