In this work, we present a comprehensive and comparative analysis of two detection modalities, i.e., polarization rotation and absorption measurement of light, for a double-resonance alignment magnetometer (DRAM). We derive algebraic expressions for magnetometry signals based on the description of multipole moments. Experiments are carried out using a room-temperature paraffin-coated cesium-vapor cell and measuring either the polarization rotation or absorption of the transmitted laser light. A detailed experimental analysis of the resonance spectra is performed to validate the theoretical findings for various input parameters. The results signify the use of a single isotropic relaxation rate, thus simplifying the data analysis for optimization of the DRAM. The sensitivity measurements are performed and reveal that the polarization-rotation detection mode yields larger signals and better sensitivity than absorption measurement of light.

The thermal lens effect has been well developed and exploited for decades. The type of thermal lens relies on the sign of the thermal-optical coefficient, where a negative coefficient material can only provide a concave lens and a positive coefficient material can only provide a convex lens. Here, we report an interesting thermal lens that can act as a cylindrical lens. When a radial or azimuthal vector beam illuminates on an absorbing and anisotropic light-transmitting medium, the refractive-index distributions depend on the anisotropic temperature gradient of the medium and, thus, can converge or diverge the probe beam in a single direction. We find that by changing the heating power of the vector beam, one can realize the cylindrical lenslike effect with an adjustable focal length. Our work holds promise for realizing the unidirectional modulation of the light field in an anisotropic light-transmitting medium with the thermal-optic effect and, thus, opens the door to utilizing the structured light beam to study the thermal-optical effect.

This work explores the excitation of a two-mode exciton-polariton condensate within a ring-shaped trap, with each mode manifesting as a distinct eigenstate characterized by oppositely directed azimuthal polariton currents. The coexistence of these condensate states is facilitated by a positive gain-loss balance for both states, sustained by external noncoherent laser pumping. We utilize interferometric methods to investigate these states. Spherical wave interferometry visualizes the azimuthal polariton currents and elucidates the spatial phase properties of the condensates. Plane-wave interferometry with a self-delayed replica of the condensate’s photoluminescence provides a highly sensitive approach for estimating the energy splitting between the states. The experimental observations are validated by numerical simulations. The study emphasizes the potential of these condensates to form the basis for flux polariton qubits, leveraging the superposition of current states within an annular optical trap.

We have modeled six abstracted detector designs, with the goal of determining their ability to resolve the direction to an antineutrino source, including two for which we have operational data for validating our computer modeling and analytical processes. We have found that the most promising options, regardless of scale and range, have angular resolutions on the order of a few degrees, which is better than any yet achieved in practice by a factor of at least two. We examine and compare several approaches to detector geometry for their ability not only to detect the inverse beta decay (IBD) reaction, but also to determine the source direction of incident antineutrinos. The information from these detectors provides insight into reactor power and burning profile, which is especially useful in constraining the clandestine production of weapons material. In a live deployment, a nonproliferation detector must be able to isolate the subject reactor, possibly from a field of much-larger power reactors; directional sensitivity can help greatly with this task. We also discuss implications for using such detectors in longer-distance observation of reactors, from a few kilometers to hundreds of kilometers.

Two-dimensional magnetism and valleys have recently emerged as two significant research areas, with intriguing properties and practical uses in advanced information technology. Considering the importance of these two areas and their coupling, the controllable creation of both magnetism and valley polarization is highly sought after. Based on first-principles calculations, we propose a class of two-dimensional monolayers with chemical formula ${\mathit{\text{MAZ}}}_3$, which is viewed as a $2H$-${\mathit{\text{MZ}}}_2$ trilayer passivated by an $A$-$Z$ bilayer on one side. Taking ${\text{VSiN}}_3$ as an example, the ${\mathit{\text{MAZ}}}_3$ monolayers are found to exhibit tunable magnetism and valleys. For the intrinsic ${\text{VSiN}}_3$ monolayer, it is a nonmagnetic semiconductor, with multiple degenerate valleys and trigonal warping near $K_{\pm }$ points in the band structure. Besides, the bands have spin splittings due to the spin-orbit coupling. Under a moderate carrier doping, the monolayer becomes a Stoner ferromagnet, which enhances the spin splittings of the valence band and generates valley splittings. Moreover, the Berry curvature is valley-contrasting, leading to distinct valley-spin-related anomalous Hall currents as the doping concentration increases. Our work opens up an avenue for modulating spin splittings and valley splittings via electric means, and provides opportunities for exploring advanced spintronic and valleytronic devices.

