Enhanced detection limit in an exceptional surface-based fiber resonator by manipulating Fano interference.

An exceptional surface (ES) has advantages in improving sensing robustness and enhancing frequency splitting. Typically, the eigenvalue splitting must exceed the mode linewidth in order to be clearly visible in the spectrum, which limits the precision of the ES-based sensing structure. In this paper, a strategy for manipulating spectral line shape in an ES-based structure is experimentally realized. In addition, the limit of the minimum detectable displacement can be further reduced by monitoring the peak intensity of the Fano interference line shape. The demonstration of Fano interference in an ES-based system opens the way for a new class of ultrasensitive optical sensors.

Stable and Tunable Quantum Conductance in Spider-Silk-like Synaptic Device for Neurocomputing.

The quantum conductance (QC) behaviors in synaptic devices with stable and tunable conductance states are essential for high-density storage and brain-like neurocomputing (NC). In this work, inspired by the discontinuous transport of fluid in spider silk, a synaptic device composed of a silicon oxide nanowire network embedded with silicon quantum dots (Si-QDs@SiOx) is designed. The tunable QC behaviors are achieved in both the SET and RESET processes, and the QC states exhibit stable retention time exceeding 104 s in the synaptic device and show stable reproducibility after an interval of two months. The synaptic plasticity, including long-term potentiation/depression and Pavlovian conditioning function, is simulated based on the tunable conductance. The mechanism of stable and tunable QC behaviors is analyzed and clarified by beading effect of spider silk in Si-QDs@SiOx nanowires structure. The digit recognition capability of the device is evaluated by simulation using an artificial neural network consisting of the Si-QDs@SiOx-based synaptic device. These results provide insights into the development of neurocomputing systems with high classification accuracy.

Controllability of the Conductive Filament in Porous SiOx Memristors by Humidity-Mediated Silver Ion Migration.

Oxide-based memristors composed of Ag/porous SiOx/Si stacks are fabricated using different etching time durations between 0 and 90 s, and the memristive properties are analyzed in the relative humidity (RH) range of 30-60%. The combination of humidity and porous structure provides binding sites to control silver filament formation with a confined nanoscale channel. The memristive properties of devices show high on/off ratios up to 108 and a dispersion coefficient of 0.1% of the high resistance state (CHRS) when the RH increases to 60%. Humidity-mediated silver ion migration in the porous SiOx memristors is investigated, and the mechanism leading to the synergistic effects between the porous structure and environmental humidity is elucidated. The artificial neural network constructed theoretically shows that the recognition rate increases from 60.9 to 85.29% in the RH range of 30-60%. The results and theoretical understanding provide insights into the design and optimization of oxide-based memristors in neuromorphic computing applications.

A High-Performance Magnetic Shield with MnZn Ferrite and Mu-Metal Film Combination for Atomic Sensors.

This study proposes a high-performance magnetic shielding structure composed of MnZn ferrite and mu-metal film. The use of the mu-metal film with a high magnetic permeability restrains the decrease in the magnetic shielding coefficient caused by the magnetic leakage between the gap of magnetic annuli. The 0.1-0.5 mm thickness of mu-metal film prevents the increase of magnetic noise of composite structure. The finite element simulation results show that the magnetic shielding coefficient and magnetic noise are almost unchanged with the increase in the gap width. Compared with conventional ferrite magnetic shields with multiple annuli structures under the gap width of 0.5 mm, the radial shielding coefficient increases by 13.2%, and the magnetic noise decreases by 21%. The axial shielding coefficient increases by 22.3 times. Experiments verify the simulation results of the shielding coefficient of the combined magnetic shield. The shielding coefficient of the combined magnetic shield is 16.5%. It is 91.3% higher than the conventional ferrite magnetic shield. The main difference is observed between the actual and simulated relative permeability of mu-metal films. The combined magnetic shielding proposed in this study is of great significance to further promote the performance of atomic sensors sensitive to magnetic field.

Ambipolar steep-slope nanotransistors with Janus MoSSe/graphene heterostructures.

The transfer characteristics and switching mechanism of the steep-slope transistor composed of the graphene/Janus MoSSe heterostructure are investigated by quantum transport calculation. The Schottky barrier height at the Gr/SMoSe interface and tunneling width between the channel and drain can be tuned by the gate voltage, so that the device exhibits ambipolar switching with two minima in the subthreshold swing slope. 34 and 29 mV decade-1subthreshold swings can be achieved and the on/off ratios are over 106and 108for the different switching mechanisms. The device provides a solution and guidance for the future design of low-power, high-performance devices.

Analysis of effects of magnetic field gradient on atomic spin polarization and relaxation in optically pumped atomic magnetometers.

