Small Linewidth Research Articles

A sequence of Type Ib, IIb, II-L, and II-P supernovae from binary-star progenitors with varying initial separations

Over the last decade, evidence has accumulated that massive stars do not typically evolve in isolation but instead follow a tumultuous journey with a companion star on their way to core collapse. While Roche-lobe overflow appears instrumental for the production of a large fraction of Type Ib and Ic supernovae (SNe), variations in the initial orbital period, $P_ init $, of massive interacting binaries may also produce a wide diversity of case B, BC, or C systems, with pre-SN stars endowed from minute to massive H-rich envelopes. Focusing here on the explosion of the primary donor star, originally 12.6\ we used radiation hydrodynamics and nonlocal thermodynamic equilibrium time-dependent radiative transfer to document the gas and radiation properties of such SNe, covering Types Ib, IIb, II-L, and II-P. Variations in init $ are the root cause of the wide diversity of our SN light curves, which present single-peak, double-peak, fast-declining, or plateau-like morphologies in the $V$ band. The different ejecta structures, expansion rates, and relative abundances (e.g., H, He, and can lead to a great deal of diversity in terms of spectral line shapes (absorption versus emission strength and width) and evolution. We emphasize that Halpha is a key tracer of these modulations, and that He is an enduring optical diagnostic for the presence of He. Our grid of simulations fares well against representative Type Ib, IIb, and II-P SNe, but interaction with circumstellar material, which is ignored in this work, is likely at the origin of the tension between our Type II-L SN models and observations (e.g., of SN\,2006Y). Remaining discrepancies in the rise time to bolometric maximum of our models call for a proper account of both small-scale and large-scale structures in core-collapse SN ejecta. Discrepant Type II-P SN models, with a high plateau brightness but small spectral line widths, can be fixed by adopting more compact red-supergiant star progenitors.

Ultrabroadband vernier cascaded microring filters based on dispersive Si3N4 waveguides

A viable candidate for use in silicon photonics and microwave photonics is the hybrid external cavity laser (ECL) chip, which offers a high extinction ratio, ultrabroadband mode-hopping-free tuning range, and small linewidth. It requires a photonic filter device with an ultrabroadband operating bandwidth and adjustable frequency selection capability. The Vernier cascaded microring filter is a prevailing filter technique that usually ignores chromatic dispersion and will result in noticeable frequency variations, particularly over a large frequency range. Based on dispersive Si3N4 waveguides, we develop ultrabroadband Vernier cascaded microring filters and examine the impact of chromatic dispersion. For the same waveguide geometry, the filter’s effective free spectral range (FSR) varies by more than 400 GHz with and without the dispersion. Furthermore, these Vernier filters, which are made of anomalous and normal dispersive waveguides respectively, exhibit mode hopping at the opposite frequency side. It leads to a sudden mode number leap and, consequently, a diversified dispersion condition for the convoluted filtering frequency. We show that this phenomenon is caused by the interplay between half of the FSR difference, and the accumulated frequency difference caused by the chromatic dispersion. Finally, the use of thermal-optical tuning enables accurate frequency tuning. Our findings offer a valuable resource for the engineering of hybrid ECLs at the chip scale.

A Low-mass line-rich Core Found in Massive Star-forming Region IRAS 16351-4722

We present Atacama Large Millimeter/submillimeter Array subarcsecond-resolution observations of both continuum and molecular lines at 345 GHz toward the massive star-forming region IRAS 16351-4722 (hereafter I16351). A total of 12 dust cores were detected based on high-spatial-resolution observations of the continuum. Among them, a high-mass core (11.6 M ⊙) and a low-mass core (1.7 M ⊙) show abundant molecular line emissions. 164 molecular transitions from 29 species and 104 molecular transitions from 25 species are identified in the high-mass and low-mass cores, respectively. Complex organic molecules (COMs) such as CH3OH, CH3OCHO, CH3OCH3, C2H5OH, and C2H5CN are detected in the two cores. Under the assumption of local thermodynamic equilibrium, the rotational temperatures and column densities of the COMs are derived with the XCLASS software. The maximum rotation temperature values in the low-mass core and the high-mass core were found to be approximately 130 K and 198 K, respectively. Additionally, the line widths in the high-mass core are larger than those in the low-mass one. The abundant COM line transitions, high gas temperatures, and smaller line widths indicate the presence of a low-mass line-rich core in the massive star formation region for the first time, while the high-mass line-rich core shows hot core properties. When comparing the molecular abundances of CH3OH, CH3OCHO, CH3OCH3, and C2H5OH of the two cores with other hot cores and hot corinos reported in the literature, we further confirm that both a hot core and a low-mass line-rich core are simultaneously detected in I16351.