Electromagnetic wave polarization engineering with help from a pair of identical anisotropic metasurfaces of twisted optical axes, is introduced. Flawless linear polarization rotation and conversion to circular are demonstrated for lossless designs while symmetries between the responses of plasmonic and dielectric metasurfaces at different separating distances, are identified. The proposed concept expands the approach of twistronics in classical electrodynamics and reports optimal setups that can be directly utilized for polarization-controlled optical manipulation, holographic imaging, or angular-momentum multiplexing.

Silicon nitride (${\mathrm{Si}\mathrm{N}}_x$) is one of the most promising integrated photonics platforms, offering ultralow loss, significant Kerr nonlinearity, and extremely high integration capability. However, ${\mathrm{Si}\mathrm{N}}_x$ in the C band exhibits normal material group-velocity dispersion (GVD), while anomalous GVD, essential for most nonlinearity-based applications, can only be achieved in thick waveguides through geometric dispersion. The common challenge in the fabrication of thick waveguides without using the Damascene technique is the uniform filling of the gaps between closely located waveguides. To address this challenge, we elaborated a combined technological approach that includes plasma-enhanced chemical vapor deposition, reactive ion etching, and plasma-enhanced atomic-layer deposition. This approach reliably provides full and uniform filling of the complex etched profile gaps between 1-$\text{μ}\mathrm{m}$-thick silicon nitride waveguides, spaced at distances of the order of hundreds of nanometers. Additionally, using microring resonators, we experimentally demonstrated that voids within the upper cladding layer significantly affect the performance of the photonic integrated components.

The nanosized boron vacancy ($V_{\mathrm{B}}^{-}$) defect spot in hexagonal boron nitride (h-BN) is promising for a local magnetic field quantum sensor. One of its advantages is that a helium-ion microscope can make a spot at any location in an h-BN flake with nanometer accuracy. In this study, we investigate the properties of the created nanosized $V_{\mathrm{B}}^{-}$ defect spots by systematically varying three conditions: the helium-ion dose, the thickness of the h-BN flakes, and the substrate on which the h-BN flakes are attached. The physical background of the results obtained is successfully interpreted using Monte Carlo calculations. From the findings obtained here, a guideline for their optimal creation conditions is obtained to maximize its performance as a quantum sensor concerning sensitivity and localization.

Perovskite solar cells have emerged as a promising technology in the field of photovoltaics, owing to their notable advancements in power-conversion efficiency. Recent investigations have revealed a crucial dependency of efficiency on the source of bromide within the perovskite absorption layer. To elucidate the underlying nature of traps within these solar cells, a comprehensive series of measurements was conducted under varying light intensities. Subsequently, employing an electrodynamic theoretical model, the intrinsic processes inherent to caesium and lead-based perovskite solar cells with different bromide sources were analyzed. The study reveals significant differences in transient photocurrent measurements and photocurrent-voltage characteristics among perovskites originating from different bromide sources, measured under different light intensities. Leveraging theoretical analyses on the picosecond scale, the recombination mechanism of crystal defects was meticulously described revealing the pronounced influence of capture rates on electron-hole recombination dynamics. Furthermore, the investigation substantiated the presence of a band-bending phenomenon at the interface between the hole transport layer (HTL) and perovskite, elucidating the observed transient photocurrent phenomena. The findings significantly advance the understanding of the mechanisms underlying perovskite solar cells, offering valuable insights into their performance and paving the way for enhanced efficiency and stability in future device design and optimization.

