Harmonic Emission Research Articles

Resonance-affected high-order harmonic emission from atomic and molecular chromium laser-induced plasmas

The resonance enhancement of single-harmonic emission during the propagation of ultrafast pulses through chromium-contained plasmas is reexamined. We compare atomic (Cr) and molecular (Cr2O3, Cr3C2) plasmas to demonstrate a distinction in the enhancement factor of the single harmonic. We show how, in the case of 806 nm pump, the enhancement of the 29th harmonic (λ=27.8 nm) in Cr-contained plasma depends on the constituency of the plasma components at different conditions of target ablation. The application of tunable (1280–1440 nm) radiation allows the demonstration of notable variations of single harmonic (46 to 49 orders) enhancement using a two-color pump of Cr-contained plasma.

State of Charge Influence on the Harmonic Distortion From Electric Vehicle Charging

There is a general interest from manufacturers, users, regulation institutions, and research around electric vehicles development and its relation with the grid infrastructure. The penetration of electric vehicles in distribution networks brings considerable challenges in terms of power quality, particularly harmonic emissions. Such challenges are more evident in scenarios with high penetration of electric vehicles which consider the clustering effect in the charging process. Methodologies such as hosting capacity model electric vehicles as a constant power load with constant harmonic distortion along the entire charging process. This article presents the relationship between the charging algorithms of the electric vehicle chargers, the state of charge of the batteries, and the harmonic current distortion generated during the charging process. This model proposes that the harmonic current distortion depends on the state of charge of the battery and the charging algorithm of the vehicle. As this study would change meaningfully, the current studies of power quality related to electric vehicles, practical measurements in two charging stations, and offline simulations of the identified on-board chargers are shown to support the content of this article.

Electrospun fibers with highly polarized second harmonic light from 2-amino-4-nitroaniline and 3-nitroaniline nanocrystals embedded in poly-L-lactic acid polymer

Nanofibers consisting of organic optical nonlinear 2-amino-4-nitroaniline (2A4NA, C6H7N3O2) and 3-nitroaniline (3NA, C6H6N2O2) nanocrystals embedded in poly-l-lactic acid (PLLA) polymer were fabricated by the electrospinning technique. Intense anisotropic polarized second harmonic emission was observed from the molecular nanocrystals embedded within the nano and microfibers. The effective second-order susceptibility coefficients determined for the embedded 2A4NA and 3NA nanocrystals have magnitudes of 42 pmV−1 and 56 pmV−1 respectively, which are among the highest measured for organic nonlinear crystals. X-ray diffraction data revealed preferential crystallographic orientation of the molecules crystallized inside the nanofibers and calculations indicate average crystallite sizes of 33.5 nm and 21.7 nm, respectively for 2A4NA and 3NA. The present work follows previous studies on the nanofabrication, by the electrospinning technique, of polymer nanofibers doped with highly hyperpolarizable para-nitroaniline (C6H6N2O2) derivative push-pull molecules. These hybrid functional nano-systems display strong and directional nonlinear optical responses and establish the technique as a viable method for creating subwavelength scale generators of second harmonic light.

Three Phase Shunt Active Power Filter Using Simulink

In AC power grids for harmonic emission reduction and reactive power compensation, activity filters have become very common. The network with non-linear loads such as power converters is equipped with an active power filter for optimizing THD. Shunt type or series type. It also enhances voltage control and unbalance in flicks. For most active control filters, the instantaneous power principle also known as p-q theory is used. This paper explains Shunt active power filter for a 3-phase wire AC network. The proposed shunt active power filter uses principle of instantaneous reactive rower to remove harmonics from source streams. On the Matlab/Simulink method, the simulation results are shown.

Automatic Identification of Different Types of Consumer Configurations by Using Harmonic Current Measurements

Power quality (PQ) is an increasing concern in the distribution networks of modern industrialized countries. The PQ monitoring activities of distribution system operators (DSO), and consequently the amount of PQ measurement data, continuously increase, and consequently new and automated tools are required for efficient PQ analysis. Time characteristics of PQ parameters (e.g., harmonics) usually show characteristic daily and weekly cycles, mainly caused by the usage behaviour of electric devices. In this paper, methods are proposed for the classification of harmonic emission profiles for typical consumer configurations in public low voltage (LV) networks using a binary decision tree in combination with support vector machines. The performance of the classification was evaluated based on 40 different measurement sites in German public LV grids. This method can support network operators in the identification of consumer configurations and the early detection of fundamental changes in harmonic emission behaviour. This enables, for example, assistance in resolving customer complaints or supporting network planning by managing PQ levels using typical harmonic emission profiles.

