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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Ultrafast Control of Even-Order Harmonic Generation from Solids by an Intense Terahertz Field
摘要： Nonperturbative even-order harmonics, physically forbidden in centrosymmetric crystals, are observed from both insulator (diamond) and semiconductor (silicon) samples driven by IR pulses, when in addition an intense THz electric field is applied to the solid. The time-resolved study of the high-harmonic spectra with the temporal profile of the THz electric field suggests a transient THz-field-induced symmetry reduction. We also investigate the harmonics’ yields depending on the angles of the linear IR and THz polarizations with respect to the crystal axes. This work might pave the way for THz-based symmetry control in solids with important ramifications for petahertz electronics.
关键词： symmetry reduction,petahertz electronics,Nonperturbative even-order harmonics,THz electric field,centrosymmetric crystals
更新于2025-09-10 09:29:36
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[IEEE 2018 EMF-Med 1st World Conference on Biomedical Applications of Electromagnetic Fields (EMF-Med) - Split, Croatia (2018.9.10-2018.9.13)] 2018 EMF-Med 1st World Conference on Biomedical Applications of Electromagnetic Fields (EMF-Med) - Modeling of Joule heating in tissues induced by high- and low-voltage pulse combinations for gene electrotransfer
摘要： Gene electrotransfer is a promising technique for safe and efficient gene therapy. It relies on locally delivered electric pulses to transfer previously injected foreign DNA into the cell. Applied pulses tissue (electroporation) and concomitant heat generation due to Joule effect. In our study we used finite element method to calculate electric field and temperature distribution during typical electrotransfer pulsing protocol (i.e. combination of 100 microsecond high-voltage pulse and 400 millisecond low-voltage pulse with pulse lag time of 1 second) in isotropic tissue (e.g. liver) and anisotropic tissue (e.g. skeletal muscle). For parallel plate electrodes results show negligible temperature rise in tissue bulk due to high voltage pulse and up to a few °C rise due to the low-voltage 400 ms-long pulse, depending on tissue conductivity.
关键词： COST EMF-MED,gene therapy,Joule heating,FEM,electric field,electroporation,gene electrotransfer
更新于2025-09-10 09:29:36
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Improvement of the third order nonlinear optical properties of nematic liquid crystal under the influence of different compositional percentage of doped SWCNT and the external electric field
摘要： In this research, the nematic liquid crystal (NLC) was doped with varying concentration (0-1 % wt.) of single walled carbon nanotubes (SWCNTs) at room temperature to study the nonlinear optical (NLO) properties of E5CN7@CNT cell.The third order NLO properties such as the nonlinear susceptibility, the nonlinear refraction (NLR) and the nonlinear absorption (NLA) were determined by using Z-scan techniques. The nonlinear studies have been done using a continuous wave (CW) He: Ne laser at 632.8 nm.Doping SWCNTs to eutectic uniaxial NLC (E5CN7) enhanced the third order nonlinear susceptibility, ??(3) and consequently the nonlinearity properties of composite systems improved.It is found that at lower concentration of CNTs (c< 0.75 % wt.), the third order nonlinear susceptibility are increased, but for concentration 0. 5<c<1 % wt., the third order nonlinear susceptibility are decreased. The negative sign of the observed NLR index, indicates that the E5CN7@CNT exhibits self-defocusing type optical nonlinearity. The two photon absorption (TPA) behavior, corresponding to negative sign NLA of samples. The reorientation of samples molecules amplifies upon the application of electric field, then nonlinearity increases.
关键词： Composite materials,Nematic liquid crystal,Carbon nanotubes,Third order nonlinear susceptibility,Nonlinear optics,Electric field,Z-scan method
更新于2025-09-10 09:29:36
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European Microscopy Congress 2016: Proceedings || Imaging of Electric Fields with the pnCCD (S)TEM Camera
摘要： The imaging of electric fields with the pnCCD (S)EM camera allows for the fast, direct, and precise measurement of electric fields in various materials. Techniques providing fast, direct, and precise measurement of the electric field distribution are of great interest for modern materials research. We present a fast, direct, and precise measurement of the electric field distribution in the nanometer scale with the pnCCD (S)EM camera. With this technique, small shifts of the bright field image due to the electric field can be detected with a precision of less than 1 nm. The large number of pixels (264 × 264) allows for the simultaneous measurement of the electric field in a large area. The fast readout (1.2 kHz) enables the observation of dynamic processes. The direct measurement of the electric field avoids the need for complex simulations or indirect methods. The pnCCD (S)EM camera is thus a powerful tool for the investigation of electric fields in materials.
关键词： SEM,electric field,imaging,pnCCD,nanometer scale
更新于2025-09-10 09:29:36
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Roll-to-Roll (R2R) Production of Ultrasensitive, Flexible, and Transparent Pressure Sensors Based on Vertically Aligned Lead Zirconate Titanate and Graphene Nanoplatelets
摘要： Despite extensive advances in the use of piezoelectric materials in flexible electronics, they have numerous shortcomings, including low efficiency, limited flexibility, and lack of transparency. Additionally, the production of these materials is often limited to small batch processes which are difficult to scale up for mass production. A novel method to produce ultrasensitive, high performance, flexible, and transparent piezoelectric materials where both lead zirconate titanate nanoparticles, and graphene nanoplatelets are aligned together in polydimethylsiloxane under an AC electric field in the thickness (“Z”) direction, is reported here for the first time. The electric field alignment improves the piezoelectric response along with transparency and also reduces the amount of filler required to achieve outstanding piezoelectric properties. The resulting ultrasensitive piezoelectric film is able to sense the pressure of a bird feather (1.4 mg) dropped from a certain distance, whereas at the touch of a fingertip, it can generate up to 8.2 V signal. Moreover, the mass production compatibility of the system is also demonstrated by producing a 3 m long and 15 cm wide large-area sample via a novel 44′ long roll-to-roll manufacturing line which is designed and developed by the group.
