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Optical Sensing of Broadband RF Magnetic Field Using a Micrometer-Sized Diamond
摘要： High-resolution ?eld imaging with minimized invasiveness is of growing interest with the development of radio frequency (RF) integrated circuits and planar antenna characterization. In this paper, we propose an optical broadband sensor with static offset magnetic ?eld using a diamond crystal that contains an ensemble of nitrogen-vacancy (NV) centers. The spatial resolution of micrometer scale is demonstrated by using a diamond crystal of this size. This technique is based on the modulation of ?uorescence emitting by NV center under green laser excitation, by an off-axis magnetic ?eld at radio frequencies. We demonstrate experimentally the detection of an RF magnetic ?eld, with minimum measurable amplitude on the order of 0.1 Gauss, which is limited by the noise ?oor of the avalanche photodetector. The sensitivity can be further improved by noise suppression in optics. The bandwidth of the sensor is measured to be 15 MHz.
关键词： near-?eld imaging,magnetic ?eld,magnetic resonance,Instrumentation and measurement,real time,laser
更新于2025-09-23 15:23:52
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Effects of external magnetic field on the micro-structure of diamond-like carbon film prepared by pulsed laser deposition
摘要： The DLC ?lm was deposited by pulsed laser deposition in an external magnetic ?eld, and its optical property, surface morphology and atomic bonds were researched. The simulated ?ight tracks of the carbon ions in the magnetic ?eld showed that a number of the carbon ions were constrained by the Lorentz force, ?ing onto the substrate and forming the DLC ?lm. The contrast between the micro-structures of the DLC ?lms deposited in or out the magnetic ?eld showed that the external magnetic ?eld changed the expansion of the laser-produced plume and con?ned the surface diffusion of the charged particles on the substrate, improving the content of the sp3 bonds in the DLC ?lm.
关键词： pulsed laser deposition,diamond-like carbon ?lm,external magnetic ?eld,optical property,atomic bond
更新于2025-09-23 15:19:57
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[IEEE 2019 Compound Semiconductor Week (CSW) - Nara, Japan (2019.5.19-2019.5.23)] 2019 Compound Semiconductor Week (CSW) - Study on epitaxial lift-off of stacked GaAs solar cells for low-cost photovoltaic application
摘要： This paper presents a new methodology to determine the position of a magnetically guided robot (MGR) in horizontal planes using magnetic ?ux sensors. This position determination methodology can be used independently as well as in collaboration with optical sensors in the case of the optical blockage. A combination of linear Hall-effect sensors (two sensors for each axis of motion) was employed to measure the magnetic ?ux in the MGR’s working space. A con?guration of several electromagnets was used as a source of magnetic ?eld, and an analytical model of the system is developed. The MGR’s position was determined based on the polynomial relation between the Hall-effect sensors’ output and the location of the minimum magnetic potential energy point in horizontal planes. Using the cross-validation method, it was found that a fourth-order polynomial model could accurately predict the MGR’s position. Experiments were conducted on a horizontal plane to validate the performance of position estimation using the magnetic ?ux sensing method. The accuracy of the position determination method was 0.4-mm root-mean-square errors in both the x- and y-direction over 8 × 8 mm2 working area. This paper also experimentally validates a combined optical-magnetic position determination technique for the motion control of a magnetically guided robot in optical blockage conditions as unknown environment that can be used as a promising replacement of X-ray and ultrasound techniques.
