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- anharmonic Bloch oscillations
- coupled mode method
- array of waveguides
- active harmonic filter
- Multifunctional VSC
- unity power factor operation
- power quality improvement
- grid-connected SPV system
- renewable energy sources
- Optoelectronic Information Science and Engineering
- Electrical Engineering and Automation
- Shevchenko Pridnestrovskii State University
- Malaviya National Institute of Technology
- Academy of Sciences of Moldova
- IIITD&M Kancheepuram
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High-<formula><tex>$T_\rm{c}$</tex></formula> Superconducting Fourth-Harmonic Mixer using a Dual-Band Terahertz On-Chip Antenna of High Coupling Efficiency
摘要： This paper presents a dual-band on-chip antenna coupled high-Tc superconducting (HTS) Josephson-junction sub-terahertz (THz) fourth-harmonic mixer. The antenna utilizes a couple of different structured twin-slots to enable the resonant radiations at two frequencies, and integrates a well-designed coplanar waveguide (CPW) network for achieving good radiation coupling and signal isolation characteristics. The electromagnetic (EM) simulations show that coupling efficiencies as high as -4 dB and -3.5 dB are achieved for the 160-GHz and 640-GHz operating frequency bands, respectively. Based on this dual-band antenna, a 640-GHz HTS fourth-harmonic mixer is developed and characterized in a range of operating temperatures. The mixer exhibits a measured conversion gain of around -18 dB at 20 K and -22 dB at 40 K respectively. The achieved intermediate-frequency (IF) bandwidth is larger than 23 GHz. These are the best results reported for HTS harmonic mixers at comparable sub-THz frequency bands to date.
关键词： high-temperature superconductor Josephson junction,dual-band on-chip antenna,terahertz wireless applications,fourth-harmonic mixing,Terahertz mixer
更新于2025-09-23 15:23:52
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RF Characterization of NiO and TiO <sub/>2</sub> Based Metal-Insulator-Metal (MIM) Diodes on Flexible Substrates
摘要： This paper presents the fabrication and characterization of metal-insulator-metal (MIM) diodes on flexible substrates for RF and microwave circuit applications. Diodes using two types of insulators, titanium dioxide (TiO2) and nickel oxide (NiO), are investigated. These insulators are obtained using different oxidation techniques, i.e., in-situ oxidation for TiO2 and plasma oxidation for NiO. Asymmetric metal contacts (Ti-TiO2-Pd and Ni-NiO-Mo) are utilized to achieve nonlinear I–V characteristics. The fabricated diodes show strong non-linearity, high current densities, and low turn-ON voltage. The diodes show RF to dc rectification with near-ideal behavior and rectification sensitivity of 22 V/W (18 GHz) and 46 V/W (18 GHz) for TiO2 and NiO, respectively. NiO-based diodes barrier shows higher current density and higher cutoff frequency in comparison with TiO2 as expected diodes due to thinner oxide and lower dielectric constant. The diodes also work well as frequency doublers over a wide frequency range of 1–4 GHz for TiO2 and 2–10 GHz for NiO-based diodes. Good dc and RF performance of diodes indicate that good quality oxide can be achieved on plastic substrates and MIM devices can provide a perfect solution for RF and microwave circuits on a flexible substrate.
关键词： MIM diodes,rectification,Flexible electronics,harmonic generation,thin film devices,microwave circuits
更新于2025-09-23 15:23:52
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Local structural changes due to the electric field-induced migration of oxygen vacancies at Fe-doped SrTiO <sub/>3</sub> interfaces
摘要： We report on our study of dc voltage-induced structural changes at reduced and oxidized Fe-doped SrTiO3 (Fe:STO) electrode interfaces using second harmonic generation (SHG) together with photoluminescence (PL) method. We show that oxygen vacancy defects play a critical role in determining the local electrical and structural properties of interfacial depletion regions at Schottky junctions. The SHG results show that the dc electric field causes oxygen ions and vacancies to displace toward the anode and cathode in the low field regime, respectively. This process forms electrostrictive distortions within local interfacial depletion regions which are described by Fe:Ti-O bond stretching and bending. Differences in the EFISHG responses from the oxidized and reduced crystal interfaces are explained according to local oxygen vacancy concentrations and dynamics and their effects on the Schottky barrier heights and depletion region widths at each interface. These results are further supported by our PL measurements. Oxygen ion migration towards the Fe:STO surface leads to enhanced fluorescence intensities from in-gap acceptor states. We demonstrate that SHG and PL measurements are well suited for understanding and resolving the underlying causes of dielectric breakdown processes and device failure brought on by dc electric field and ionic defect migrations in perovskite-type electroceramics.
