Mid-infrared electric field sampling approaching single-photon sensitivity

We theoretically investigate high-order harmonic generation in a spatially inhomogeneous field with mid-infrared driving wavelength and few-cycle duration. It is found that this spatiotemporally synthesized electric field is powerful to control the quantum path; as a result an ultra-broadband supercontinuum with bandwidth over 300 eV can be obtained successfully. Important characteristics of the attosecond pulse generation, including temporal envelope, harmonic chirp and carrier–envelope phase (CEP) dependence are further discussed. The results show that close-to-Fourier-limit 27 as isolated pulses are straightforwardly filtered from the supercontinuum. Moreover, such short isolated attosecond pulses can be supported by nearly all the CEPs of the laser electric field. This would open a way to obtain broadband isolated attosecond pulses with no need of CEP stabilization of the laser field.

Carbon nanotubes (CNTs) enable large electric field enhancement for an extremely broad bandwidth spanning from the optical domain down to static fields. This is due to their high aspect ratio, small tip radius, and high structural stability. CNTs therefore represent an ideal model-system for the investigation of nonlinear and strong-field phenomena. In this paper, we extend the range of optical-field-emission materials from metal nanostructures to CNTs. Quiver-quenched optical-field-emission (i.e., the transition to a sub-cycle regime) is observed for CNTs tips in a short-wavelength laser field of 820 nm that requires a mid-infrared excitation field of conventional metal tips emitters. This special property relies on the ultrasmall tips radius (∼1 nm) and the high optical-field enhancement (∼21.6) properties of CNTs. This study suggests that CNTs are excellent candidates for optically driven ultrafast electron sources with both high spatial and high temporal coherence. They also provide more freedom for the manipulation and control of electron dynamics at the attosecond timescale, which extends the bandwidth of light-wave electronic devices.

Resonant ultrafast excitation of infrared-active phonons is a powerful technique to control the electronic properties of materials, leading to remarkable phenomena such as light-induced enhancement of superconductivity1,2, switching of ferroelectric polarization3,4 and ultrafast insulator to metal transitions5. Here we show that light-driven phonons can be utilized to coherently manipulate macroscopic magnetic states. Intense mid-infrared electric field pulses, tuned to resonance with a phonon mode of the archetypical antiferromagnet DyFeO3, induce ultrafast and long-living changes of the fundamental exchange interaction between rare-earth orbitals and transition metal spins. Non-thermal lattice control of the magnetic exchange, defining the very stability of the macroscopic magnetic state, allows us to perform picosecond coherent switching between competing antiferromagnetic and weakly ferromagnetic spin orders. Our discovery emphasizes the potential of resonant phonon excitation for the manipulation of ferroic order on ultrafast timescales6.

In the near field region, optical antennas can generate local hot spots with high energy density. It can be very useful in increasing the photon-matter interactions for bio-sensing applications. There are several important bio-molecules having signature frequency (vibrational resonance) matching the mid infrared region of the optical spectrum. Thus mid-infrared antenna integrated with Quantum cascade laser (QCL) is highly desirable as it is currently considered to be one of the most efficient mid-infrared laser sources with a huge gamut of commercial applications. Here, we present a novel metal-dielectric-metal (MDM) based plasmonic nanorod antenna integrated on the facet of a room temperature working Quantum Cascade Laser. Simulations showed that at an optimized SiO₂ thickness of 20nm, the antenna can generate a local electric field with intensity 500 times higher than the incident field intensity. Further, it can increase the number of regions with local hot spots due to a higher number of geometrical singularities or sharp edges present in the MDM structure. This feature can be extremely useful, especially for bio-sensing applications. All device structures have been optimized based on 3d finite-difference timedomain (FDTD) numerical simulations. The antenna was fabricated on the facet of QCL using focused ion beam (FIB). The integrated plasmonic QCL has been measured using an apertureless mid-infrared near field scanning optical microscopy (a-NSOM). The measurement set-up is based on an inverted microscope coupled with a commercially available Atomic Forced Microscopy (AFM). We have experimentally found that such integrated nano antenna can generate a very narrow optical spot size, much below the diffraction limit, with high power density that matches well with the simulation results.

