An introduction to the APL Special Issue on “Hybrid Quantum Devices” by the guest editors.

Artificial magnetic molecules can contribute to progressing toward large scale quantum computation by (a) integrating multiple quantum resources and (b) reducing the computational costs of some applications. Chemical design, guided by theoretical proposals, allows embedding nontrivial quantum functionalities in each molecular unit, which then acts as a microscopic quantum processor able to encode error

The search for an ideal single-photon source has generated significant interest in discovering emitters in materials as well as developing new manipulation techniques to gain better control over the emitters' properties. Quantum emitters in atomically thin two-dimensional (2D) materials have proven to be very attractive with high brightness, operation under ambient conditions, and the ability to be

In this Perspective Letter, we discuss the field of remote photonic bio-sensing and diagnosis while focusing on sensing involving spatial analysis of temporally varied defocused secondary speckle patterns. Collecting secondary speckle patterns that were back-reflected from an inspected tissue while properly defocusing the imaging lens allows us to measure nano-vibrations occurring in the tissue. The

A new generation of ultrafast and low-noise supercontinuum (SC) sources is currently emerging, driven by the constantly increasing demands of spectroscopy, advanced microscopy, and ultrafast photonics applications for highly stable broadband coherent light sources. In this Perspective, we review recent progress enabled by advances in nonlinear optical fiber design, detail our view on the largely untapped

In this work, we theoretically demonstrate that the ultimate detectivities in multi-stage interband cascade infrared photodetector configurations are higher than what can be achieved in a conventional single-absorber detector structure in any circumstance even including where carrier diffusion length is very long. Detailed derivations are provided to analytically show that in the limit of an infinite

The resonance properties of a plasmonic dipole antenna array depend on its geometry and the properties of its surrounding medium. The linear optical properties of an array of plasmonic dipole antennas can be modified with the inclusion of an epsilon-near-zero (ENZ) thin film. In this work, we numerically investigate the roles of the antenna dimensions, the ENZ film thickness and loss, and the separation

Metal nanostructures support plasmon oscillations on their surfaces, which normally decay very quickly. Nevertheless, the lifetime of these oscillations can be extended near a longer lifetime particle, e.g., a molecule. We utilize this phenomenon for ultrahigh (single-molecule) resolution ultrafast apertureless (scattering) applications. We demonstrate the phenomenon with the numerical solutions of

Nonreciprocal optical devices based on magneto-optical ferrites in their low-loss regimes have been widely investigated as a promising platform for integrated photonics. Nonreciprocity in such devices originates from circular birefringence, leading to frequency splitting of forward and backward modes and, as a result, nonreciprocal transmission. In this paper, we propose an alternative approach to

Accurate sizing of individual nanoparticles is crucial for the understanding of their physical and chemical properties and for their use in nanoscale devices. Optical sizing methods are non-invasive, rapid, and versatile. However, the low optical response of weakly absorbing subwavelength dielectric nanoparticles poses a fundamental challenge for their optical metrology. We demonstrate scalable optical

Light beams with helical wave fronts, also called optical vortices, have attracted great interest in the community of optics and photonics. They provide an additional degree of freedom for light manipulation, leading to wide-ranging potential applications in micro-particle trapping, optical microscopy, and even quantum information processing. Recently, metallic microstructures are introduced to confine

Terahertz quantum cascade structures using double longitudinal-optical phonon intrawell scattering for depopulation are theoretically studied. A density matrix Monte Carlo method is used to calculate the temperature dependent optical power, in double phonon structures with diagonal optical transitions. It is shown that using depopulation transitions greater than the resonant longitudinal-optical phonon

Multiresonant plasmonic nanoantennas can enhance nanolocalized multiphoton processes or enable wavelength-multiplexed nano-optic operations by supporting multiple spatially overlapped plasmonic modes. Nevertheless, current multiresonant plasmonic nanoantenna designs do not consider engineering multiresonant spectral responses with strict size and footprint constraints. Developing a strategy to engineer