Latest Advances in Perovskite LED Research

In recent years, there is a growing need for a better performance, lower cost, brighter and longer life luminous and display technology. Perovskite materials have attracted widespread attention because of their excellent performance in optoelectronic devices. For example, it has high carrier mobility, small emission line width, bandgap tunability, and strong photoluminescence quantum yield (PLQY). As a result, perovskite light-emitting diodes (LEDs) have developed rapidly over the past few years. This article starts with the basic parameters of perovskite LED (PeLED) devices and describes the basic structure and working principle of perovskite LED devices. And it mainly reviews the development history of 3D perovskite LEDs and states the latest progress in the research of perovskite quantum dots (QDs) and hole transport layers (HTLs) and electron transport layers (ETLs) in perovskite LED devices. Finally, the problems restricting the development of perovskite LEDs are summarized. This article offers a comprehensive understanding of perovskite LED devices and their future research directions.

High Peak Power Ultrashort Pulsed Passively Q-Switched Mode-Locked Bragg Laser Diode

We demonstrate a Bragg waveguide laser diode with an unbiased saturable absorber exhibiting passive Q-switched mode-locking with two AlInGaAs quantum wells. The widths of the observed passively mode-locked pulses ranged from 250 fs to 1640 fs under a Q-switching envelope. The frequency response showed the fundamental peak and smallest linewidths, for Q-switched operation, to range from 0.35 GHz to 1.15 GHz and 1.4 MHz to 9.1 MHz respectively. At 25 °C the devices demonstrated the highest peak power of ~10.1 W @ ~791 nm and highest peak to average power ratio of ~2800.

Density functional theory study on reaction mechanisms of Co(tbu2DAD)2 for area selective-atomic layer deposition of Co films on metal surfaces

As electronic devices scale in size approaching nm scales, the smaller feature sizes become more difficult and expensive to pattern. The most common patterning technique currently used in microelectronics industry, ArF laser immersion lithography, requires more and more steps to pattern one layer, the smaller the pitch becomes. Area selective-atomic layer deposition (AS-ALD) is one possible solution that allows for both fewer patterning steps and smaller feature sizes. However, the fundamental mechanisms of surface selectivity and the role of reducers in ALD growth are not fully understood. This modeling work focuses on the detailed atomic scale processes of AS-ALD deposition of Co metal on various substrate surfaces. Co is of particular interest for its capability in reducing resistance of metal interconnects in back end of lines when replacing Cu lines below 16 nm in critical dimension, and such a small linewidth can be achieved by the AS-ALD growth of Co films. This work shows the mechanisms and properties associated with the growth of Co on various surfaces (Cu, Pt, Co, and SiO2) as well as the role of a reducing agent in facilitating surface reactions during ALD processes. Density functional theory was used to describe the reaction mechanisms and accurately describe the system’s energetic and electronic characteristics during the deposition process. These findings provide insight into the fundamental mechanisms of selective ALD growth on metal surfaces against oxide surfaces and the catalytic role of reducers in facilitating the kinetics of ALD precursor reactions on metal surfaces.

External Filtered Modes of a Quantum Dot Laser Under the Influence of Double-Filtered Optical Feedback

When semiconductor lasers SLs are exposed to filtered optical feedback (FOB), they behave in two different ways. Under weak or strong feedback, the first is a singularly stable longitudinal mode with a small linewidth. The second is the so-called coherence breakdown condition, which also includes low frequency fluctuations (LFF) and chaotic oscillations. The latter has received a lot of attention recently due to the possible uses of chaotic lasers in chaotic lidar, covert communications, and chaotic correlation time-domain optical reflectometers, while the former has received a lot of research in recent years. We investigate the behavior of a quantum dot (QD) semiconductor laser subject to FOF from two separate external cavities both, numerically and experimentally. Our findings show that the second FOF allows for rich adjustment of the laser frequency. Our analysis of double-filtered optical feedback (DFOF) lasers is on fundamental solutions, sometimes referred to as continuous waves (CW) or external filtering modes (EFM), which result in a QD laser output with constant amplitude and frequency. The time delay suppression is dependent on the spectral width of the filter and how far it is from the solitary laser frequency, according to numerical calculations.

