Unlocking Efficient Ultrafast Bound-Electron Optical Nonlinearities via Mirror Induced Quasi Bound States in the Continuum.

The operation of photonic devices often relies on modulation of their refractive index. While the sub-bandgap index change through bound-electron optical nonlinearity offers a faster response than utilizing free carriers with an overbandgap pump, optical switching often suffers from inefficiency. Here, we use a recently observed metasurface based on mirror-induced optical bound states in the continuum, to enable superior modulation characteristics. We achieve a pulsewidth-limited switching time of 100 fs, reflectance change of 22%, remarkably low energy consumption of 255 µJ/cm2, and an enhancement of modulation contrast by a factor of 440 compared to unpatterned silicon. Additionally, the narrow photonic resonance facilitates the detection of the dispersive nondegenerate two-photon nonlinearity, allowing tunable pump and probe excitation. These findings are explained by a two-band theoretical model for the dispersive nonlinear index. The demonstrated efficient and rapid switching holds immense potential for applications, including quantum photonics, sensing, and metrology.

MilliKelvin microwave impedance microscopy in a dry dilution refrigerator.

Microwave impedance microscopy (MIM) is a near-field imaging technique that has been used to visualize the local conductivity of materials with nanoscale resolution across the GHz regime. In recent years, MIM has shown great promise for the investigation of topological states of matter, correlated electronic states, and emergent phenomena in quantum materials. To explore these low-energy phenomena, many of which are only detectable in the milliKelvin regime, we have developed a novel low-temperature MIM incorporated into a dilution refrigerator. This setup, which consists of a tuning-fork-based atomic force microscope with microwave reflectometry capabilities, is capable of reaching temperatures down to 70 mK during imaging and magnetic fields up to 9 T. To test the performance of this microscope, we demonstrate microwave imaging of the conductivity contrast between graphite and silicon dioxide at cryogenic temperatures and discuss the resolution and noise observed in these results. We extend this methodology to visualize edge conduction in Dirac semi-metal cadmium arsenide in the quantum Hall regime.

Adiabatic topological photonic interfaces.

Topological phases of matter have been attracting significant attention across diverse fields, from inherently quantum systems to classical photonic and acoustic metamaterials. In photonics, topological phases offer resilience and bring novel opportunities to control light with pseudo-spins. However, topological photonic systems can suffer from limitations, such as breakdown of topological properties due to their symmetry-protected origin and radiative leakage. Here we introduce adiabatic topological photonic interfaces, which help to overcome these issues. We predict and experimentally confirm that topological metasurfaces with slowly varying synthetic gauge fields significantly improve the guiding features of spin-Hall and valley-Hall topological structures commonly used in the design of topological photonic devices. Adiabatic variation in the domain wall profiles leads to the delocalization of topological boundary modes, making them less sensitive to details of the lattice, perceiving the structure as an effectively homogeneous Dirac metasurface. As a result, the modes showcase improved bandgap crossing, longer radiative lifetimes and propagation distances.

Spatial Interactions in Hydrogenated Perovskite Nickelate Synaptic Networks.

A key aspect of how the brain learns and enables decision-making processes is through synaptic interactions. Electrical transmission and communication in a network of synapses are modulated by extracellular fields generated by ionic chemical gradients. Emulating such spatial interactions in synthetic networks can be of potential use for neuromorphic learning and the hardware implementation of artificial intelligence. Here, we demonstrate that in a network of hydrogen-doped perovskite nickelate devices, electric bias across a single junction can tune the coupling strength between the neighboring cells. Electrical transport measurements and spatially resolved diffraction and nanoprobe X-ray and scanning microwave impedance spectroscopic studies suggest that graded proton distribution in the inhomogeneous medium of hydrogen-doped nickelate film enables this behavior. We further demonstrate signal integration through the coupling of various junctions.

Hydrocortisone versus vasopressin for the management of adult patients with septic shock refractory to norepinephrine: A multicenter retrospective study.