关键词： piezoelectric pressure sensor,flexible and transparent sensors,electric field–induced alignment,roll-to-roll manufacturing,PZT and graphene nanoplatelets
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Generating Electric Fields for Air Sensitivity Measurement of Specific Absorption Rate Probe
摘要： To measure the air sensitivity of a specific absorption rate (SAR) probe, an electric field (E-field) generation system is implemented using field-generating cells, a transverse electromagnetic (TEM) cell below 1 GHz and waveguides in 1.12–2.6 GHz-frequency range. The output side of the field-generating cells is terminated with an attenuator and a power sensor to determine the E-field strength which is traceable to power and attenuation standards. Measured results with the estimated uncertainty are presented at 835 MHz and 1800 MHz.
关键词： waveguide,uncertainty,Electric field,specific absorption rate,measurement standards,TEM cell
更新于2025-09-10 09:29:36
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - High-Intensity Electric Field Measurements with Rydberg Vapors
摘要： Measurements of radio-frequency (RF) electric fields using EIT spectroscopy of Rydberg states in atomic vapors have garnered significant interest in recent years. Here we describe recent work extending the approach to measurements of high-intensity RF electric fields above 1 kV/m and continuous-frequency RF measurement capability.
关键词： RF,metrology,electric field measurements,quantum sensors,Rydberg atoms
更新于2025-09-10 09:29:36
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Symmetry Modulation and Enhanced Multiferroic Characteristics in Bi <sub/>1-</sub><i> <sub/>x</sub></i> Nd <i> <sub/>x</sub></i> FeO <sub/>3</sub> Ceramics
摘要： BiFeO3 is recognized as the most important room temperature single phase multiferroic material. However, the weak magnetoelectric (ME) coupling remains as a key issue, which obstructs its applications. Since the magnetoelectric coupling in BiFeO3 is essentially hindered by the cycloidal spin structure, here efforts to improve the magnetoelectric coupling by destroying the cycloidal state and switching to the weak ferromagnetic state through symmetry modulation are reported. The structure is tuned from polar R3c to polar Pna2 1, and finally to nonpolar Pbnm by forming Bi1-xNdxFeO3 solid solutions, where two morphotropic phase boundaries (MPBs) are detected. Greatly enhanced ferroelectric polarization is obtained together with the desired weak ferromagnetic characteristics in Bi1-xNdxFeO3 ceramics at the compositions near MPBs. The change of magnetic state from antiferromagnetic (cycloidal state) to ferromagnetic (canted antiferromagnetic) is confirmed by the observation of magnetic domains using magnetic force microscopy. More interestingly, combining experiments and first-principles-based simulations, an electric field-induced structural and magnetic transition from Pna21 back to R3c is demonstrated, providing a great opportunity for electric field-controlled magnetism, and this transition is shown to be reversible with additional thermal treatment.
关键词： multiferroics,symmetry modulation,electric field-controlled magnetism,BiFeO3
更新于2025-09-10 09:29:36
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On the influence of dilute charged impurity and perpendicular electric field on the electronic phase of phosphorene: Band gap engineering
摘要： Tuning the band gap plays an important role for applicability of 2D materials in the semiconductor industry. The present paper is a theoretical study on the band gap engineering using the electronic density of states (DOS) of phosphorene in the presence of dilute charged impurity and of a perpendicular electric field. The electronic DOS is numerically calculated using a combination of the continuum model Hamiltonian and the Green’s function approach. Our findings show that the band gap of phosphorene in the absence and presence of the perpendicular electric field decreases with increasing impurity concentration and/or impurity scattering potential. Further, we found that in the presence of opposite perpendicular electric fields, the electronic DOS of disordered phosphorene shows different changing behaviors stemming from the Stark effect: in the positive case the band gap increases with increasing electric-field strength; whereas in the negative case the band gap disappears. The latter, in turn, leads to the semiconductor-to-semimetal and semiconductor-to-metal phase transition for the case of strong impurity concentrations and strong impurity scattering potentials, respectively. The results can serve as a base for future applications in logic electronic devices.
关键词： Stark effect,perpendicular electric field,semiconductor-to-semimetal transition,phosphorene,band gap engineering,electronic density of states,semiconductor-to-metal transition,dilute charged impurity
更新于2025-09-10 09:29:36
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Electric field induced Lyman- <i>α</i> emission of a hydrogen beam for electric field measurements
摘要： Electric field induced Lyman-α emission is a new way of measuring weak electric fields in vacuum and in a plasma. It is based on the emission of Lyman-α radiation (121.6 nm) by a low-energy metastable H atom beam due to Stark-quenching of the 2s level induced by the field. In this paper, we describe the technique in detail. Test measurements have been performed in vacuum between two plates polarized at a controlled voltage. The intensity of emitted radiation, proportional to the square of the field modulus, has been recorded by a lock-in technique, which gives an excellent signal to noise ratio. These measurements provide an in situ calibration that can be used to obtain the absolute value of the electric field. A diagnostic of this type can help to address a long standing challenge in plasma physics, namely, the problem of measuring electric fields without disturbing the equilibrium of the system that is being studied.
关键词： Electric field,hydrogen beam,plasma physics,Stark-quenching,Lyman-α emission
更新于2025-09-10 09:29:36