Half-cycle waveform control for producing a broad and intense harmonic spectral continuum and an isolated attosecond pulse

An effective method to control the half-cycle harmonic emission process through the combination of multiple laser beams is proposed. The control process can be separated into three steps. In the first step, by properly choosing the chirp and the chirp delay of the fundamental pulse the relevant negative and positive half-cycle waveform for extending the harmonic cutoff can be obtained. In the second step, using either an asymmetric inhomogeneous field or a half-cycle unipolar pulse, the harmonic cutoff from the negative or the positive half-cycle waveform can be further extended. In the third step, by properly adding an ultraviolet pulse, the harmonic yield can be enhanced due to ultraviolet resonance ionization. Finally, by superposing some harmonics on the harmonic spectra, a number of isolated attosecond pulses shorter than 70 as can be obtained.

High-order harmonic generation by aligned heteronuclear diatomic molecules in an orthogonally polarized two-color laser field

Using the molecular strong-field approximation, we investigate high-order harmonic generation by heteronuclear diatomic molecules exposed to an orthogonally polarized two-color laser field, which consists of two mutually orthogonal linearly polarized fields with frequencies $$r\omega $$ and $$s\omega $$ . Here, r and s are integers and $$\omega $$ is the fundamental frequency. The harmonic emission rate and the harmonic ellipticity can be controlled using the laser-field parameters, in particular the relative phase and the intensity ratio of the laser-field components. The value of the relative phase, for which the emission rate is optimal, and the position of the cutoff can be estimated using a classical model. Also, we analyze the harmonic emission rate and the harmonic ellipticity as functions of the molecular orientation, which can also be used as a control parameter. Two types of minima are present in the spectra, depending on r and s. For $$r+s$$ even, interference minima are present in the spectra of the T-matrix component either parallel or perpendicular to the internuclear axis. Using quantum-orbit theory and the saddle-point method, we derive a condition for the interference minima, which relates the molecular orientation angle $$\theta _L$$ and the harmonic order n. The corresponding curves in the ( $$\theta _L$$ , n) plane well reproduce the minima of the numerically calculated spectra. For $$r+s$$ odd, minima are present in the spectra for a particular molecular orientation angle. These minima are explained using the explicit form of the T-matrix element. A heteronuclear as opposed to a homonuclear molecule affords a larger region in the parameter space where both the harmonic ellipticity and the harmonic intensity vary smoothly and both are large.

Self-starting harmonic comb emission in THz quantum cascade lasers

Harmonic comb states have proven to be ubiquitous in mid-IR quantum cascade lasers. We report here on robust, pure, self-starting harmonic mode locking in Copper-based double-metal THz quantum cascade lasers. Different harmonic orders can be excited in the same laser cavity depending on the pumping condition, and stable harmonic combs spanning more than 600 GHz at 80 K are reported. Such devices can be RF injected, and the free running coherence is assessed by means of a self-mixing technique performed at 50 GHz. A theoretical model based on Maxwell-Bloch equations including an asymmetry in the gain profile is used to interpret the data.

Power factor correction in power delivery systems with mutipulse nonlinear loads

THE PURPOSE. Мutipulse rectifiers are widely used as a nonlinear loads in industrial distribution systems. The advantage of mutipulse rectifiers is low harmonic emission and high power factor. However input currents of mutipulse rectifiers have a wide spectrum including characteristic and noncharacteristic harmonics. This has a negative impact on the power quality. Shunt capacitors are the simplest form of reactive power compensation in industrial power distribution systems. However power systems with nonlinear loads suffer from severe harmonic distortion due to the parallel resonance between capacitors and system inductance. Special compensating devices for reactive power compensation and correction of power system frequency response for resonances damping are necessary. METHODS. In this paper shunt compensating devices for power delivery systems with multipulse nonlinear loads are considered. Proposed devices are composed of 3-5 order parallel connected passive broadband filters. They provide power factor correction, voltage and current harmonics mitigation and resonance modes damping. A general broadband filter design procedure based on frequency and reactive power scaling of normalized filter parameters is developed. RESULTS. Characteristics of different compensating devices configurations using broadband passive filters are discussed. It is shown that broadband filtering devices enable compensation of fundamental frequency reactive power as well as mitigation of voltage harmonic level to values determined by Russian and international standards. Proposed devices have lower fundamental power losses in c omparing with known solutions. CONCLUSION. Proposed analytical design method is applicable to broadband filters of different orders.