STUDY OBJECTIVE: Significant practice variation exists when selecting between hydrocortisone and vasopressin as second line agents in patients with septic shock in need of escalating doses of norepinephrine. The goal of this study was to assess differences in clinical outcomes between these two agents. DESIGN: Multicenter, retrospective, observational study. SETTING: Ten Ascension Health hospitals. PATIENTS: Adult patients with presumed septic shock receiving norepinephrine prior to study drug initiation between December 2015 and August 2021. INTERVENTION: Vasopressin (0.03-0.04 units/min) or hydrocortisone (200-300 mg/day). MEASUREMENTS AND MAIN RESULTS: A total of 768 patients were included with a median (interquartile range) SOFA score of 10 (8-13), norepinephrine dose of 0.3 mcg/kg/min (0.1-0.5 mcg/kg/min), and lactate of 3.8 mmol/L (2.4-7.0 mmol/L) at initiation of the study drug. A significant difference in 28-day mortality was noted favoring hydrocortisone as an adjunct to norepinephrine after controlling for potential confounding factors (OR 0.46 [95% CI, 0.32-0.66]); similar results were seen following propensity score matching. Compared to vasopressin, hydrocortisone initiation was also associated with a higher rate of hemodynamic responsiveness (91.9% vs. 68.2%, p < 0.01), improved resolution of shock (68.8% vs. 31.5%, p < 0.01), and reduced recurrence of shock within 72 h (8.7% vs. 20.7%, p < 0.01). CONCLUSIONS: Addition of hydrocortisone to norepinephrine was associated with a lower 28-day mortality in patients with septic shock, compared to the addition of vasopressin.

Spin-dependent properties of optical modes guided by adiabatic trapping potentials in photonic Dirac metasurfaces.

The Dirac-like dispersion in photonic systems makes it possible to mimic the dispersion of relativistic spin-1/2 particles, which led to the development of the concept of photonic topological insulators. Despite recent demonstrations of various topological photonic phases, the full potential offered by Dirac photonic systems, specifically their ability to emulate the spin degree of freedom-referred to as pseudo-spin-beyond topological boundary modes has remained underexplored. Here we demonstrate that photonic Dirac metasurfaces with smooth one-dimensional trapping gauge potentials serve as effective waveguides with modes carrying pseudo-spin. We show that spatially varying gauge potentials act unevenly on the two pseudo-spins due to their different field distributions, which enables control of guided modes by their spin, a property that is unattainable with conventional optical waveguides. Silicon nanophotonic metasurfaces are used to experimentally confirm the properties of these guided modes and reveal their distinct spin-dependent radiative character; modes of opposite pseudo-spin exhibit disparate radiative lifetimes and couple differently to incident light. The spin-dependent field distributions and radiative lifetimes of their guided modes indicate that photonic Dirac metasurfaces could be used for spin-multiplexing, controlling the characteristics of optical guided modes, and tuning light-matter interactions with photonic pseudo-spins.

Topological edge states of a long-range surface plasmon polariton at the telecommunication wavelength.

Confining light by plasmonic waveguides is promising for miniaturizing optical components, while topological photonics has been explored for robust light localization. Here we propose combining the two approaches into a simple periodically perforated plasmonic waveguide (PPW) design exhibiting robust localization of long-range surface plasmon polaritons. We predict the existence of a topological edge state originating from a quantized topological invariant, and numerically demonstrate the viability of its excitation at telecommunication wavelength using near-field and waveguide-based approaches. Strong modification of the radiative lifetime of dipole emitters by the edge state, and its robustness to disorder, are demonstrated.

Pass or Fail? Postoperative Active Voiding Trials in an Enhanced Recovery Program.

IMPORTANCE: Pelvic reconstructive surgery is often associated with transient postoperative voiding dysfunction. OBJECTIVE: This study aimed to compare postoperative active voiding trial (AVT) outcomes before and after implementation of an enhanced recovery program (ERP) for women undergoing pelvic reconstructive surgery. In addition, risk factors for postoperative urinary retention were identified. STUDY DESIGN: We retrospectively identified patients undergoing inpatient vaginal or robotic pelvic reconstructive surgery before and after implementation of an ERP at our institution. Demographics, operative and postoperative details, and AVT outcomes were collected. Primary outcome was AVT failure. Variables associated with increased risk of AVT failure were identified using multivariate analysis. RESULTS: Three hundred seventeen patients were included-75 pre-ERP and 242 ERP. There was no difference in AVT failures between pre-ERP and ERP groups (21.3% vs 21.9%, P = 0.92). The AVT failures were highest among those with abnormal preoperative postvoid residual volume (PVR ≥100 mL, 25.9% vs 12.2%, P = 0.01) and those who underwent an incontinence procedure (midurethral sling or Kelly plication, 30.4% vs 16.9%, P = 0.01). Compared with a reference procedure (total vaginal hysterectomy [TVH]), the following procedures were associated with statistically significant higher odds ratios (ORs) of AVT failure: TVH with incontinence procedure (OR, 15.0; confidence interval [CI], 4.58-48.9; P < 0.001), TVH with anterior repair (OR, 4.98; CI, 1.93-12.9; P = 0.001), and robotic sacrocolpopexy (OR, 3.6; CI, 1.18-11.2; P = 0.02). CONCLUSIONS: Postoperative AVT failure incidence did not differ pre- and post-ERP intervention. Abnormal preoperative PVR was associated with failed postoperative voiding trial. Concomitant incontinence procedures and/or anterior colporrhaphy were associated with increased incidence of voiding trial failure regardless of ERP cohort.