The magnetic field gradient within optical pumping magnetometers (OPMs) suppresses sensitivity improvement. We investigated the effects of the magnetic field gradient along the x-, y-, and z-axes on the limiting factors of magnetometers under extremely low magnetic field conditions. We modified the magnetic field gradient relaxation model such that it can be applied to atoms in the spin exchange relaxation free (SERF) regime. The gradient relaxation time and spin polarizations, combined with fast spin-exchange interaction, were determined simultaneously using the oscillating cosine magnetic field excitation and amplitude spectrum analysis method. During the experiments, we eliminated the errors caused by the temperature and pumping power, and considered different isotope spin exchange collisions in naturally abundant Rb during the data analysis to improve the fitting accuracy. The experimental results agreed well with those of theoretical calculations and confirmed the accuracy of the improved model. The contribution of the transverse magnetic field gradient to the relaxation of the magnetic field gradient cannot be ignored in the case of small static magnetic fields. Our study provides a theoretical and experimental basis for eliminating magnetic gradient relaxation in atomic sensors in the SERF region.

Giant and tunable Goos-Hänchen shift with a high reflectance induced by PT-symmetry in atomic vapor.

The Goos-Hänchen (GH) shifts of light beams reflected from conventional passive optical systems could be enhanced using the Brewster angle effect or resonance effect, but the maximum GH shift is located at the reflectance minima, which is difficult for experimental detection. In this paper, we present an efficient and flexible scheme to realize complex parity-time (PT)-symmetric periodic optical potentials (complex crystals) in helium atomic vapor. The GH shifts of probe light reflected from the complex crystal are theoretically investigated and large GH shifts could be obtained inside the high-reflection band. When the complex crystal is operated near the coherent perfect absorption-laser point, the maximum GH shift of probe light is exactly located at the reflectance peak. Moreover, the GH shifts could be easily controlled by adjusting the intensity of control light.

GaOx@GaN Nanowire Arrays on Flexible Graphite Paper with Tunable Persistent Photoconductivity.

Flexible optoelectronic synaptic devices that functionally imitate the neural behavior with tunable optoelectronic characteristics are crucial to the development of advanced bioinspired neural networks. In this work, amorphous oxide-decorated GaN nanowire arrays (GaOx@GaN NWAs) are prepared on flexible graphite paper. A GaOx@GaN NWA-based flexible device has tunable persistent photoconductivity (PPC) and shows a conversible fast/slow decay process (SDP). Photoconductivity can be modulated by single or double light pulses with different illumination powers and biases. PPC gives rise to the high-performance SDP such as a long decay time of 2.3 × 105 s. The modulation mechanism is proposed and discussed. Our results reveal an innovative and efficient strategy to produce decorated NWAs on a flexible substrate with tunable optoelectronic properties and exhibit potential for flexible neuromorphic system applications.

Effect of Oleamine on Microwave-Assisted Synthesis of Cesium Lead Bromide Perovskite Nanocrystals.

Herein, we reported a simple microwave-assisted method for synthesizing uniform CsPbBr3 and Cs4PbBr6 perovskite nanocrystals (PeNCs). The phase structure, photoluminescence (PL) emission, and quantum yield (QY) of CsPbBr3 PeNCs can be tuned by changing the radiation time and power of the microwave. The optimized CsPbBr3 PeNCs showed a high PLQY of up to 87%. The transformation from green-luminescent three-dimensional (3D) CsPbBr3 PeNCs to nonluminescent zero-dimensional (0D) Cs4PbBr6 PeNCs was easily realized by adjusting the amount of oleamine (OAm) and oleic acid (OA), and the changes in morphology and phase structure during the transformation process were studied by a microwave-assisted technique. Meanwhile, the optical properties of Cs4PbBr6 PeNCs were revealed by monitoring the changes in absorption and emission spectra. Furthermore, through first-principles calculations based on density functional theory (DFT), the luminescene origination of as-prepared PeNCs was further explained. In this work, we controlled the phase transition from CsPbBr3 to Cs4PbBr6 through a simple method, which provides a strategy for other types of perovskite phase transitions.

High spatial resolution multi-channel optically pumped atomic magnetometer based on a spatial light modulator.

Ultra-sensitive multi-channel optically pumped atomic magnetometers based on the spin-exchange relaxation-free (SERF) effect are powerful tools for applications in the field of magnetic imaging. To simultaneously achieve ultra-high spatial resolution and ultra-high magnetic field sensitivity, we proposed a high-resolution multi-channel SERF atomic magnetometer for two-dimensional magnetic field measurements based on a digital micro-mirror device (DMD) as the spatial light modulator for a single vapor cell. Under the optimal experimental conditions obtained via spatial and temporal modulation of the probe light, we first demonstrated that the average sensitivity of the proposed 25-channel magnetometer was approximately 25fT/Hz1/2 with a spatial resolution of 216µm. Then, we measured the magnetic field distribution generated by a gradient coil and compared the experimentally obtained distributions with those calculated via finite element simulation. The obtained g value of 99.2% indicated good agreement between our experimental results and the theoretical calculations, thereby confirming that our proposed multi-channel SERF magnetometer was effective at measuring magnetic field distributions with an ultra-high spatial resolution.

