Probe Field Research Articles

Comparing field and lab quantitative stable isotope probing for nitrogen assimilation in soil microbes.

Soil microbes are responsible for critical biogeochemical processes in natural and agricultural ecosystems. Despite their importance, the functional traits of most soil organisms remain woefully under-characterized, limiting our ability to understand how microbial populations influence the transformation of elements such as nitrogen (N) in soil. Quantitative stable isotope probing (qSIP) is a powerful tool to measure the traits of individual taxa. This method has rarely been applied in the field or with 15N to measure nitrogen assimilation. In this study, we measured genus-specific microbial nitrogen assimilation in two agricultural soils and compared field and lab 15N qSIP methods. Our results identify taxa important for nitrogen assimilation in agricultural soils, shed light on the field relevance of lab qSIP studies, and provide guidance for the future application of qSIP to measure microbial traits in the field.

Electromagnetically induced transparency and second-order sideband Effects in a Laguerre-Gaussian cavity optorotational system with Kerr medium

Abstract In this paper, we investigate the phenomena of electromagnetically induced transparency (EIT) and the generation of second-order sideband in a Laguerre-Gaussian (LG) cavity optorotational sys tem with a Kerr nonlinear medium. Using the perturbation method, we analyze the first- and second order sideband generations in the output field from the system under the actions of a strong control
field and a weak probe field. Numerical simulations show that the Kerr nonlinearity can lead to the occurrence of the asymmetric line shape in the transmission of the probe field and the efficiency of second-order sideband generation, and the Kerr nonlinearity can enhance the efficiency of the second order sideband generation. Comparing with traditional scheme for generating the second-order sideband, our spectral shape of the second-order sideband is amplified and becomes asymmetric, which has potential applications in precision measurement, high-sensitivity devices, and frequency conversion.

Calculated Waveform and Peculiarity of Radiated Electric Field due to Collision ESD Between Metallic Spheres With Charging Voltages Below 1000 V Using Spark Resistance Law

ABSTRACTCollision ESD between charged metallic objects below 1000 V causes electromagnetic interference in electronic equipment and devices. This interference is being observed to intensify at lower charging voltages. The phenomenon was first identified by Masmitsu Honda, but its underlying mechanism remains unclear even today. Originally, the charging voltage and spark length of collision ESD are unknown due to measurement difficulties, making it extremely challenging to establish the relationship between the radiated electric field strength and the spark property in such cases. In this study, to clarify the above mentioned electromagnetic phenomenon in collision ESD, a method of calculating the radiated electric field along with a spark length estimated from the measurement strength of radiated field peak is presented using the spark resistance law developed by Rompe and Weizel. The validity is confirmed by our previous measurement data on radiated electric field due to the collision ESD between charged spherical electrodes with a diameter of 30 mm at charging voltages from 300 to 600 V, employing an optical field probe with a wideband up to 10 GHz. The estimated spark length is verified by comparing it with the spark lengths based on an empirical Paschen's formula between fixed electrodes and the discharge data from past literature on metal electrodes, revealing the peculiarity effect of the radiated electric field strength caused by “constant breakdown potential gradient” that occurs at charging voltages below 1000 V.

Plasma displacement calculation for TT-1 device based on multiple magnetic probes fitting methods

The HT-6M device has been upgraded and rebranded as the Thailand Tokamak 1 (TT-1), which has been reinstalled and is now operational in Thailand. In tokamak discharge experiments, precise monitoring of plasma position and the implementation of effective feedback control are essential for ensuring the stability of the high-temperature plasma. Accurate calculation of plasma displacement is critical to the success of the experiment. This paper presents a method for calculating plasma displacement through a multi-probe fitting technique, utilizing data from twelve magnetic field probes. Initially, magnetic field signals generated by the plasma are collected via multiple magnetic field probes installed poloidally outside the vacuum chamber, coupled with corresponding signal conditioning and integration circuits, with each probe undergoing calibration. Subsequently, during tokamak discharges, interference signals from the toroidal field coils, ohmic heating coils, and vertical field coils are generated by the magnetic system and corrected through a detailed calibration process. Lastly, the distances between the probes and the plasma are computed using data from the magnetic field probes, which are arranged in a circular configuration. The least squares method is employed to formulate a residual equation for fitting the actual plasma displacement. The effectiveness of this approach was validated through experimental data from the TT-1 device, demonstrating that the calculated plasma displacement exhibits a consistent trend with the CCD video recordings. This multi-probe displacement calculation method enables precise control of plasma displacement, thereby providing theoretical support for tokamak experiments and establishing a foundation for future experimental operations and data analysis.