Metallo-Dielectric Millimeter-Wave Huygens’ Quarter-Wave and Half-Wave Plates

A novel metallo-dielectric Huygens’ unit cell is proposed that can be designed to operate either as a quarter-wave plate (QWP) or as a half-wave plate (HWP). The unit cell is based on a single-layer perforated dielectric, with straight (non-metallized) and 45° (metallized) elliptical holes. The novelty of the unit cell is its suitability for millimeter-wave implementation in printed-circuit board (PCB) fabrication due to the absence of metallic patterns of small line widths and gaps. As an example of their applicability, the wave plates are demonstrated in the near-field of 60-GHz band diffusion-bonded slot array antennas. The unit cell operating as a QWP is demonstrated in full-wave simulations and experimentally for linear-to-circular polarization conversion, whereby the combination of a linearly-polarized (LP) antenna and the QWP produces a circularly-polarized (CP) wave. Measurement results of the antenna and the QWP show ≤ -10-dB reflection from 59 to 63 GHz (6.6%), ≤ 3-dB axial ratio from 59.5 to 61.5 GHz (3.3%), and an overall efficiency ≥ 77% from 59.5 to 61.5 GHz. The unit cell operating as a HWP is demonstrated in full-wave simulations for polarization rotation of the LP antenna, and for changing the sense of rotation of a right-hand CP antenna into left-hand circular polarization.

Aluminum doping hexagonal barium ferrite films with large perpendicular magnetic anisotropy and high remanence ratio

Aluminum doping hexagonal barium ferrite film with large perpendicular magnetic anisotropy (PMA) and high remanence ratio was prepared on Al2O3 substrate by post-annealing at high temperature. The crystal structure measurements have shown that the crystallinity and degree of orientation were improved by post-annealing at high temperature, while it happened the Al ions diffusion from the Al2O3 substrate into the ferrite film at 1100 °C of annealing temperature. The diffusion phenomenon is also confirmed by the distribution of elements in the cross-section which displays a wide and slow-changing region of Al element. The Al element diffusion gives rise to a decrease of saturation magnetization, and an increase of coercivity and remanence ratio. Generally, a hexagonal barium ferrite film with large PMA field (HA = 18.1 kOe), relatively small FMR linewidth (540 Oe) and high remanence ratio (86%) was obtained by annealing the film at 1100 °C, which shows potential applied in self-biased microwave devices.

Improving Josephson junction reproducibility for superconducting quantum circuits: junction area fluctuation

Josephson superconducting qubits and parametric amplifiers are prominent examples of superconducting quantum circuits that have shown rapid progress in recent years. As such devices become more complex, the requirements for reproducibility of their electrical properties across a chip are being tightened. Critical current of the Josephson junction Ic is the essential electrical parameter in a chip. So, its variation is to be minimized. According to the Ambegaokar–Baratoff formula, critical current is related to normal-state resistance, which can be measured at room temperature. In this study, we focused on the dominant source of non-uniformity for the Josephson junction critical current–junction area variation. We optimized Josephson junction fabrication process and demonstrated resistance variation of 9.8–4.4% and 4.8–2.3% across 22 × 22 mm2 and 5 × 10 mm2 chip areas, respectively. For a wide range of junction areas from 0.008 to 0.12 μm2, we ensure a small linewidth standard deviation of 4 nm measured over 4500 junctions with linear dimensions from 80 to 680 nm. We found that the dominate source of junction area variation limiting {mathrm{I}}_{mathrm{c}} reproducibility is the imperfection of the evaporation system. The developed fabrication process was tested on superconducting highly coherent transmon qubits (T1 > 100 μs) and a nonlinear asymmetric inductive element parametric amplifier.

High-Q guided-mode resonance of a crossed grating with near-flat dispersion

Guided-mode resonances in diffraction gratings are manifested as peaks (dips) in reflection (transmission) spectra. Resonances with smaller line widths, i.e., with higher Q-factors, ensure stronger light–matter interactions and are beneficial for field-dependent physical processes. However, these high-Q resonances often suffer from strong angular and spectral dispersions. We demonstrate that a class of resonant modes with extraordinarily weak dispersion and Q-factor ∼1000 can be excited in crossed gratings simultaneously with the modes with well-known linear dispersion. Furthermore, the polarization of the incoming light can be adjusted to engineer the dispersion of these modes, and strong to near-flat dispersion or vice versa can be achieved by switching between two mutually orthogonal linear polarization states. We introduce a semi-analytical model to explain the underlying physics behind these observations and perform full-wave numerical simulations and experiments to support our theoretical conjecture. The results presented here will benefit all applications that rely on resonances in free-space-coupled geometries.