We have studied the design, epitaxy, and performance characteristics of deep ultraviolet (UV) AlGaN light emitting diodes (LEDs). By combining the tunnel junction and polarization-engineered AlGaN electron blocking layer, a maximum external quantum efficiency and wall-plug efficiency of 0.35% and 0.21%, respectively, were measured for devices operating at ∼245 nm, which are over one order of magnitude

Back contact transparent conductive electrodes are essential components of semi-transparent perovskite solar cells, which are especially beneficial for tandem photovoltaics. In this Letter, we present a way to realize ultrathin metal layers in ITO-metal-ITO (IMI) electrode stacks, which are characterized by the superior infrared transmittance and electrical conductivity. The metal layers are deposited

The low work function material lithium fluoride (LiF) facilitates electron-selective contacts to n-type silicon and is frequently used in dopant-free heterocontacts for silicon solar cells. Our photoelectron spectroscopy (PES) data show that LiF deposition on n-Si leads, indeed, to Fermi-level crossing of the conduction band minimum. Furthermore, PES reveals intrinsic surface band bending on hydrogen-terminated

Twistronic assembly of 2D materials employs the twist angle between adjacent layers as a tuning parameter for designing the electronic and optical properties of van der Waals heterostructures. Here, we study how interlayer hybridization, weak ferroelectric charge transfer between layers, and a piezoelectric response to deformations set the valence and conduction band edges across the moiré supercell

Defect-induced nonradiative recombination limits power conversion efficiency (PCE) of organic–inorganic lead halide perovskite solar cells (PSCs). Recently, molecular passivation methods using ammonium salts and Lewis bases have been gathering tremendous attention for reducing defects at perovskite film surfaces. In this work, we find that an excess amount of 4-tert-butylpyridine (4-tBP), which is

Planar Hall effect (PHE) in topological insulators (TIs) is discussed as an effect that stems mostly from conduction due to topologically protected surface states. Although surface states play a critical role and are of utmost importance in TIs, our present study in Bi2Te3 thin films reflects the need for considering the bulk conduction in understanding the origin of PHE in TIs. This necessity emerges

A broad, bell-shaped intensity component is observed in low-energy electron diffraction from high-quality epitaxial 2D-systems. Three 2D-systems, graphene on Ir(111), graphene on SiC(0001), and hexagonal boron nitride on Ir(111), have been prepared in situ under ultra-high vacuum conditions. In all three systems—independent of substrate material—similar strong diffuse intensity is observed, exhibiting

The exceptional actuation properties of liquid crystal elastomers (LCEs) have made these materials highly attractive for various emerging applications such as soft robotics and artificial muscles. The large strain gradients occurring under thermal stimuli induce bending and curling of initially flat LCE films. Due to the complex physics behind the spontaneous deformation in nematic liquid crystal elastomers

The single Helmholtz resonator obtains only one absorption peak in the broad frequency range, which limits its application in reducing the noise with multiple spectra. This paper reports an acoustic multi-layer Helmholtz resonance metamaterial, which can achieve multiple absorption peaks at given low-frequency targets. Meanwhile, through adjusting structural parameters of the multi-layer Helmholtz

A low p–n built-in potential (1.75 V) makes 3C-SiC an attractive choice for medium voltage bipolar or charge balanced devices. Until recently, most 3C-SiC had been grown on Si, and power device fabrication had, therefore, been hindered by issues, such as high defect density and limited processing temperature, while devices were necessarily limited to lateral structures. In this work, we present the

The low-frequency noise is of special interest for carbon nanotubes devices, which are building blocks for a variety of sensors, including radio frequency and terahertz detectors. We studied noise in as-fabricated and aged carbon nanotube networks (CNNs) field-effect transistors. Contrary to the majority of previous publications, as-fabricated devices demonstrated the superposition of generation-recombination

Various approaches are being considered to address the demand for high-throughput (Gb/s) point-to-point wireless communication systems in 5G infrastructure and sub-THz transceivers. Two fully integrated CMOS wireless transmitters with frequency shift keying (FSK) modulation were prototyped in a standard 55 nm SiGe process. Benefiting from the coupled oscillator loop system, the single channel data