High Interference-Resistant Magnetic Field Probe for Non-Invasive Current Distribution Monitoring in Press Pack IGBTs of HVDC Valves

High Interference-Resistant Magnetic Field Probe for Non-Invasive Current Distribution Monitoring in Press Pack IGBTs of HVDC Valves

Ultrahigh-resolution atomic localization via superposition of standing waves

In this study we theoretically demonstrate ultrahigh-resolution two-dimensional atomic localization within a three-level λ-type atomic medium via superposition of asymmetric and symmetric standing wave fields. Our analysis provides an understanding of the precise spatial localization of atomic positions at the atomic level, utilizing advanced theoretical approaches and principles of quantum mechanics. The dynamical behavior of a three-level atomic system is thoroughly analyzed using the density matrix formalism within the realm of quantum mechanics. A theoretical approach is constructed to describe the interaction between the system and external fields, specifically a control field and a probe field. The absorption spectrum of the probe field is thoroughly examined to clarify the spatial localization of the atom within the proposed configuration. A theoretical investigation found that symmetric and asymmetric superposition phenomena significantly influence the localized peaks within a two-dimensional spatial domain. Specifically, the emergence of one and two sharp localized peaks was observed within a one-wavelength domain. We observed notable influences of the intensity of the control field, probe field detuning and decay rates on atomic localization. Ultimately, we have achieved an unprecedented level of ultrahigh resolution and precision in localizing an atom within an area smaller than λ/35 × λ/35. These findings hold promise for potential applications in fields such as Bose–Einstein condensation, nanolithography, laser cooling, trapping of neutral atoms and the measurement of center-of-mass wave functions.

Dynamically controllable two-color electromagnetically induced grating via spatially modulated inelastic two-wave mixing

A scheme for controlling two-color electromagnetically induced grating (TCEIG) in a coherently prepared cold atomic ensemble with a four-level inverted Y-type configuration is proposed via exploiting inelastic two-wave mixing process. By adding an intensity mask behind the auxiliary control field, the transmission functions of the incident probe field and the generated signal field are modulated periodically, thereby leading to the formation of TCEIG. Using experimentally achievable parameters, both the probe and signal fields with different frequencies can be simultaneously diffracted into high-order diffractions. It is found that the diffraction efficiencies of TCEIG, especially the first-order diffraction efficiency, can be significantly improved via adjusting the detunings of the probe and signal fields. Furthermore, it is also demonstrated that the diffraction of TCEIG can be manipulated via tuning the intensity and detuning of the control field. Finally, we investigate the influence the phase mismatch on the diffraction of TCEIG. It is shown that the diffraction pattern of the probe field is rather robust against the phase mismatch, while the diffraction intensities of the signal field are suppressed by the phase mismatch. Our scheme may provide a possibility for the all-optical control of optical switch and wavelength division multiplexing.

Tunable bistability, optomechanical and magnomechanically induced transparency in opto-magnomechanical system

We investigate theoretically the optical properties of a hybrid optomechanical system embedded with a yttrium iron garnet (YIG) sphere. It is considered that YIG interacts with a single mode of the microcavity through magnetic dipole coupling. To enhance the magnomechanical coupling, the magnon mode is directly driven by a microwave field. The microcavity is driven by the control and probe field. The study of steady-state dynamics of the system shows bistable behavior. Furthermore, optomechanically induced transparency under the influence of a strong control field in the system is explored. In addition, magnomechanically induced transparency (MMIT) due to the presence of nonlinear magnon–phonon interaction is studied. Fano like shape is observed in MMIT. The impact of different system parameters is studied. Our results will provide a theoretical approach to understand opto-magnomechanical systems. These results may be useful in all optical switching devices and optical transistors.

Application of rare earth elements in dual-modality molecular probes.