Deep Learning Methodology for Obtaining Ultraclean Pure Shift Proton Nuclear Magnetic Resonance Spectra

Nuclear magnetic resonance (NMR) is one of the most powerful analytical techniques. In order to obtain high-quality NMR spectra, a real-time Zangger-Sterk (ZS) pulse sequence is employed to collect low-quality pure shift NMR data with high efficiency. Then, a neural network named AC-ResNet and a loss function named SM-CDMANE are developed to train a network model. The model with excellent abilities of suppressing noise, reducing line widths, discerning peaks, and removing artifacts is utilized to process the acquired NMR data. The processed spectra with noise and artifact suppression and small line widths are ultraclean and high-resolution. Peaks overlapped heavily can be resolved. Weak peaks, even hidden in the noise, can be discerned from noise. Artifacts, even as high as spectral peaks, can be removed completely while not suppressing peaks. Eliminating perfectly noise and artifacts and smoothing baseline make spectra ultraclean. The proposed methodology would greatly promote various NMR applications.

Eight-channel C-Band demultiplexer based on one-dimensional photonic crystals defected with lithium niobate

We propose an eight-channel Dense Wavelength Division Demultiplexer (DWDM) device based on one-dimensional photonic crystal (1-D PC) structures defected with lithium niobate (LiNbO3) thin films. The demultiplexer operates in the C-band window (1460–1560 nm), which belongs to the ITU grid for DWDM applications. The desired output wavelength is achieved by applying the proper external electric field to the LiNbO3 layer at various temperatures. The transfer matrix method (TMM) is used to simulate the transmittance spectrum. Efficient output channels with transmittances of about 90% are attained. An excellent quality factor of 30919 and a very small line width of 0.05 nm are exceptional values acquired by the output channels. A very small channel spacing of 0.182 nm is attained without compromising the crosstalk, which reaches a minimum value of −34 dB. The astounding characteristics of the eight channels reveal that the proposed demultiplexer could be a potentially efficient device for DWDM networks.

Isotope Effects on the Optical Phonons of Cubic Boron Phosphide

The ratio of boron isotopes (10B and 11B) affects the thermal conductivity of cubic borides because of the phonon scattering. There are two signals appearing in the Raman spectra of cubic boron phosphide (c‐BP) single crystals with natural boron isotope abundance. One is a sharp peak with high intensity and small linewidth, which has been identified as a TO‐LO‐mixed mode; the other is a small peak in the low‐frequency side with quite low intensity and large linewidth, which is difficult to be observed in isotope‐purified crystals and with an unclear origin. Herein, in order to clarify the isotope effects on optical phonons and to identify the origin of the small peak in c‐BP, the Raman spectra of isotope‐tailored c‐BP single crystals in the range from nearly pure c‐10BP to nearly pure c‐11BP are analyzed in detail. Both the frequency and linewidth of the TO‐LO‐mixed mode are closely related to the boron isotope ratio under the isotopic average mass effect and mass disorder effect. The small Raman peak is also isotope dependent. It originates from LO phonon scattering at the non‐origin of the Brillouin zone under the isotopic mass disorder effect.

Exploring extreme conditions for star formation: A deep search for molecular gas in the Leo ring

Aims. We carried out sensitive searches for the 12CO J = 1–0 and J = 2–1 lines in the giant extragalactic HI ring in Leo to investigate the star formation process within environments where gas metallicities are close to solar, but physical conditions are different than those typical of bright galaxy disks. Our aim is to check the range of validity of known scaling relations. Methods. We used the IRAM-30 m telescope to observe 11 regions close to HI gas peaks or where sparse young massive stars have been found. For all pointed observations we reached spectral noise between 1 and 5 mK for at least one of the observed frequencies at 2 km s−1 spectral resolution. Results. We marginally detect two 12CO J = 1–0 lines in the star-forming region Clump 1 of the Leo ring, whose radial velocities are consistent with those of Hα lines, but whose line widths are much smaller than observed for virialized molecular clouds of similar mass in galaxies. The low signal-to-noise ratio, the small line widths, and the extremely low number densities inferred by virialized cloud models suggest that a more standard population of molecular clouds, still undetected, might be in place. Using upper limits to the CO lines, the most sensitive pointed observations show that the molecular gas mass surface density is lower than expected from the extrapolation of the molecular Kennicutt–Schmidt relation established in the disk of galaxies. The sparse stellar population in the ring, possibly forming ultra diffuse dwarf galaxies, might then be the result of a short molecular gas depletion time in this extreme environment.