A modified harmonic pricing scheme for customers based on quantifying the harmonic comprehensive contribution

The growing application of various types of nonlinear loads aggravates the harmonic distortion in distribution networks. To effectively address the harmonic issues, implementing an incentive pricing mechanism is a feasible solution. In this paper, a modified scheme is proposed to achieve fair and reasonable harmonic pricing for every customer. The scheme uses a new quantitative index for determining the harmonic comprehensive contribution without any prior assumptions about harmonic impedance. By aggregating multiple time scales and harmonic orders, this new index outperforms the traditional index in representing the overall harmonic distortion responsibility. Moreover, the proposed scheme introduces the harmonic metering price and the harmonic penalty price, and it aims to rationally evaluate the costs of energy metering and harmonic mitigation. The efficacy of the proposed scheme is verified by computer simulation and field test. The simulation and experimental results demonstrate that the proposed scheme is better than the conventional scheme to provide a fairer harmonic price and encourage customers to reduce harmonic emissions.

Controlling three-step harmonic emission for intense attosecond pulses using water window harmonic spectra

ABSTRACT Based on the three-step model of high harmonic generation, we propose a scheme to improve the harmonic spectra and to produce the intense water window attosecond pulses. It is found that, firstly, by introducing the single chirp and two chirps modulations, the instantaneous frequency on the falling part of the laser field is decreased. As a result, the electron can obtain larger energy during the acceleration-recombination process, showing a broad harmonic plateau in the water window region. Secondly, by properly adding a third controlling IR or UV pulse, the ionization process can be controlled and a larger ionization probability can be found, which leads to the enhancement of the harmonic intensity by 1 or 2 orders of magnitudes, respectively. Most important, using this scheme, the harmonic plateau is only contributed by the intense single harmonic emission peak, which can support the generation of an intense 36 as pulse.

Reexamining Different Factors of the Resonance-Enhanced High-Order Harmonic Generation in Atomic and Nanoparticle Laser-Induced Tin Plasmas

We reexamine the resonance enhancement of a single harmonic emission during the propagation of ultrafast pulses through atomic and nanoparticle tin-containing laser-induced plasma (LIP). We compare the single atomic Sn and Sn nanoparticle plasmas to demonstrate a distinction in the enhancement factor of the single harmonic in the case of fixed and tunable near-infrared pulses. The analysis of the dynamics of Sn LIP shows the range of optimal delays between heating and driving pulses (130–180 ns), at which the maximal harmonic yield can be achieved. The enhancements of the 17th and 18th harmonics of 806 nm pulses were analyzed in the case of single-color and two-color pumps of LIP, showing up to a 12-fold enhancement of even harmonics in the two-color pump case. We show the enhancement of a single harmonic in the vicinity of the 4d105s25p2P3/2→4d95s25p2 transitions of Sn II ions and demonstrate how this process depends on the constituency of the plasma components at different conditions of target ablation. The application of tunable (1280–1440 nm) radiation allows for demonstrating the variations of single harmonic enhancement using a two-color pump of Sn-containing LIP.

Two-dimensional phase cartography for high-harmonic spectroscopy

Extremely nonlinear spectroscopy based on high-order-harmonic generation has become a powerful investigation method for attosecond dynamics in gas and solid targets. In particular, the phase of harmonic emission was shown to carry profound insight into atomic and molecular structure and dynamics. However, current techniques offer phase measurements only along specific directions, thus providing partial characterization. Here we report on a new approach combining optical and quantum interferometers measuring along two dimensions the intensity and phase of harmonic emission from aligned molecules in the exact same experimental conditions. This two-dimensional cartography technique measures the phase with no arbitrary offset and no uncertainty on its sign. Measurements along different dimensions can be combined in two ways: either a single mapping or a redundant mapping allowing high-precision phase recovery using a Shack–Hartmann-like algorithm. We demonstrate both methods in a nitrogen test case, which allows disentangling structural and dynamical effects. Two-dimensional phase cartography paves the way to high-resolution high-harmonic spectroscopy for applications such as quantum orbital tomography and attosecond charge migration in molecules.