关键词： switch control,Dual-axial motion,magnetic ?eld analysis,hall-effect sensor,magnetic levitation
更新于2025-09-19 17:13:59
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Laser-Tuned Large Photo Hall Effect in p-Type Silicon Based on Surface States
摘要： The photo Hall e?ect (PHE) has attracted much attention for a long time due to its broader application in photosensitive semiconductor devices. In this paper, we show a PHE observed in p-type silicon induced by pointolite irradiation, which di?ers from the conventional PHE caused by a surface light source. The Hall voltage is improved by 63 times when a laser is applied at the edge of the sample, and it presents good position-sensitive properties when the laser spot moves along the middle line of the sample. An ultra-broadband spectral responsivity is observed from 405 to 980 nm at 150?300 K. The experimental result shows that the laser-induced photo Hall voltage is not the simple superposition of photo current and dark current. Interestingly, this PHE can be greatly deteriorated when the surface state is destroyed and partially replaced by a Schottky barrier via covering with a thin Ag nano?lm. We attribute this phenomenon to the surface band bending caused by charged surface states. Compared with the traditional PHE, this laser-induced, position-sensitive, large-tuned-range e?ect based on surface states provides a di?erent approach to reveal the transmission properties of local unevenly distributed non-balanced carriers and can be used to design light-sensitive Hall devices.
关键词： photo Hall e?ect,surface states,recombination rate,magnetic ?eld,Schottky barrier
更新于2025-09-19 17:13:59
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Energy gain by laser-accelerated electrons in a strong magnetic field
摘要： This paper deals with electron acceleration by a laser pulse in a plasma with a static uniform magnetic ?eld B?. The laser pulse propagates perpendicular to the magnetic ?eld lines with the polarization chosen such that (Elaser · B?) = 0. The focus of the work is on the electrons with an appreciable initial transverse momentum that are unable to gain signi?cant energy from the laser in the absence of the magnetic ?eld due to strong dephasing. It is shown that the magnetic ?eld can initiate an energy increase by rotating such an electron, so that its momentum becomes directed forward. The energy gain continues well beyond this turning point where the dephasing drops to a very small value. In contrast to the case of purely vacuum acceleration, the electron experiences a rapid energy increases with the analytically derived maximum energy gain dependent on the strength of the magnetic ?eld and the phase velocity of the wave. The energy enhancement by the magnetic ?eld can be useful at high laser amplitudes, a0 (cid:3) 1, where the acceleration similar to that in the vacuum is unable to produce energetic electrons over just tens of microns. A strong magnetic ?eld helps leverage an increase in a0 without a signi?cant increase in the interaction length.
关键词： plasma,laser pulse,dephasing,magnetic ?eld,electron acceleration
更新于2025-09-19 17:13:59
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Atoma??photon entanglement near a plasmonic nanostructure
摘要： We investigate the atom–photon entanglement between a four-level double V-type quantum system and a linearly polarized ?eld near a plasmonic nanostructure in the presence of a static magnetic ?eld. It is demonstrated that the magneto-optical effect can affect the atom–photon entanglement only when the atom is near the plasmonic nanostructure. We show that atom–photon entanglement increases when the quantum system is placed near the plasmonic nanostructure in order to modi?cation of the spontaneous decays of the quantum system. It is demonstrated that the degree of entanglement (DEM) increases by increasing the intensity of the linearly polarized ?eld when the quantum system is close to the surface of the plasmons. Moreover, we ?nd that near the plasmonic nanostructure, the static magnetic ?eld has a major role in increasing the steady-state DEM so that the DEM is completely demolished in the absence of the static magnetic ?eld. Finally, it is shown that the atom–photon entanglement near a plasmonic nanostructure is destroyed by free space decay rate.