The transient electroluminescence (EL) technique is widely used to evaluate the carrier mobility in the field of organic light emitting diodes. The traditional analog detection strategy using oscilloscopes is generally limited since the background noise causes an underestimation of the mobility value. In this paper, we utilize time-correlated single-photon counting (TCSPC) to probe the transient EL for mobility calculation. The measurements on tris(8-hydroxyquinoline) aluminum (Alq3) show that the electron mobilities obtained using the TCSPC technique are slightly higher than those obtained from the analog method at all the investigated voltages. Moreover, the TCSPC mobilities demonstrate weaker dependence on the root of electrical field compared to the oscilloscope mobilities. These improvements are attributed to the unique principle of TCSPC, which quantifies the EL intensity by counting the number of single-photon pulses, improving its single-photon sensitivity and eliminating the negative impacts of electrical noise. These advantages make TCSPC a powerful technique in the characterization of time-resolved electroluminescence.Graphical

Three types of structures which can exist in planar SmC* samples, depending on sample thickness are described. Two critical thicknesses limiting the existence of the twisted nonhelical configuration are defined. Behaviour of this structure in an electric field is theoretically solved for simplified anchoring conditions. The critical field for the transition of the twisted structure to the homogeneous one is determined as a function of sample thickness, comparing the free energies of both structures Description de trois types de structures pouvant exister dans les echantillons de SmC* planaires en fonction de l'epaisseur de l'echantillon. Definition de deux epaisseurs critiques limitant l'existence de la configuration nonhelicoidale en torsion. Etude theorique du comportement de cette structure sous champ electrique pour des conditions d'ancrage simplifie. Determination en fonction de l'epaisseur de l'echantillon de la valeur critique du champ electrique pour la transition entre la structure avec torsion et la structure homogene

The electron-hole plasma in intrinsic InSb at 300 K can be compressed by electric and magnetic fields. In the theta-pinch configuration one applies, by a capacitor discharge over a one-winding coil around the sample, a magnetic field (0, 0,B z), which induces an electric field (0,E φ, 0); both fields cause the ambipolar motion (v r, 0, 0) of the plasma. We describe the electron-hole plasma by means of a magnetohydrodynamical two-fluid model. The resulting system of differential equations is solved numerically under the assumptions of scalar hydrodynamic pressure and field-independent mobilities. The influence of the plasma properties on the theta pinch is studied as well as the dependence on the experimental conditions like radius of the sample, maximum value and risetime of the magnetic field.

We propose using matrix-isolated paramagnetic diatomic molecules to search for the electric dipole moment of the electron (eEDM). As was suggested by Shapiro in 1968, the eEDM leads to a magnetization of a sample in the external electric field. In a typical condensed matter experiment, the effective field on the unpaired electron is of the same order of magnitude as the laboratory field, typically about 10(5) V/cm. We exploit the fact that the effective electric field inside heavy polar molecules is on the order of 10(10) V/cm. This leads to a huge enhancement of the Shapiro effect. Statistical sensitivity of the proposed experiment may allow one to improve the current limit on eEDM by 3 orders of magnitude in a few hours accumulation time.

The passage of a relativistic charged particle beam bunch through a structure is accompanied by transient electromagnetic fields. By causality, these fields must be behind the bunch, and are called "wakefields." The wakefields act back on the beam, and cause instabilities such as the beam break-up instability, and the headtail instability, which limit the luminosity of linear colliders. The wakefields are particularly important for short bunches with high charge. A great deal of effort is devoted to analytical and numerical calculations of wakefields, and wakefield effects. Experimental numbers are needed. In this thesis, we present measurements of the transient electric fields induced by a short high-charge electron bunch passing through a 6-way vacuum cross. These measurements are performed in the time domain using electro-optic sampling with a time resolution of approximately 5 picoseconds. With different orientations of the electro-optic crystal, we have measured different vector components of the electric field. The Fourier transform of the time-domain data yields the product of the beam impedance with the excitation spectrum of the bunch. Since the bunch length is known from streak camera measurements, the k loss factor is directly obtained. There is reasonably good agreement between the experimental k loss factor with calculations from the code MAFIA. To our knowledge, this is the first direct measurement of the k loss factor for bunch lengths shorter than one millimeter ( nns). We also present results of magnetic bunch compression (using a dipole chicane) of a high-charge photoinjector beam for two different UV laser pulse lengths on the pholocalhode. Al best compression, a 13.87 nC bunch was compressed to 0.66 mm (2.19 ps) rms, or a peak current of 3 kA. Other results from the photoinjeclor are given, and the laser system for pholocalhode excitation and electro-optic sampling is described.