3D conductive scaffolds of MXene@PCL with high conductivity and small line width fabricated by electric-field-driven jet 3D printing and electrostatic self-assembly

There has been an increasing interest in 3D conductive scaffolds due to their unique ability to promote cell growth, proliferation, and differentiation. However, preparing 3D conductive scaffolds with high resolution and high conductivity still faces great challenges. Herein, a new method combining electric-field-driven (EFD) jet 3D printing and electrostatic self-assembly (ESA) is proposed to prepare 3D conductive scaffolds of MXene@PCL with high conductivity and small line widths. Firstly, the effect of EFD jet 3D printing processing parameters on the line width and the effect of ESA on the conductivity has been investigated and optimized. Based on the optimized parameters, the prepared 3D conductive scaffolds of MXene@PCL with a line width of 12 µm exhibit excellent performance: tensile stress of 2.67 MPa, elongation of 523.9 %, the porosity of 88.4 %, the conductivity of 2.8 ± 0.3 S cm−1, which is much higher than the reported results. Furthermore, the electrical conductivity can still reach 2.12 ± 0.1 S cm−1 after 100 cycles of bending at 120°, indicating the good adhesion between MXene and PCL matrix. Therefore, the proposed fabrication method offers a promising application prospect for 3D conductive scaffolds with high conductivity and small line widths in regenerative medicine.

Advances in multi-wavelength Brillouin fiber lasers: An outlook across different spectral regions

In recent years, Brillouin fiber lasers have become a promising optical source technology for academic and industrial purposes. Among the promising laser solutions that have emerged with low threshold, high efficiency, small linewidth, and low resonator loss, multi-wavelength architecture has attracted the most attention recently. However, the development of configurations with an increased number of Stokes channels that present high flatness and reasonable optical-to-signal ratio (OSNR) is a challenge that this fiber laser technology still faces, and the development of solutions for this is an open problem. From this perspective, this paper presents a review focused on recent progress in multi-wavelength Brillouin fiber laser (MBFL) devices. Specifically, microwave generation and temperature sensing applications are discussed. Key results in the spectral regions of 1.0μm, 1.3μm, 1.5μm, 1.6μm, and 2.0μm are reported, as well as future perspectives are addressed in this review for the advancements in multi-wavelength fiber laser sources.

First-principles study of the temperature-induced band renormalization in thermoelectric filled skutterudites.

Band structure characteristics, such as band gap and band dispersion, are fundamental properties of materials. Temperature can affect them because of lattice expansion and phonon-induced atomic vibrations. Here, we apply the recently developed electron-phonon renormalization method to study the temperature effect on the band structures of thermoelectric (TE) filled skutterudites BaCo4Sb12, BaFe4Sb12, and YbFe4Sb12 from first-principles. The results reveal that the band gap in BaCo4Sb12 drops slower with temperature compared with our previous study on CoSb3, where it considerably reduces from 0 K to 800 K for BaFe4Sb12 (∼0.222 eV) and YbFe4Sb12 (∼0.201 eV). Furthermore, the band dispersions near the band edges at the Γ-point in the three systems at high temperatures are similar to those at 0 K, and the electron energies have small linewidths, whereas the linewidths for energies near the Fermi level are large. The different phenomena are due to the different phonon vibration-induced electronic structure disorders, reflecting the strength of electron-phonon coupling. Band renormalization would further affect the TE properties of these filled skutterudites. Our work provides a deeper understanding of the temperature-dependent band structure in skutterudites.

Influence of the apparatus on the intensity ratio of the measured Raman peaks

We report an analytic result about the influence of the apparatus on the intensity ratio of the Raman peaks. This ratio of the Raman peak with the larger linewidth to the one with the smaller linewidth will increase with the increasing width of the instrument response function and the linewidth of the incident laser. For the applications of the empirical equations based on the intensity ratio of Raman peaks, the spectral resolution of the instrument should be indicated, and the fitting associated with a measured instrument response function is recommended.

High Sensitivity Spin Defects in hBN Created by High‐Energy He Beam Irradiation

AbstractRecently the negatively charged boron vacancies () in hexagonal boron nitride (hBN) have been shown as spin defects that have great potential in quantum sensing. However, so far the sensitivity is limited by either photoluminescence (PL) intensity or the optically detected magnetic resonance (ODMR) contrast, and linewidth. In this work, the generation of these spin defects is demonstrated using high‐energy helium ion beams, and ODMR measurements with different laser and microwave powers are performed. The spin defects generated by high‐energy helium ions exhibit a high PL intensity and ODMR contrast while keeping a small linewidth, hence a good sensitivity. By comparing different fluences of helium irradiations, an optimal fluence is determined which is sufficient in creating spin defects without damaging the overall crystal lattice structure. With this optimal fluence, a high signal‐to‐noise ratio ODMR spectrum can be obtained with an accurate measurement of zero‐field splitting frequency, and a best sensitivity as . Moreover, with a focused beam, such spin defects can be created deterministically with nanometer precision.