关键词： Photoluminescence,Oxygen Vacancy,Electroceramic,Second Harmonic Generation
更新于2025-09-23 15:23:52
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Enhanced Second Harmonic Generation from Ferroelectric HfO <sub/>2</sub> -Based Hybrid Metasurfaces
摘要： Integrated nonlinear metasurfaces leading to high-efficiency optical second harmonic generation (SHG) are highly desirable for optical sensing, imaging, and quantum photonic systems. Compared to traditional metal-only metasurfaces, their hybrid counterparts, where a non-centrosymmetric nonlinear photonic material is incorporated in the near field of a metasurface, they can significantly boost SHG efficiency. However, it is difficult to integrate such devices on-chip due to material incompatibilities, thickness scaling challenges and the narrow band gaps of nonlinear optical materials. Here, we demonstrate significantly enhanced SHG in on-chip integrated metasurfaces by using nanometer thin films of ferroelectric Y:HfO2. This material has the merit of CMOS compatibility, ultra-violet transparency up to 250 nm and significant scalability down to sub 10 nm when deposited on silicon. We observe a twenty times magnitude enhancement of the SHG intensity from the hybrid metasurface compared to a bare ferroelectric HfO2 thin film. Moreover, a 3-fold SHG enhancement is observed from the hybrid metasurface compared to a control structure using non-ferroelectric HfO2, demonstrating a major contribution to the SHG signal from ferroelectric Y:HfO2. The effective second-order nonlinear optical coefficient χ(2) of Y:HfO2 is determined to be 6.0 ± 0.5 pm/V, which is comparable to other complex nonlinear photonic oxide materials. Our work provides a general pathway to build an efficient on-chip nanophotonic nonlinear light source for SHG using ferroelectric HfO2 thin films.
关键词： second harmonic generation (SHG),nonlinear photonics,metasurface,plasmonics,ferroelectric Y:HfO2
更新于2025-09-23 15:23:52
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Reshaping the Second-Order Polar Response of Hybrid Metal–Dielectric Nanodimers
摘要： We combine the field confinement of plasmonics with the flexibility of multiple Mie resonances by bottom-up assembly of hybrid metal-dielectric nanodimers. We investigate the electromagnetic coupling between nanoparticles in heterodimers consisting of gold and barium titanate (BaTiO3 or BTO) nanoparticles through nonlinear second-harmonic spectroscopy and polarimetry. The overlap of the localized surface plasmon resonant dipole mode of the gold nanoparticle with the dipole and higher-order Mie resonant modes in the BTO nanoparticle lead to the formation of hybridized modes in the visible spectral range. We employ the pick-and-place technique to construct the hybrid nanodimers with controlled diameters by positioning the nanoparticles of different types next to each other under a scanning electron microscope. Through linear scattering spectroscopy, we observe the formation of hybrid modes in the nanodimers. We show that the modes can be directly accessed by measuring the dependence of the second-harmonic generation (SHG) signal on polarization and wavelength of the pump. We reveal both experimentally and theoretically that the hybridization of plasmonic and Mie-resonant modes leads to a strong reshaping of the SHG polarization dependence in the nanodimers, which depend on the pump wavelength. We compare the SHG signal of each hybrid nanodimer with the SHG signal of single BTO nanoparticles to estimate the enhancement factor due to the resonant mode coupling within the nanodimers. We report up to two orders of magnitude for the SHG signal enhancement compared to isolated BTO nanoparticles.
关键词： Dielectrics,Second-harmonic generation,Barium Titanate,Polar-dependence,Hybrid nanoantennas,Plasmonics
更新于2025-09-23 15:23:52
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High order harmonic generation in solids: a review on recent numerical methods
摘要： Interaction of intense lasers with solid materials offers an alternative way to achieve high-order harmonic generation (HHG). Since the underlying mechanisms of the harmonic emission remain uncertain, a large number of theoretical studies have been proposed to explain the experimental findings in this fast-growing field. Here, we review the primary numerical methods and present a brief perspective of HHG in solids.