Optically pumped atomic magnetometers are capable of measuring radio-frequency magnetic fields with high sensitivity, but their narrow bandwidth, of the order of 1 kHz, restricts their applications. Further, their full potential is often not realized, with noisy environments or quantum noise curtailing their sensitivity. This study presents a two-chamber atomic magnetometer, with independent control over the tuning field and pumping helicity in each chamber, which addresses both bandwidth and sensitivity limitations. It demonstrates a practical instance of bandwidth expansion, by simultaneous measurement of signals spaced more than 100 kHz apart, at frequencies corresponding to nuclear quadrupole resonance of ammonium nitrate and potassium chlorate, two materials commonly found in improvised explosive devices. It further demonstrates: the intrinsic reduction of common-mode noise, including environmental and probe light-shift noise, down to 2.4 $\mathrm{fT}/\sqrt{\mathrm{Hz}}$, with the use of resonant, but oppositely pumped, atomic chambers; the reduction of photon shot noise down to 28 $\mathrm{aT}/\sqrt{\mathrm{Hz}}$ with the use of 44 probe passes through the two chambers; and the reduction of atom noise down to 34 $\mathrm{aT}/\sqrt{\mathrm{Hz}}$, in agreement with prediction, using a large combined volume, 128 ${\mathrm{cm}}^3$, of ${}^{87}\mathrm{Rb}$ atoms. This work underlines the potential sensitivity of these quantum sensors, while exploring the technical limitation, namely the high pump power required, that stands as a barrier to that sensitivity. Further, it marks a significant step towards utilizing atomic magnetometers in applications demanding broader bandwidth or multiplexing, notably simultaneous measurements at far-spaced radio frequencies.

Precise control and utilizing the phase degree of freedom of spin waves is particularly crucial in developing unparalleled magnonic devices for unconventional computing. By exploring phases of coherent spin waves, we have achieved their constructive (destructive) interference, resulting in complete transmission (suppression) of spin-wave propagation in a wide frequency range. Furthermore, by applying a dc-gating current, we effectively switch types of the interference from constructive to destructive or vice versa at the same frequency, enabling the configurable realization of both xor and or logic functions in the same device. Our coherent spin-wave transistor gateable by a dc current represents a substantial step forward to the spin-wave logic devices or circuits for magnonic computing.

Reconfigurable metasurfaces are potent platforms to control the propagation properties of light dynamically. Among different reconfiguration mechanisms available at optical frequencies, using nonvolatile phase change materials is one of the most prominent. Tuning the refractive index of these materials, and thus changing the electromagnetic response of the device, can be achieved by external modulation that enables the transition between their amorphous and crystalline structural states. In this work, we study a structure that exploits these materials to fully control the electromagnetic response (i.e., electric, magnetic, and electromagnetic coupling). Powered by this controllability, we present how the metasurface can be designed to perform beam-steering and switchable one-way absorption applications. In addition, we demonstrate that the same platform can be designed to work in a nonlocal regime to implement a more efficient way of controlling light direction.

Converting quantum information from stationary qubits to traveling photons enables both fast qubit initialization and efficient generation of flying qubits for redistribution of quantum information. This conversion can be performed using cavity-sideband transitions. In the fluxonium, however, direct cavity-sideband transitions are forbidden due to parity symmetry. Here we circumvent this parity selection rule by using a three-wave mixing element to couple the fluxonium to a resonator. We experimentally demonstrate a scheme for interfacing the fluxonium with traveling photons through microwave-induced parametric conversion. We perform fast reset on the fluxonium qubit, initializing it with $>95\mathrm{\%}$ ground-state population. We then implement controlled release and temporal shaping of a flying photon, useful for quantum state transfer and remote entanglement. The simplicity and flexibility of our demonstrated scheme enables fluxonium-based remote entanglement architectures.