Parametric Simulation Studies on the Wave Propagation of Solar Radio Emission: The Source Size, Duration, and Position

Abstract The observed features of the radio source indicate that the waves of solar radio bursts are convoluted with complex propagation effects. In this work, we perform ray-tracing simulations on radio wave transport in the corona and interplanetary region with anisotropic electron density fluctuations. For the first time, the variation of the apparent source size, burst duration, and source position for the fundamental emission and harmonic emission at the frequency of 35 MHz are simulated as a function of the anisotropic parameter α and the angular scattering rate coefficient η = ϵ 2/h 0, where ϵ 2 = 〈δ n 2〉/n 2 is the density fluctuation level and h 0 is its correlation length near the wave excitation site. It is found that isotropic fluctuations produce a much larger decay time than a highly anisotropic fluctuation for fundamental emission. By comparing the observed duration and source size with the simulation results in the parameter space, we can estimate the scattering coefficient and the anisotropic parameter η = 8.9 × 10−5 km−1 and α = 0.719 with a point pulse source assumption. Position offsets due to wave scattering and refraction can produce the co-spatial of the fundamental and harmonic waves in the observation of some type III radio bursts. The visual speed due to the wave propagation effect can reach 1.5c for η = 2.4 × 10−4 km−1 and α = 0.2 for the fundamental emission in the sky plane, accompanied with large expansion rate of the source size. The direction of the visual speed is mostly identical to the direction of the offset, thus, for the observation aimed at obtaining the source position, the source centroid at the starting time is closer to the wave excitation site.

Voltage distortion in LED street lighting installations

The paper considers two power quality issues: voltage distortion and voltage drop along the pole lines of different LED street (road) lighting installations. The research includes three parts: (1) development of a novel model and the corresponding software for calculating voltage harmonics in the three-phase LED street lighting installations, where the load is nonsymmetrical and nonlinear. The model is based on the application of symmetrical components and the impedance per phase model. (2) Experiments on two sections of a pilot street lighting installation, one with 6 poles with neutral white and the other with 5 poles with warm white LED luminaires (the former were with conventional, and the latter with improved drivers regarding harmonic emissions). Their results were used to define harmonic characteristics of the LED luminaires and validate the model. (3) The developed software was applied to four typical street (road) lighting installations, two with a single-sided and two with a central pole layout. The major outcome was the determination of the maximum permissible number of the LED luminaires which can be connected to the feeding cable without exceeding any of the limits related to voltage drop, total voltage harmonic distortion and individual voltage harmonics in either the full or reduced street lighting regimes.

Strong-field physics in three-dimensional topological insulators

We investigate theoretically the strong-field regime of light-matter interactions in the topological-insulator class of quantum materials. In particular, we focus on the process of non-perturbative high-order harmonic generation from the paradigmatic three-dimensional topological insulator bismuth selenide (Bi$_2$Se$_3$) subjected to intense mid-infrared laser fields. We analyze the contributions from the spin-orbit-coupled bulk states and the topological surface bands separately and reveal a major difference in how their harmonic yields depend on the ellipticity of the laser field. Bulk harmonics show a monotonous decrease in their yield as the ellipticity increases, in a manner reminiscent of high harmonic generation in gaseous media. However, the surface contribution exhibits a highly non-trivial dependence, culminating with a maximum for circularly polarized fields. We attribute the observed anomalous behaviour to: (i) the enhanced amplitude and the circular pattern of the interband dipole and the Berry connections in the vicinity of the Dirac point; and (ii) the influence of the higher-order, "hexagonal warping" terms in the Hamiltonian, which are responsible for the hexagonal deformation of the energy surface at higher momenta. The latter are associated directly with spin-orbit-coupling parameters. Our results thus establish the sensitivity of strong-field driven high harmonic emission to the topology of the band structure as well as to the manifestations of spin-orbit interaction.