The unique 4f subshell electronic structure of rare earth elements endows them with exceptional properties in electrical, magnetic, and optical domains. These properties include prolonged fluorescence lifetimes, large Stokes shifts, distinctive spectral bands, and strong resistance to photobleaching, making them ideal for the synthesis of molecular probes. Each imaging technique possesses unique advantages and specific applicabilities but also inherent limitations due to its operational principles. Dual-modality molecular probes effectively address these limitations, particularly in applications involving high-resolution Magnetic Resonance Imaging (MRI) such as MRI/OI, MRI/PET, MRI/CT, and MRI/US. This review summarizes the applications, advantages, challenges, and current research status of rare earth elements in these four dual imaging modalities, providing a theoretical basis for the future development and application of rare earth elements in the field of dual-modality molecular probes.

Large Kerr Nonlinearity and Slow Group Velocity of Weak Probe in Quantum Dot Nanostructures

Abstract This paper presents the dynamics of Kerr nonlinearity and the phenomenon of slow group velocity in a Quantum Dot (QD) system, using the mechanism of electromagnetically induced transparency (EIT). Employing a three-level QD setup and leveraging a ladder-type excitation approach, we analyse the interaction between a weak probe pulse and a strong control beam. By employing density matrix formalism, we derive the expressions for both linear and nonlinear optical susceptibilities, along with first-order linear dispersion terms. Our findings reveal that susceptibilities in the QD system, both linear and nonlinear, can be finely adjusted to desired probe frequencies through control parameter manipulation. Moreover, under the EIT regime, we observe the Kerr susceptibility on the order of 10−12 m2 V2 at a probe wavelength 1.359 μm. Additionally, the group velocity of the probe field experiences a remarkable slowdown by a factor of 103 compared to the speed of light in vacuum. Results obtained may have potential applications in fabricating nonlinear optical devices.

Electromagnetic properties of superconductive low-β 325 MHz half-wave resonators at low RF field

Abstract A niobium prototype and two test unjacketed 325 MHz coaxial half-wave cavities with β = 0.21 were designed, fabricated, and tested at low RF fields. Electromagnetic properties were investigated using a vector network analyzer in the frequency domain and an RF generator, directional couplers, and power detectors in the time domain (both continuous wave and pulse mode). We analyzed and compared the response of the low-beta cavity in both normal and superconducting states. We studied the relationship between the resonator parameters and coupling devices to optimize the design of the RF power coupler and field probe antenna, aiming to achieve accurate cavity characterization. We proposed a tunable power coupler design that allows for varying the coupling coefficient when operating in a vacuum at liquid helium temperature. The typical responses of the cavity in case of under-, critical-, and over-coupling conditions obtained within a single cool-down are presented and analyzed. We introduced a simplified method based on decay measurements with cavity port switching for effective cavity characterization at low RF amplitudes. This method aligns well with standard Q-factor measurement protocols and can expedite experimental investigations with small RF signals. The Q 0 ( E acc ) curve for half-wave resonators at ultra-low amplitudes is analyzed and discussed. Experiments with coaxial half-wave cavities showed an almost constant Q 0 at RF fields ranging from 1 × 10−4 MV m−1 to 1 × 10−1 MV m−1. Additionally, a significant increase in the quality factor was observed after 120 ∘C baking. The presented results are discussed in the context of potential low-field applications of superconductive cavities.

Emission dynamics and spectrum of a nanoshell-based plasmonic nanolaser spaser

Abstract We study theoretically the emission and lasing properties of a single nanoshell spaser nanoparticle with an active core and a plasmonic metal shell. Using time-dependent equations for the gain medium and metal, we calculate the lasing threshold through an instability analysis. Below threshold, the nanoshell acts as an optical amplifier when excited by an external probe field, while above threshold, it enters a regime of autonomous lasing. At the gain threshold, the lasing starts at one frequency, typically a plasmon resonance of the nanoparticle. With increasing gain, the emission then broadens to additional frequencies. This result contrasts with previous findings reporting only a single emission wavelength above threshold. We also compute the full spectrum and linewidth of the nanolaser, revealing strong frequency shifts and an asymmetrical lineshape. Finally, we demonstrate that the emission line can be tuned across the visible spectrum by modifying the aspect ratio of the nanoshell.