Composite insulator degradation poses severe risks to power grid stability, rendering live detection of internal defects critically significant. The electric field detection method, as a non-contact solution, suffers from lack of field measurement data and unclear criteria for electric field-based degradation identification. To address this challenge, field samples of composite insulators with decayed and carbonized core rods are selected, and electric field distribution tests are conducted to capture the fundamental distortion characteristics induced by degradation. Subsequently, artificial simulation experiments are performed to investigate local electric field distortion characteristics under varying degradation severities, positions, detection distances and different installment configurations. Based on these findings, a four-array local electric field detection method and criteria are proposed and validated through testing on field-degraded insulators. The results indicate that the four-array detection method effectively identifies carbonization and decay defects in composite insulator core rods, with characteristic criteria being that the ratio of maximum to minimum electric field amplitudes Q<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> satisfies 1<Q<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub><1.4~1.6;the ratio of maximum electric field amplitude to the average of the other three probes Q<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> satisfies 1<Q<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub><1.3~1.5;and the electric field variation coefficient ΔE<10. These findings provide technical support for intelligent operation and maintenance of external insulation in power transmission and distribution systems.

Amplitude and phase-controlled mid-infrared field transients are generated by phase-matched difference frequency mixing of near-infrared pulses shaped using a liquid crystal modulator. The generated electric field transients are directly measured using ultrafast free-space electro-optic sampling.

Electro-optic sampling of surface space-charge fields on III–V compounds

In this study, oxidative stress and lipid peroxidation in honey bee larvae, pupae and the midguts of adult bees were investigated during a one-year exposure to radiofrequency electromagnetic fields (RF-EMFs) at a frequency of 900 MHz under field conditions. The experiment was carried out on honey bee colonies at three locations with electric field levels of 30 mV m-1, 70 mV m-1 and 1000 mV m-1. Antioxidant enzymes, glutathione-S-transferase (GST), catalase (CAT) and superoxide dismutase (SOD) and thiobarbituric acid reactive substances (TBARS) as indicators of lipid peroxidation were measured spectrophotometrically. The GST activity within the same developmental stage showed no significant differences regardless of electric field level or sampling time. The highest GST activity was found in the pupae, followed by activity in the larvae and midguts. Both CAT activity and TBARS concentration were the highest in the midguts, regardless of field level and sampling time. The larvae showed a significantly higher TBARS concentration at the location with an electric field level of 1000 mV m-1 compared to the locations with lower levels. Our results show that RF-EMFs at a frequency of 900 MHz can cause oxidative stress in honey bees, with the larval stage being more sensitive than the pupal stage, but there was no linear relationship between electric field level and effect in any of the developmental stages.

This letter presents a novel method for predicting the electromagnetic field radiated by an equipment under test (EUT) in free space. The method is based on the knowledge of the electric field values close to the metallic walls of a reverberation chamber where the device is placed. From these field samples, a set of equivalent sources is retrieved. The equivalent sources likewise produce in free space the same field radiated by the EUT.

In this article, a source reconstruction problem with four point sources is studied. The electric field data is used to reconstruct the sources. The field sampling is made with seven different sampling periods. Noise is added to the sampled field. The reconstructed field on the measurement surface and the reconstructed field with respect to distance are calculated to measure the performance of each sampling rate. In addition, the reconstructed currents are compared to the actual currents. The entries of the moments matrix are calculated with a semi-analytical procedure. This semi-analytical procedure has been recently reported by the author. The method of moments equation is solved using the least square QR method.