Harmonic Radio Emission in Randomly Inhomogeneous Plasma

Abstract In the present paper, we describe a theoretical model of the generation of harmonic emissions of type III solar radio bursts. The goal of our study is to fully take into account the most efficient physical processes involved in the generation of harmonic electromagnetic emission via nonlinear coupling of Langmuir waves in randomly inhomogeneous plasma of solar wind ( ). We revisit the conventional mechanism of coalescence of primarily generated and back-scattered Langmuir waves in quasihomogeneous plasma. Additionally, we propose and investigate another mechanism that generates harmonic emission only in a strongly inhomogeneous plasma: the nonlinear coupling of incident and reflected Langmuir waves inside localized regions with enhanced plasma density (clumps), in the close vicinity of the reflection point. Both mechanisms imply the presence of strong density fluctuations in plasma. We use the results of a probabilistic model of beam–plasma interaction and evaluate the efficiency of energy transfer from Langmuir waves to harmonic emission. We infer that harmonic emissions from a quasihomogeneous plasma are significantly more intense than found in previous studies. The efficiency of Langmuir wave conversion into electromagnetic harmonic emission is expected to be higher at large heliospheric distances for the mechanism operating in quasihomogeneous plasma and at small heliocentric distances for the one operating in inhomogeneous plasma. The evaluation of emission intensity in quasihomogeneous plasma may also be applied for type II solar radio bursts. The radiation pattern in both cases is quadrupolar, and we show that emission from density clumps may efficiently contribute to the visibility of harmonic radio emission.

Harmonic Testing Analysis of Light Emitting Diode (LED) Lamps based SNI IEC 61000-3-2 Standard

The use of LED lamps in Indonesia has increased since 2013 because of low power consumption and high efficiency. LED lamps are non-linear loads that cause harmonic distortion in the electric power system. Harmonic distortion can impact to overheating in magnetic core electrical equipment. Therefore, it is necessary to standardize the limits of the harmonic emission limits of LED lamps. In this study, the harmonics measurements of LED lamps of 22 samples from 10 brands, which include different types of EMI filters in the LED drivers, are carried out to analyze harmonic currents. Measurements in this study conducted using Teseq ProfLine 2105. The results of parameter testing of third and fifth-order harmonic currents, peak current phase angle, beginning current flow at 60 degrees, and end current at 90 degrees were analyze based on the criteria for class C SNI IEC 61000-3-2 standard. The results showed that the three samples used EMI filter inductor in the LED driver can minimize third-order harmonic currents and comply with all parameters.

Laser-induced processes with homonuclear diatomic molecules in orthogonally polarized two-color laser field

Using our theory which is based on the strong-field approximation we analyze high-order above-threshold ionization and high-order harmonic generation processes for the case of the homonuclear diatomic molecules exposed to an orthogonally polarized two-color (OTC) laser field. The OTC field represents a superposition of two linearly polarized fields with mutually orthogonal polarizations and different frequencies. We analyze the photoelectron energy spectra and the harmonic ellipticity as a function of the ratio of the intensities of the OTC laser-field components and the relative phase. Some combinations of the values of these parameters lead to the high-energy electrons, while the harmonic ellipticity depends strongly on the ratio of the intensities of the laser-field components. It is possible to find the value of this ratio for which the ellipticity of the emitted harmonics is large. The signes of ellipticity are opposite for the molecular orientations which are connected through the reflection with respect to the axis along the first OTC field component. This symmetry is explained using the expression which relates the T-matrix element and the harmonic ellipticity.

High-order harmonic generation in graphene: Nonlinear coupling of intraband and interband transitions

We investigate high-order harmonic generation (HHG) in graphene with a quantum master equation approach. The simulations reproduce the observed enhancement in HHG in graphene under elliptically polarized light [N. Yoshikawa et al, Science 356, 736 (2017)]. On the basis of a microscopic decomposition of the emitted high-order harmonics, we find that the enhancement in HHG originates from an intricate nonlinear coupling between the intraband and interband transitions that are respectively induced by perpendicular electric field components of the elliptically polarized light. Furthermore, we reveal that contributions from different excitation channels destructively interfere with each other. This finding suggests a path to potentially enhance the HHG by blocking a part of the channels and canceling the destructive interference through band-gap or chemical potential manipulation.