Symmetry invariants and classes of quasiparticles in magnetically ordered systems having weak spin-orbit coupling

Symmetry invariants of a group specify the classes of quasiparticles, namely the classes of projective irreducible co-representations in systems having that symmetry. More symmetry invariants exist in discrete point groups than the full rotation group O(3), leading to new quasiparticles restricted to lattices that do not have any counterpart in a vacuum. We focus on the fermionic quasiparticle excitations under “spin-space group” symmetries, applicable to materials where long-range magnetic order and itinerant electrons coexist. We provide a list of 218 classes of new quasiparticles that can only be realized in the spin-space groups. These quasiparticles have at least one of the following properties that are qualitatively distinct from those discovered in magnetic space group(MSG)s, and distinct from each other:(i) degree of degeneracy,(ii) dispersion as function of momentum, and(iii) rules of coupling to external probe fields. We rigorously prove this result as a theorem that directly relates these properties to the symmetry invariants, and then illustrate this theorem with a concrete example, by comparing three 12-fold fermions having different sets of symmetry invariants including one discovered in MSG. Our approach can be generalized to realize more quasiparticles whose little co-groups are beyond those considered in our work.

Coherent mid-infrared vortex generation at room temperature for manipulation of microparticles

We investigate the generation of mid-infrared (mid-IR) vortex beams carrying orbital angular momentum (OAM) through nonlinear processes in an inhomogeneously broadened 85Rb atomic ensemble. By employing a four-level atomic system featuring two strong control fields and a weak probe field, we generate a non-degenerate four-wave mixing signal at a wavelength of 5.23 µm. Applying the density-matrix formalism, we derive an analytical expression for the nonlinear atomic coherence which facilitates the transfer of vortex characteristics such as topological charge and intensity and phase profiles from the probe field to the mid-IR signal. Numerical solutions of Maxwell’s wave equation confirm the generation of mid-IR vortex beams with adjustable topological charges and beam widths at different spatial positions. This technique offers significant potential for applications in mid-IR communication, providing additional bandwidth and improved data transmission rates, as well as in fields such as microfluidics, biophysics, and nanotechnology, where OAM-carrying beams can manipulate microparticles with precision.

Perisaccadic perceptual mislocalization strength depends on the visual appearance of saccade targets.

We normally perceive a stable visual environment despite eye movements. To achieve such stability, visual processing integrates information across a given saccade, and laboratory hallmarks of such integration are robustly observed by presenting brief perisaccadic visual probes. In one classic phenomenon, probe locations are grossly mislocalized. This mislocalization is believed to depend, at least in part, on corollary discharge associated with saccade-related neuronal movement commands. However, we recently found that superior colliculus motor bursts, a known source of corollary discharge, can be different for different image appearances of the saccade target. Therefore, here we investigated whether perisaccadic mislocalization also depends on saccade target appearance. We asked human participants to generate saccades to either low (0.5 cycles/°) or high (5 cycles/°) spatial frequency gratings. We always placed a high-contrast target spot at grating center, to ensure matched saccades across image types. We presented a single, brief perisaccadic probe, which was high in contrast to avoid saccadic suppression, and the subjects pointed (via mouse cursor) at the seen probe location. We observed stronger perisaccadic mislocalization for low-spatial frequency saccade targets and for upper visual field probe locations. This was despite matched saccade metrics and kinematics across conditions, and it was also despite matched probe visibility for the different saccade target images (low vs. high spatial frequency). Assuming that perisaccadic visual mislocalization depends on corollary discharge, our results suggest that such discharge might relay more than just spatial saccade vectors to the visual system; saccade target visual features can also be transmitted.NEW & NOTEWORTHY Brief visual probes are grossly mislocalized when presented in the temporal vicinity of saccades. Although the mechanisms of such mislocalization are still under investigation, one component of them could derive from corollary discharge signals associated with saccade movement commands. Here, we were motivated by the observation that superior colliculus movement bursts, one source of corollary discharge, vary with saccade target image appearance. If so, then perisaccadic mislocalization should also do so, which we confirmed.

Laser-Assisted Field Evaporation of Chromia with Deep Ultraviolet Laser Light.

In this work, samples of chromia (Cr2O3) scale have been prepared for atom probe tomography and field evaporated with deep ultraviolet laser light (258 nm wavelength). The investigated range of laser energies spans more than three orders of magnitude between 0.03 and 90 pJ. Furthermore, the effects of detection rate and temperature were investigated. Simultaneous voltage and laser pulses were employed on additional needle specimens to reduce the standing voltage and minimize background noise during the measurement. Smooth evaporation with minimal mass spectrum peak tails was maintained over the whole range of measurement parameters. High laser energies result in significant underestimation of the oxygen content. Only laser energies below 1 pJ resulted in measured values near the expected oxygen content of 60 at%, the closest being about 58 at%.