The Laser Interferometer Space Antenna (LISA) is a gravitational wave detector in space. It relies on a postprocessing technique named time-delay interferometry to suppress the overwhelming laser frequency noise by several orders of magnitude. This algorithm requires intersatellite-ranging monitors to provide information on spacecraft separations. To fulfill this requirement, we use on-ground observatories, optical sideband-sideband beatnotes, pseudorandom noise ranging (PRNR), and time-delay interferometric ranging (TDIR). This article reports on the experimental end-to-end demonstration of a hexagonal optical testbed used to extract absolute ranges via the optical sidebands, PRNR, and TDIR. These were applied for clock synchronization of optical beatnote signals sampled at independent phasemeters. We set up two possible PRNR processing schemes: Scheme 1 extracts pseudoranges from PRNR via a calibration relying on TDIR; Scheme 2 synchronizes all beatnote signals without TDIR calibration. The schemes rely on newly implemented monitors of local-PRNR biases. After the necessary PRNR treatments (unwrapping, ambiguity resolution, bias correction, in-band jitter reduction, and/or calibration), Schemes 1 and 2 achieved ranging accuracies of 2.0–8.1 cm and 5.8–41.1 cm, respectively, below the classical 1-m mark with margins.

Boron arsenide (BAs) has emerged as a strong contender for next-generation functional materials, boasting desirable attributes such as high thermal conductivity and ambipolar mobility. However, a critical yet underexplored challenge lies in understanding its heat conduction capabilities under inhomogeneous strain, which is pivotal across various functional devices and operational conditions. Here, through modeling thermal transport in bent BAs and $\mathrm{Si}$ nanoribbons, a striking difference is revealed. Namely, the BAs nanoribbons exhibit nearly twice the reduction in thermal conductivity compared with $\mathrm{Si}$ under identical bending conditions. This significant disparity is driven by two key factors: the pronounced effect of phonon-spectra broadening under strain and the inhomogeneous strain-induced narrowing of the acoustic and optical (ao) gap. Together, these factors relax the originally restricted phonon scattering phase space and fundamentally alter phonon scattering dynamics. Our findings not only offer a new perspective on how heat transfer can be dynamically modulated in BAs, but also provide crucial insights into enhancing thermal performance in BAs-based functional devices.

We investigate the effect of the magnetic field on a photonic crystal Josephson traveling-wave parametric amplifier (TWPA). We show that the observed change in the photonic band gap and plasma frequency of the TWPA can be modeled by considering the suppression of the critical current in the Josephson junctions (JJs) of the TWPA due to the Fraunhofer effect and closing of the superconducting gap. Accounting for the JJ geometry is crucial for understanding the field dependence. In one in-plane direction, the TWPA band gap can be shifted by 2 GHz using up to 60 mT of field, without losing gain or bandwidth, showing that TWPAs without superconducting quantum interference devices (SQUID) can be field tunable. In the other in-plane direction, the magnetic field is perpendicular to the larger side of the Josephson junctions, so the Fraunhofer effect has a smaller period. This larger side of the JJs is modulated to create the band gap. The field interacts more strongly with the larger junctions, and as a result, the TWPA band gap closes and reopens as the field increases, causing the TWPA to become severely compromised already at 2 mT. A slightly higher operating limit of 5 mT is found in the out-of-plane field, for which the TWPA’s response is hysteretic. These measurements reveal the requirements for magnetic shielding needed to use TWPAs in experiments where high fields at the sample are required. With magnetic shields and at a distance from a sample at the magnet center, we can operate the TWPA while applying over 2 T to the sample.

In this work we propose a method for probing the chirality of nanoscale electromagnetic near fields utilizing the properties of a coherent superposition of free-electron vortex states in electron microscopes. Electron beams optically modulated into vortices carry orbital angular momentum, thanks to which they are sensitive to the spatial phase distribution and topology of the investigated field. The sense of chirality of the studied specimen can be extracted from the spectra of the electron beam with nanoscale precision owing to the short picometer de Broglie wavelength of the electron beam. We present a detailed case study of the interaction of a coherent superposition of electron vortex states and the optical near field of a golden nanosphere illuminated by circularly polarized light as an example, and we examine the chirality sensitivity of electron vortex beams on intrinsically chiral plasmonic nanoantennae.