Near-field mapping of high permittivity dielectric microwave resonator modes via optically induced conductance.

In this paper, we demonstrate a straightforward, low-cost, and high resolution optical-based method to measure the three-dimensional relative electric field magnitude in microwave circuits without the need to monitor reflected laser beams or the requirement of photoconductive substrates for the device under test. The technique utilizes optically induced conductance, where a focused laser beam excites electron-hole-pairs (EHPs) in a semiconductor thin film placed in the near-field of a microwave circuit. The generated EHPs create localized loss in the resonator and modulate the transmitted microwave signal, proportional to the local microwave electric field. As a proof of principle, several different modes of a high permittivity (ɛ ∼ 80) cylindrical dielectric resonator are mapped.

Optical Bound States in the Continuum Enabled by Magnetic Resonances Coupled to a Mirror.

Dielectric metasurfaces made of high refractive index and low optical loss materials have emerged as promising platforms to achieve high-quality factor modes enabling strong light-matter interaction. Bound states in the continuum have shown potential to demonstrate narrow spectral resonances but often require asymmetric geometry and typically feature strong polarization dependence, complicating fabrication and limiting practical applications. We introduce a novel approach for designing high-quality bound states in the continuum using magnetic dipole resonances coupled to a mirror. The resulting metasurface has simple geometric parameters requiring no broken symmetry. To demonstrate the unique features of our photonic platform we show a record-breaking third harmonic generation efficiency from the metasurface benefiting from the strongly enhanced electric field at high-quality resonances. Our approach mitigates the shortcomings of previous platforms with simple geometry enabling facile and large-area fabrication of metasurfaces paving the way for applications in optical sensing, detection, quantum photonics, and nonlinear devices.

The RUMERTIME Process as a Protective Factor in School Attendance Problems.

The RUMERTIME Process (RP) is a five-step culturally responsive social-emotional, problem-solving, prevention-intervention strategy used to educate, equip, and empower students, educators, and families. The RP equips individuals with the abilities to recognize, understand, manage, express, and reflect on their thoughts, interactions, mindsets, and emotions (RUMERTIME) in relation to themselves, others, and the daily life challenges they face within multiple systems and settings. The RP is embedded within the Cultivating SEEDS System framework (CSS) and is utilized to equip culturally diverse communities, inclusive of students, family members, educators, and administrators, with the social-emotional skills to effectively solve student attendance problems (SAPs). The data shared in this practice intervention article are descriptive in nature and highlight the RP as a protective factor and explain its three goals. The paper consists of three parts: (a) introduction of the RP, which is embedded in the CSS framework; (b) description of implementation of the RP as integral to the Daytime Intervention Room (DIR) program; and (c) discussion of risk factors that qualified students to receive services through the DIR program as well as data that demonstrated how the RP performed as a protective factor. The DIR program was aimed at creating an alternative to out-of-school suspension (OSS) and the traditional punitive in-school suspension (ISS). The program was established in each of the four schools in an urban high-needs school district in the midwest region of the United States. The DIR program was intentionally designed to include multiple levels, stakeholders, and delivery support, thus creating a solid base for the holistic development of students, educators, and parents. In conjunction with the CSS framework, the DIR program sought to increase academic performance, decrease the number of behavior referrals, and improve attendance rates in this high-needs urban school district.

Silicon-nitride microring resonators for nonlinear optical and biosensing applications.

We discuss the design, fabrication, and characterization of silicon-nitride microring resonators for nonlinear-photonic and biosensing device applications. The first part presents new theoretical and experimental results that overcome highly normal dispersion of silicon-nitride microresonators by adding a dispersive coupler. The latter parts review our work on highly efficient second-order nonlinear interaction in a hybrid silicon-nitride slot waveguide with nonlinear polymer cladding and silicon-nitride microring application as a biosensor for human stress indicator neuropeptide Y at the nanomolar level.

Broadband GaAsSb Nanowire Array Photodetectors for Filter-Free Multispectral Imaging.

Highly compact, filter-free multispectral photodetectors have important applications in biological imaging, face recognition, and remote sensing. In this work, we demonstrate room-temperature wavelength-selective multipixel photodetectors based on GaAs0.94Sb0.06 nanowire arrays grown by metalorganic vapor phase epitaxy, providing more than 10 light detection channels covering both visible and near-infrared ranges without using any optical filters. The nanowire array geometry-related tunable spectral photoresponse has been demonstrated both theoretically and experimentally and shown to be originated from the strong and tunable resonance modes that are supported in the GaAsSb array nanowires. High responsivity and detectivity (up to 44.9 A/W and 1.2 × 1012 cm √Hz/W at 1 V, respectively) were obtained from the array photodetectors, enabling high-resolution RGB color imaging by applying such a nanowire array based single pixel imager. The results indicate that our filter-free wavelength-selective GaAsSb nanowire array photodetectors are promising candidates for the development of future high-quality multispectral imagers.