We report the effect of stress or strain on the electronic characteristics of a normally off AlGaN/GaN high electron mobility transistor (HEMT) and demonstrate its role as a highly sensitive pressure sensor. We observe that the HEMT drain current exhibits a linear change of 2.5%/bar upon the application of pressure, which is translated to a strain sensitivity of 1250 ppm−1. This is the highest strain

In this work, we demonstrate a high-performance ultraviolet phototransistor (UVPT) based on the AlGaN/GaN high-electron mobility transistor (HEMT) configuration. When the device is biased at off state, the peak photoresponsivity (R) of 3.6 × 107 A/W under 265 nm illumination and 1.0 × 106 A/W under 365 nm illumination can be obtained. Those two R values are one of the highest among the reported UVPTs

This paper presents a previously unreported mechanism for the formation of High Spatial Frequency Laser Induced Periodic Surface Structures (HSFL) in GaAs upon irradiation by femtosecond laser pulses (repetition rate = 1 kHz, τ = 150 fs, λ = 390 nm) that is driven by point defect diffusion, desorption of surface atoms, and roughening of the surface. The HSFL have trenches that are 100 nm deep, an average

Femtosecond pump-probe experiments in a transmission geometry were performed on Sn-doped n-type β-Ga2O3. With the pump and probe wavelengths below the bandgap, the differential transmission signal was determined by the free electron dynamics. Differential transmission decay times and their spectral dependence were used to evaluate electron-phonon scattering for polar optical (PO) and intervalley phonons

We observed an unusual double-shifted hysteresis loop in a perpendicular exchange-coupled Co/IrMn system at room temperature, which leads to an uneven exchange bias field in the positive and the negative field. With the thickness of the antiferromagnetic layer ranging from 4.8 to 10.4 nm, the negative exchange bias field is approximately 100 Oe larger than the positive exchange bias field. This result

In this Letter, we present experimental data that demonstrate a spin wave interference detection using an inverse spin Hall effect (ISHE). Two coherent spin waves are excited in a yttrium-iron garnet waveguide by continuous microwave signals. The initial phase difference between the spin waves is controlled by the external phase shifter. The ISHE voltage is detected at a distance of 2 and 4 mm away

We investigate the effect of curvature on the energy and stability of domain wall configurations in curved cylindrical nanotubes and nanowires. We use micromagnetic simulations to calculate the phase diagram for the transverse wall (TW) and vortex wall (VW) states in tubes, finding the lower energy configuration and the metastability region where both types of walls can exist. The introduction of curvature

Boron-doped diamond granular thin films are known to exhibit superconductivity with an optimal critical temperature of T c = 7.2   K. Here, we report the measured in-plane complex surface impedance of boron-doped diamond films in the microwave frequency range using a resonant technique. Experimentally measured inductance values are in good agreement with estimates obtained from the normal state sheet

We report on one- to three-dimensional characterization of the pyroelectric properties of aluminum scandium nitride. By means of the laser intensity modulation method, we reconstructed the in-depth distribution of the spontaneous polarization with sub-micrometer resolution. The reconstructed profiles of the spontaneous polarization indicate that the thermal diffusivity and its temperature-dependence

Artificial neural networks have gained intensive attention in recent years because of their potential in effectively reducing energy consumption and improving computation performance. Ferroelectric materials are considered to be promising candidates for artificial synapses because of their multiple and nonvolatile polarization states under external stimuli. Despite artificial ferroelectric synapses

Stress-induced structural phase transitions in multiferroic BiFeO3 thin films have attracted much attention for both fundamental research and promising applications in electronic devices. In this work, with the assistance of spherical aberration-corrected transmission electron microscopy, a tetragonal phase with the super large tetragonality (c/a ∼ 1.53) was found in the epitaxial BiFeO3 thin film