Strain-enhanced power conversion efficiency of a BP/SnSe van der Waals heterostructure.

A promising BP/SnSe van der Waals (vdW) photovoltaic heterostructure was designed and investigated by first-principles calculations. The BP/SnSe vdW heterostructure showed inhibition of photogenerated carrier recombination as well as broad and high optical absorption intensity spanning the visible to deep ultraviolet regions reaching the order of 105 cm-1. The carrier mobility of the BP/SnSe vdW heterostructure exhibited anisotropic characteristics reaching approximately 103 cm2 V-1 s-1, with an intrinsic power conversion efficiency (PCE) of 11.96%. Our results show that the PCE can be increased to 17.24% when the conduction band offset between BP and SnSe is reduced by strain engineering. The distinctive and favorable properties suggest that the BP/SnSe vdW heterostructure has great potential for use in photovoltaic devices.

Fabrication of a Hierarchical Ni(OH)2 @Ni3 S2 /Ni Foam Electrode from a Prussian Blue Analogue-Based Composite with Enhanced Electrochemical Capacitive and Electrocatalytic Properties.

Developing high-efficiency, cost-effective, and durable electrodes is significant for electrochemical capacitors and electrocatalysis. Herein, a 3D bifunctional electrode consisting of nickel hydroxide nanosheets@nickel sulfide nanocubes arrays on Ni foam (Ni(OH)2 @Ni3 S2 /NF) obtained from a Prussian blue analogue-based precursor is reported. The 3D higher-order porous structure and synergistic effect of different compositions endow the electrode with large specific surface area, facile ion/electron transport path, and improved conductivity. As a result, the Ni(OH)2 @Ni3 S2 /NF electrode exhibits a high specific capacity of 211 mA h g-1 at a current density of 1 A g-1 and 73 % capacity retention after 5000 cycles at 5 A g-1 . Moreover, the Ni(OH)2 @Ni3 S2 /NF electrode has superior electrocatalytic activity for the hydrogen evolution reaction with low overpotentials of 140 and 210 mV at current densities of 10 and 100 mA cm-2 , respectively. The synthetic strategy for the unique higher-order porous structure can be extended to fabricate other composite materials for energy storage and conversion.

Stability and Repeatability of a Karst-like Hierarchical Porous Silicon Oxide-Based Memristor.

A memristor architecture based on porous oxide materials has the potential to be used in artificial synaptic devices. Herein, we present a memristor system employing a karst-like hierarchically porous (KLHP) silicon oxide structure with good stability and repeatability. The KLHP structure prepared by an electrochemical process and thermal oxidation exhibits high ON-OFF ratios up to 105 during the endurance test, and the data can be maintained for 105 s at a small read voltage 0.1 V. The mechanism of lithium ion migration in the porous silicon oxide structure has been discussed by a simulated model. The porous silicon oxide-based memristor is very promising because of the enhanced performance as well as easily accessed neuromorphic computing.

Lithium ion trapping mechanism of SiO2 in LiCoO2 based memristors.

Pt/LiCoO2/SiO2/Si stacks with different SiO2 thicknesses are fabricated and the influence of SiO2 on memristive behavior is investigated. It is demonstrated that SiO2 can serve as Li ion trapping layer benefiting device retention, and the thickness of SiO2 must be controlled to avoid large SET voltage and state instability. Simulation model based on Nernst potential and diffusion potential is postulated for electromotive force in LiCoO2 based memristors. The simulation results show that SiO2 trapping layer decreases the total electromotive field of device and thereby prevents Li ions from migrating back to LiCoO2. This model shows a good agreement with experimental data and reveals the Li ion trapping mechanism of SiO2 in LiCoO2 based memristors.

Tunable band offsets in the BP/P4O10 van der Waals heterostructure: first-principles calculations.

The structural and electronic properties of the black phosphorus/phosphorus pentoxide (BP/P4O10) van der Waals (vdW) heterostructure are investigated theoretically by first-principles calculations. The BP/P4O10 vdW heterostructure is a direct bandgap semiconductor with intrinsic type-II band alignment thus facilitating separation of photoexcited charge carriers. A transition from semiconducting to metallic is predicted under a positive electric field and the transition of type-II to type-I band alignment occurs under a negative electric field in the BP/P4O10 vdW heterostructure. Moreover, the bandgap can be modulated by adjusting the interlayer distance. The results indicate that the band offsets of the BP/P4O10 vdW heterostructure are tunable, consequently boding well for application to nanoelectronics and optoelectronics.