关键词： Ultrafast laser,strong field,numerical simulations,laser-crystal interaction,solid materials,high-order harmonic generation
更新于2025-09-23 15:23:52
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Dynamical distortions of structural signatures in molecular high-order harmonic spectroscopy
摘要： We study the signature of two-center interferences in molecular high-order harmonic spectra, with an emphasis on the spectral phase. With the help of both ab initio computations based on the time-dependent Schr?dinger equation and the molecular strong-field approximation (SFA) as developed by Chiril? et al. [Phys. Rev. A 73, 023410 (2006)] and Faria [Phys. Rev. A 76, 043407 (2007)], we observe that the phase behavior is radically different for the short and the long trajectory contributions. By means of Taylor expansions of the molecular SFA, we link this effect to the dynamics of the electron in the continuum. More precisely, we find that the value of the electric field at recombination time plays a crucial role in the shape of the destructive interference phase jump.
关键词： molecular spectroscopy,spectral phase,strong-field approximation,two-center interferences,time-dependent Schr?dinger equation,high-order harmonic generation
更新于2025-09-23 15:23:52
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Parametric Study and Optimization of Linear and Nonlinear Vibration Absorbers Combined with Piezoelectric Energy Harvester
摘要： In this work, a harmonically excited generalized two degree of freedom non-linear system is used to manifest the functions of both the vibration absorber and energy harvester simultaneously. The generalized system has been reduced to a linear primary system with linear/nonlinear absorber and harvester or nonlinear primary system with linear/nonlinear absorber and harvester. Multi-harmonic balance method (MHBM) along with arc length continuation is used for generating frequency response plots for different absorber and energy harvester system parameters with constant primary system parameters and excitation amplitude. The frequency response plots show multiple branches of stable periodic solutions and jump at certain frequency ranges for systems with nonlinearity. The absorber and energy harvester parameters are optimized using an optimization procedure based on genetic algorithm in combination with response surface methodology. The method is validated with analytical solutions available in the literature for a linear primary system with linear absorber and harvester and nonlinear primary system with nonlinear absorber alone. This study demonstrates that the proposed optimization framework along with MHBM is suitable for generating the optimal frequency response for multifunctional energy harvesting systems or systems with nonlinear absorber. The frequency response plots with optimal parameter values reiterates the fact that the absorber system with nonlinear element perform better compared to its linear counterpart over a wider band of frequencies. The study also reports the comparison of the performance of a combined nonlinear absorber harvester system with that of a nonlinear energy sink (NES) absorber harvester system.
关键词： vibration absorber,multi-harmonic balancing,energy harvesting,optimization,response surface method,genetic algorithm
更新于2025-09-23 15:23:52
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[IEEE 2018 International Conference and Exposition on Electrical And Power Engineering (EPE) - Iasi, Romania (2018.10.18-2018.10.19)] 2018 International Conference and Exposition on Electrical And Power Engineering (EPE) - Aspects Regarding Disturbances Produced by Fluorescent Tubes
摘要： This paper has a strong applicative character. There is presented a modern system for monitoring dynamic states, carried out with the help of a data acquisition board. It is insisted upon an original monitoring program conceived by the paper team. There are presented then two applications of using this system: a) (experimental) analysis of disturbances produced by a fluorescent tube; b) analysis of disturbances produced by a LED tube. A special attention is paid to the experimental aspects which emphasize the waveforms of the currents corresponding to some fluorescent tubes (in a few representative operation states). Finally, there are presented conclusions, which have been obtained by finalizing the research and the afferent bibliography.
关键词： LED tube,harmonic analysis,test,fluorescent tube,disturbances
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - A versatile harmonic balance method in a parallel framework
摘要： In this paper, we present a parallelized and versatile harmonic balance approach for modeling the small-signal and large-signal frequency-domain response of the coupled semiconductor drift-diffusion equations used in TCAD device simulations. Our approach begins with a time-domain TCAD code, and we describe the process to adapt the system into the frequency domain so that the transformation can be parallelized. Both small-signal and large-signal analyses are easily simultaneously incorporated. Furthermore, we introduce the Isofrequency Remapping Scheme, so that an arbitrary number of high frequencies can be analyzed without introducing a prohibitive expense. Results obtained by our small-signal and large signal harmonic balance methods are shown to capture the same response for a linear device, as expected. Further results use our harmonic balance method to explore a prohibitively expensive time-domain problem: a large-signal, two-tone simulation too costly for a time-domain analysis, for which we are able to produce the expected response with intermodulation.
关键词： TCAD,parallelization,frequency-domain analysis,frequency mapping method,harmonic balance method
更新于2025-09-23 15:22:29