Molybdenum oxides have attracted much interest due to their unique electronic properties. Here, we report a convenient and efficient method to synthesize centimeter-scale single crystal of MoO3 ribbons through an atmospheric pressure physical vapor deposition approach. Optical microscopy, atomic force microscopy, high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction

Elastic, deformable electrodes have attracted substantial interest owing to their applicability in unconventional stretchable devices. In this study, we investigate the effect of tensile strain on the conductive properties of gold nanowire (AuNW) network electrodes with macroscale mesh structures (mesh-shaped AuNW network electrodes) and the mechanism by which the mesh structure affects its conductivity

We conducted the operando atomic force microscopy (AFM) of ionic liquid (IL)/rubrene single crystal interfaces under the operation of an electric double-layer (EDL)-gated field-effect transistor (FET). We developed a top-side-gated EDL-FET and performed the simultaneous measurement of device characteristics and frequency-modulation AFM in the IL droplet. The AFM images revealed microscopic and macroscopic

This Letter studies the reverse leakage and breakdown mechanisms of vertical GaN-on-Si Schottky barrier diodes (SBDs) with and without argon-implanted termination (ArIT). The electrical leakage characteristics in the vertical GaN-on-Si SBD without edge termination sequentially go through the thermionic field emission, variable range hopping (VRH), and trap-assisted tunneling conduction mechanisms as

We report thermoelectric and electrical transport properties of Bi1.8Sb0.2Te3-ySey by tuning y. In contrast to the reported p-type conductivity of the end compounds with y = 0 and 3, a dominant n-type conduction mechanism is observed for y = 1.5 from the Hall measurement. Intriguingly, the magneto-Seebeck consequence is enhanced up to ∼ 20 times for y = 1.5 compared to the end members. The reasonable

Using Kelvin probe force microscopy, we studied the contact-electrification (CE) induced charge density on the surfaces of organic–inorganic composite oxide films, such as Nb2O5, ZrO2, and HfO2 films, prepared by a sol–gel method and annealed at different temperatures. The results show that positive triboelectric charges on the film surface gradually turn into negative ones with the increase in the

Wide bandgap mixed halide perovskites ABX3, in which X can be I, Br, or Cl, are promising materials to form highly efficient optoelectronic devices, because the optical bandgap can be controlled over a wide range by variation of the halogen composition. However, significant nonradiative losses must be overcome to approach the efficiency limit of single-junction solar cells. Here, we present a high

The p-type properties of carbon nanotubes (CNTs) in organic thermoelectric devices need urgent improvement for large-scale, low-grade thermal energy applications. Here, we present a suitable approach to significantly enhance the power factor (PF) by increasing the electrical conductivity through the low-temperature calcination-induced pyrolysis of the insulating γ-cyclodextrin polymer (PγCyD), which

The thermodynamic limit of photovoltaic efficiency for a single-junction solar cell can be readily predicted using the bandgap of the active light absorbing material. Such an approach overlooks the energy loss due to non-radiative electron-hole processes. We propose a practical ab initio procedure to determine the maximum efficiency of a thin-film solar cell that takes into account both radiative and

Through a combined theoretical and experimental study, we have investigated the synthesis and performance characteristics of InGaN/Si double-junction photoelectrochemical (PEC) water splitting devices, which promise a theoretical solar-to-hydrogen conversion efficiency ∼30% under AM 1.5G one-sun illumination. The double-junction photocathodes consist of a p+-InGaN top light absorber and a Si bottom

Measuring and understanding the interfacial resistance between the electrode and electrolyte are critically important for fabricating high-performance thermoelectrochemical cells. Although the charge transfer resistance and other resistance, such as the mass transfer resistance, may measure via electrochemical impedance spectroscopy, the resolution of the charge transfer semicircle in the Cole–Cole

The observation of the Hong–Ou–Mandel (HOM)-type two-photon interference (TPI) has played an important role in the development of photonic quantum technologies. The time-resolved coincidence-detection technique has been effectively used to identify and characterize the TPI phenomena of long-coherence optical fields. Here, we report on the experimental demonstration of the TPI of two phase-randomized