关键词： degree of entanglement,static magnetic ?eld,atom–photon entanglement,plasmonic nanostructure,spontaneous emission
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 4th International Future Energy Electronics Conference (IFEEC) - Singapore, Singapore (2019.11.25-2019.11.28)] 2019 IEEE 4th International Future Energy Electronics Conference (IFEEC) - Solar Photovoltaics Based Modified Power Quality Conditioner
摘要： This paper presents a new methodology to determine the position of a magnetically guided robot (MGR) in horizontal planes using magnetic ?ux sensors. This position determination methodology can be used independently as well as in collaboration with optical sensors in the case of the optical blockage. A combination of linear Hall-effect sensors (two sensors for each axis of motion) was employed to measure the magnetic ?ux in the MGR’s working space. A con?guration of several electromagnets was used as a source of magnetic ?eld, and an analytical model of the system is developed. The MGR’s position was determined based on the polynomial relation between the Hall-effect sensors’ output and the location of the minimum magnetic potential energy point in horizontal planes. Using the cross-validation method, it was found that a fourth-order polynomial model could accurately predict the MGR’s position. Experiments were conducted on a horizontal plane to validate the performance of position estimation using the magnetic ?ux sensing method. The accuracy of the position determination method was 0.4-mm root-mean-square errors in both the x- and y-direction over 8 × 8 mm2 working area. This paper also experimentally validates a combined optical-magnetic position determination technique for the motion control of a magnetically guided robot in optical blockage conditions as unknown environment that can be used as a promising replacement of X-ray and ultrasound techniques.
关键词： magnetic ?eld analysis,switch control,magnetic levitation,Dual-axial motion,hall-effect sensor
更新于2025-09-16 10:30:52
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Holographic interferences in strong-field ionization beyond the dipole approximation: The influence of the peak and focal-volume-averaged laser intensities
摘要： In strong-?eld ionization, interferences between electron trajectories create a variety of interference structures in the ?nal momentum distributions. Among them, the interferences between electron pathways that are driven directly to the detector and those that rescatter signi?cantly with the parent ion lead to holography-type interference patterns that have received great attention in recent years. In this work, we study the in?uence of the laser magnetic-?eld component onto the holographic interference pattern, an effect beyond the electric-dipole approximation, in experiment and theory. The experimentally observed nondipole signatures are analyzed via quantum trajectory Monte Carlo simulations. We provide explanations for the experimentally demonstrated asymmetry in the holographic interference pattern and its nonuniform photoelectron energy dependence as well as for the variation of the topology of the holography-type interference pattern along the laser-?eld direction. Analytical scaling laws of the interference features are derived, and their direct relation to either the focal-volume-averaged laser intensities, or to the peak intensities are identi?ed. The latter, in particular, provides direct access to the peak intensity in the focal volume.
关键词： laser magnetic-?eld,nondipole effects,strong-?eld ionization,quantum trajectory Monte Carlo simulations,holographic interference
更新于2025-09-12 10:27:22
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Generation of Low-Frequency Radiation Under the Laser Pulse Effect on a Plasma in a Magnetic Field
摘要： We reveal the possibility of a low-frequency radiation generation at a normal incidence of the laser pulse on a dense plasma in a constant magnetic ?eld. The generation occurs due to the motion of electrons under the magnetic ?eld e?ect and a ponderomotive force slowly varying with time localized in the skin layer where the laser radiation penetrates. The characteristic radiation frequencies are determined by the inverse duration of the laser pulse. We ?nd the ?eld strength of the radiation generated and its dependences on the Larmor frequency of electrons and the plasma and laser pulse parameters.
关键词： magnetic ?eld,terahertz radiation,ponderomotive force,femtosecond pulse,nonlinear current
更新于2025-09-12 10:27:22
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External Field-Controlled Ablation: Magnetic Field
摘要： The femtosecond laser ablation of silicon amidst an externally applied magnetic ?eld in different orientations was investigated with respect to the scanning direction and polarisation of the laser beam, by observation of ablation patterns and debris displacement in a range of ?uences, magnetic ?elds strengths, and geometries. Ultra-short ～ 230 fs laser pulses of 1030 nm wavelengths were utilised in the single and multi-pulse irradiation modes. Ablation with an externally applied magnetic B-?eld Bext ≈ 0.15 T was shown to strongly affect debris formation and deposition. The mechanism of surface plasmon polariton (SPP) wave can explain the ablated periodic patterns observed with alignment along the magnetic ?eld lines. The application potential of external ?eld controlled ablation is discussed.
关键词： magnetic ?eld,ablation,femtosecond laser fabrication
更新于2025-09-11 14:15:04