Theoretical analyses of resonant frequency shift in anomalous dispersion enhanced resonant optical gyroscopes.

Rigorous expressions of resonant frequency shift (RFS) in anomalous dispersion enhanced resonant optical gyroscopes (ADEROGs) are deduced without making approximation, which provides a precise theoretical guidance to achieve ultra-sensitive ADEROGs. A refractive index related modification factor is introduced when considering special theory of relativity (STR). We demonstrate that the RFS will not be "infinitely large" by using critical anomalous dispersion (CAD) and negative modification does not exist, which make the mechanism of anomalous dispersion enhancement clear and coherent. Although step change of RFS will happen when the anomalous dispersion condition varies, the amplification of RFS is limited by attainable variation of refractive index in practice. Moreover, it is shown that the properties of anomalous dispersion will influence not only the amplification of RFS, but also the detection range of ADEROGs.

On-chip modulation for rotating sensing of gyroscope based on ring resonator coupled with Mach-Zehnder interferometer.

An improving structure for resonance optical gyro inserting a Mach-Zehnder Interferomete (MZI) into coupler region between ring resonator and straight waveguide was proposed. The different reference phase shift parameters in the MZI arms are tunable by thermo-optic effect and can be optimized at every rotation angular rate point without additional phase bias. Four optimum paths are formed to make the gyroscope to work always at the highest sensitivity.

[Histological analysis of the anterior lobe region in transurethral prostatectomy].

OBJECTIVE: To explore the possibility of injury to the striated urethral sphincter by incision to the anterior lobe region in transurethral prostatectomy. METHODS: We incised the anterior lobe region of 60 patients with benign prostatic hyperplasia (BPH) undergoing transurethral prostatectomy. The patients were divided into four groups according to the incision fields: proximate superficial (group 1), proximate deep (group 2), distal superficial (group 3) and distal deep (group 4). The tissues taken from the anterior lobe region were subjected to HE staining, and the smooth and striated muscles were detected by immunohistochemical identification of smooth muscle actin (SMA) and myoglobin (MYO) in the tissues. The prostate volume, age, and PSA level of the patients were analyzed against their positive or negative results. The relative contents of the striated muscle were compared among groups 2, 3 and 4. The independent-sample between-group t-test was used for statistic analysis. RESULTS: The urethral rhabdosphincter was found in the anterior lobe region, with the smooth muscle intermixed with the striated muscle. The incision injury of the urethral rhabdosphincter was associated with the prostate volume. Increased urethral rhabdosphincter was observed in the anterior lobe region, approaching the apex of the prostate and extending to the urethral lumen. CONCLUSION: The anterior lobe region should not be excessively incised in transurethral prostatectomy so as to avoid direct injury of the striated urethral sphincter, which is especially important for prostates of smaller volume or operation near the apex of the prostate.

Improved infrared emissions of Er(3+)-Tm3+ co-doped Al2O3 thin films: the role of cross relaxation among rare earth ions.

We report the infrared emissions of Er(3+)-Tm3+ co-doped amorphous Al2O3 thin films pumped at 791 nm by a Ti:sapphire laser. The as-deposited films were annealed to improve the photoluminescence performance. Three cross relaxation channels among Er(3+)-Tm3+ and Tm(3+)-Tm3+ ions incorporated in the films were investigated as annealing temperature increases especially from 800 to 850 degrees C. In order to understand the Stark effect and cross relaxations, the photoluminescence spectra were deconvoluted by Gaussian fittings. Our results indicate that the luminescence intensity of 1.62 microm in comparison to 1.5 microm can be enhanced by the cross relaxation process [Er3+ (4I13/2) + Tm3+ (3H6) --> Er3+ (4I15/2) + Tm3+ (3F4)], and the longer-wavelength side of Er3+ emission can be improved by the CR process [Er3+ (4I15/2) + Tm3+ (3H4) --> Er3+ (4I3/2) + Tm3+ (3F4) at expense of the Tm3+ 1.47 microm emission which is also maybe quenched by the CR effect between themselves. These results suggest one possible approach to achieve broadband infrared emissions at the wavelength region of 1.45-1.65 microm from the Er(3+)-Tm3+ co-doped systems.

Photoluminescence and energy transfer study of Er3+ and Dy3+ codoped tellurite glasses.

Photoluminescence properties of the Er(3+)-Dy3+ codoped tellurite glasses were studied by absorption and visible emission spectra, which revealed luminescence bands of both Er3+ and Dy3+ when pumping with the wavelength of 325 nm. The concentration quenching occurred as Dy3+ concentration increased beyond 3 mol%. The dependence of Er3+ characteristic emission on Dy3+ concentration indicated energy transfer process between Er3+ and Dy3+. The chromaticity coordinates of these glasses are close to white light, which implies that these glasses might be potential candidates for white lighting through an appropriate combination.