Generation and enhancement of sum sideband in a magnon Kerr nonlinearity assisted optomechanical system

Abstract A theoretical scheme to enhance the sum sideband generation (SSG) via magnon Kerr nonlinearity assisted optomechanical system is proposed. In this scheme, the yttrium iron garnet sphere is placed within the cavity system and the frequency components are generated at the sum sideband through optomechanical nonlinear interaction and cavity-magnon linear coupling interaction. The results show that the efficiency of SSG can be enhanced by several orders of magnitude, and the gain in SSG efficiency also varies. The dependence of SSG on the system parameters, including the power of the control field, the frequency detuning of the probe fields and the coupling strengths between the optomechanical coupling and the cavity-magnon coupling is analyzed in detail. The change of SSG by varying the optomechanical coupling strength and cavity-magnon coupling strength is also investigated, and it is found that new matching conditions are generated. The enhanced SSG method may have potential application prospects in realizing the measurement of high-precision weak forces, quantum information processing and quantum-sensitive sensing.

Lineshape of Amplitude-Modulated Stimulated Raman Spectra.

The amplitude modulation of a pump field and the phase-sensitive detection of a pump-induced intensity change of a probe field encompass a common practice in nonlinear spectroscopies to enhance the detection sensitivity. A drawback of this approach arises when the modulation frequency is comparable to the width of the spectral feature of interest, since the presence of sidebands in the amplitude-modulated pump field provides distortion to the observed spectral lineshape. This represents a problem when accurate measurements of spectral lineshapes and line positions are pursued, as recently happened in our group with the metrology of the Q(1) line in the 1-0 band of molecular hydrogen. The measurement was performed with a Stimulated Raman Scattering spectrometer that was calibrated, for the first time, against an optical frequency comb. In this work, we develop an analytical tool for nonlinear Stimulated Raman spectroscopies that allows us to precisely quantify spectral distortions arising from high-frequency amplitude modulation in one of the interacting fields. Once they are known, spectral distortions can be deconvolved from the measured spectra to retrieve unbiased data. The application of this tool to the measured spectra is discussed.

The Faraday Rotation Measure of the M87 Jet at 3.5 mm with ALMA

Faraday rotation is an important probe of the magnetic fields and magnetized plasma around active galactic nuclei jets. We present a Faraday rotation measure (RM) image of the M87 jet between 85.2 and 101.3 GHz with a resolution of ∼2″ with the Atacama Large Millimeter/submillimeter Array. We found that the RM of the M87 core is (4.5 ± 0.4) × 104 rad m−2 with a low linear polarization fraction of (0.88 ± 0.08)%. The spatial RM gradient in the M87 jet spans a wide range from ∼ −2 × 104 rad m−2 to ∼3 × 104 rad m−2 with a typical uncertainty of 0.3 × 104 rad m−2. A comparison with previous RM measurements of the core suggests that the Faraday rotation of the core may originate very close to the supermassive black hole. Both an internal origin and an external screen with a rapidly varying emitting source could be possible. As for the jet, the RM gradient indicates a helical configuration of the magnetic field that persists up to the kiloparsec scale. Combined with the kiloparsec-scale RM measurements at lower frequencies, we found that RM is frequency-dependent in the jet. One possible scenario to explain this dependence is that the kiloparsec-scale jet has a trumpet-like shape, and the jet coil unwinds near its end.

Coherent control of dressing interaction of sequential-doubly-dressed four-wave mixing

Abstract We investigate the coherent control of dressing interaction in four-wave mixing (FWM) in a Y-type four-level atomic system based on the dressed states theory. We study the density matrix equation acted by two dressing fields simultaneously governing FWM signal intensity and the eigenvalues under the dressed state formalism. It is shown that the peak position and intensity of Autler–Townes splitting both originate from the dressing interaction as the detuning of the probe field is scanned. Moreover, it is observed that the interaction could be controlled by the dressing fields. Such flexibly controlled nonlinear signal has potential applications in optical communication and quantum information processing.