An emission wavelength around 1550   nm (telecom C-band) is highly appealing for nonclassical light sources, among others, due to the absorption minimum in standard glass fibers. In particular, semiconductor quantum dots at this wavelength promise to provide the outstanding results achieved with this emitter type in the near-infrared spectral region. Here, we study resonance fluorescence from InAs/GaAs

Hexagonal boron nitride (h-BN), a prevalent insulating crystal for dielectric and encapsulation layers in two-dimensional (2D) nanoelectronics and a structural material in 2D nanoelectromechanical systems, has also rapidly emerged as a promising platform for quantum photonics with the recent discovery of optically active defect centers and associated spin states. Combined with measured emission characteristics

It was first suggested that terahertz imaging has the potential to detect skin cancer twenty years ago. Since then, THz instrumentation has improved significantly: real time broadband THz imaging is now possible and robust protocols for measuring living subjects have been developed. Here, we discuss the progress that has been made as well as highlight the remaining challenges for applying THz imaging

By exploring geometry-governed magnetic interactions, curvilinear magnetism offers a number of intriguing effects in curved magnetic wires and curved magnetic films. Recent advances in experimental techniques change the status of curvilinear magnetism, allowing the exploitation of 3D curved nanomagnets in emerging devices with numerous applications. Here, we provide our Perspective on the recent progress

We demonstrate optical coupling between a single tin-vacancy (SnV) center in diamond and a free-standing photonic crystal nanobeam cavity. The cavities are fabricated using quasi-isotropic etching and feature experimentally measured quality factors as high as ∼11 000. We investigate the dependence of a single SnV center's emission by controlling the cavity wavelength using a laser-induced gas desorption

A membrane external-cavity surface-emitting laser (MECSEL) with an InAs/InP quantum dot (QD) based gain region is demonstrated. The pumping scheme employs a 90° off-axis parabolic mirror to focus the diode laser pump beam to a nearly circular pump spot. With this pump arrangement, the QD MECSEL with SiC heat spreaders produced 320 mW output power at room temperature with direct emission in the near-infrared

We have demonstrated a vertical UV-C LED composed of the Ga-face n-contact electrodes using the circular shape holes on mesa. In order to understand the dependence of optical performance on the mesa hole density, we varied the number of holes. As the number of holes on mesa increased, both the light output power and the external quantum efficiency of vertical chips have enhanced while preserving the

In classical and quantum systems, order is of fundamental importance to many branches of science. Still, disorder is prevalent in our natural world. It manifests in various ways, and overcoming its limitations would open up exciting applications. In this work, we numerically show that disorder-induced Anderson localization can be mitigated and transmission systematically restored in random media through

We experimentally demonstrate the enhanced four-wave mixing (FWM) by harnessing the forward stimulated Brillouin scattering (FSBS) within a silicon-based cascaded racetrack microring resonator (MRR). The frequency spacing of the split resonant peaks is precisely designed to match the Brillouin frequency shift (BFS). The cooperative interaction of the FSBS resonance and cascaded MRR resonance achieves

Room temperature light emission from optically active defect centers in two-dimensional layered materials has attracted great interest in recent years owing to the critical applications in the field of quantum information technologies. Therefore, efficient generation, detection, characterization, and manipulation of spatially localized emission from the defect centers are of crucial importance. Here

This paper investigates the conditions for a perfect anomalous reflection through a modulated metasurface consisting of a metallic cladding printed over a grounded slab. Differently to what has been previously published, the problem is rigorously addressed by modeling the metallic cladding through an equivalent penetrable impedance and accounting for the grounded slab through the problem's Green's

Establishing a mechanistic understanding of dynamic fracture is critical for the design of efficient and safe structural materials. Transformation toughening describes the process by which a crystal structure change can reduce the crack-driving force. The understanding of the dynamic behavior of transformation-toughened materials is limited. To clarify the relationship between crystal structure transformations