Gyroscopic metamaterials integrate rotational units within periodic structures, enabling precise manipulation of mechanical waves and exhibiting programmable material properties. This study delves into the polarization characteristics of one-dimensional (1D) chains and two-dimensional (2D) networks of gyroscopic metamaterials, highlighting the ability to modulate the dispersion band structure through rotational elements. By leveraging dynamic tunability, we effectively tune the band gaps for polarized waves across a broad frequency range. Through wave polarization, we discover a Faraday-like rotation effect in linearly polarized mechanical waves. By adjusting the input frequency or the spin speed, the manipulation of the polarization plane and the polarization state can be achieved, effectively replicating the phenomena of an optical model in a mechanical system. We confirm that 2D rectangular and triangular unit-cell gyroscopic metamaterials can serve as tunable filtering and tunable polarizing components, respectively. Additionally, we utilize circularly polarized waves to achieve selective excitation, enabling waves at the same frequency to exhibit diverse propagation patterns. Experimental validation in 1D systems confirms the capability of manipulating wave propagation through the generated polarization. Our research establishes a framework for exploring gyroscopic metamaterials’ capabilities in wave manipulation, fostering innovation in signal processing technologies.

This paper reports that ${\mathrm{Yb}}_2{\mathrm{O}}_3/{\mathrm{Mo}\mathrm{O}}_3$ stacks can be used effectively as a connecting electrode, enabling highly efficient tandem organic light-emitting diodes (OLEDs). The current efficiency of these tandem OLEDs more than doubles, from approximately 90 to 200 cd/A, compared to the single-layer devices. Additionally, this connecting electrode introduces little increase in the tandem OLED driving voltage, maintaining a value close to the sum of two single-layer devices. However, the energy-level alignments measured by ultraviolet photoemission spectroscopy show significant energy barriers in the ${\mathrm{Yb}}_2{\mathrm{O}}_3/{\mathrm{Mo}\mathrm{O}}_3$ stack. Analysis using photoemission measurements revealed the presence of gap states in the oxide stack and a high differential work function, 2.28 vs 6.38 eV on each side of the ${\mathrm{Yb}}_2{\mathrm{O}}_3/{\mathrm{Mo}\mathrm{O}}_3$ stack. Variable-temperature current-voltage measurements on ${\mathrm{Yb}}_2{\mathrm{O}}_3/{\mathrm{Mo}\mathrm{O}}_3$ stacks revealed that the gap states behave like Anderson-Mott localized quantum states, which form efficient hopping conduction paths for electrons and holes. These findings demonstrate that the gap states in electrodes can be effectively used to transport charges in tandem semiconductor devices.

Wavefront aberrations have significant impacts on the accuracy and long-term stability of cold-atom interferometers. This research presents an in situ method for directly measuring the phase shift induced by the wavefront of the Raman beam using the atom interferometer itself. To validate the feasibility of this approach, experiments involving the insertion of a glass plate with a known surface figure into the Raman beam path have been carried out. The phase introduced by the glass plate is measured experimentally by the atom interferometer and calculated theoretically based on the wavefront obtained from the wavefront sensor, and we find good agreement of the experimental results with the theoretical calculations. The method not only allows for the assessment of systematic errors in an atom interferometer, but also provides the capability to retroactively compute the wavefront of Raman beams based on the measured phase shift. The wavefront distribution of the glass plate is inversed from the phase measured by the atom interferometer. This inversed wavefront distribution is consistent with the surface of the glass plate measured by the wavefront sensor, which confirms the effectiveness of the method. This work provides a valuable approach to evaluate the systematic errors in atom interferometers that are sensitive to wavefront aberrations. Furthermore, it offers a novel method to measure the wavefront using atoms.