Light Absorption in Nanowire Photonic Crystal Slabs and the Physics of Exceptional Points: The Shape Shifter Modes.

Semiconductor nanowire arrays have been demonstrated as promising candidates for nanoscale optoelectronics applications due to their high detectivity as well as tunable photoresponse and bandgap over a wide spectral range. In the infrared (IR), where these attributes are more difficult to obtain, nanowires will play a major role in developing practical devices for detection, imaging and energy harvesting. Due to their geometry and periodic nature, vertical nanowire and nanopillar devices naturally lend themselves to waveguide and photonic crystal mode engineering leading to multifunctional materials and devices. In this paper, we computationally develop theoretical basis to enable better understanding of the fundamental electromagnetics, modes and couplings that govern these structures. Tuning the photonic response of a nanowire array is contingent on manipulating electromagnetic power flow through the lossy nanowires, which requires an intimate knowledge of the photonic crystal modes responsible for the power flow. Prior published work on establishing the fundamental physical modes involved has been based either on the modes of individual nanowires or numerically computed modes of 2D photonic crystals. We show that a unified description of the array key electromagnetic modes and their behavior is obtainable by taking into account modal interactions that are governed by the physics of exceptional points. Such models that describe the underlying physics of the photoresponse of nanowire arrays will facilitate the design and optimization of ensembles with requisite performance. Since nanowire arrays represent photonic crystal slabs, the essence of our results is applicable to arbitrary lossy photonic crystals in any frequency range.

Colloidal particle aggregation: mechanism of assembly studied via constructal theory modeling.

The assembly of colloidal particles into ordered structures is of great importance to a variety of nanoscale applications where the precise control and placement of particles is essential. A fundamental understanding of this assembly mechanism is necessary to not only predict, but also to tune the desired properties of a given system. Here, we use constructal theory to develop a theoretical model to explain this mechanism with respect to van der Waals and double layer interactions. Preliminary results show that the particle aggregation behavior depends on the initial lattice configuration and solvent properties. Ultimately, our model provides the first constructal framework for predicting the self-assembly of particles and could be expanded upon to fit a range of colloidal systems.

In situ passivation of GaAsSb nanowires for enhanced infrared photoresponse.

Surface passivation of semiconductor nanowires (NWs) is important for their optoelectronic properties and applications. Here, the in situ passivation effect of an epitaxial InP shell and the corresponding photodetector performance is experimentally studied. Compared with the unpassivated GaAs1- x Sb x core-only NWs, the GaAs1- x Sb x /InP core/shell NWs have shown much stronger photoluminescence and cathodoluminescence intensities. Correspondingly, the fabricated single GaAs1- x Sb x /InP core/shell NW photodetector shows a responsivity of 325.1 A W-1 (@ 1.3 µm and 1.5 V) that is significantly enhanced compared to that of single GaAs1- x Sb x core-only NW photodetectors (143.5 A W-1), with a comparable detectivity of 4.7 × 1010 and 5.3 × 1010 cm√Hz/W, respectively. This is ascribed to the enhanced carrier mobility and carrier concentration by the in situ passivation, which lead to both higher photoconductivity and dark-conductivity. Our results show that in situ passivation is an effective approach for performance enhancement of GaAs1-x Sb x NW based optoelectronic devices.

Review on III-V Semiconductor Single Nanowire-Based Room Temperature Infrared Photodetectors.

Recently, III-V semiconductor nanowires have been widely explored as promising candidates for high-performance photodetectors due to their one-dimensional morphology, direct and tunable bandgap, as well as unique optical and electrical properties. Here, the recent development of III-V semiconductor-based single nanowire photodetectors for infrared photodetection is reviewed and compared, including material synthesis, representative types (under different operation principles and novel concepts), and device performance, as well as their challenges and future perspectives.

Quantification of Neuropeptide Y with Picomolar Sensitivity Enabled by Guided-Mode Resonance Biosensors.

Assessing levels of neuropeptide Y (NPY) in the human body has many medical uses. Accordingly, we report the quantitative detection of NPY biomarkers applying guided-mode resonance (GMR) biosensor methodology. The label-free sensor operates in the near-infrared spectral region exhibiting distinctive resonance signatures. The interaction of NPY with bioselective molecules on the sensor surface causes spectral shifts that directly identify the binding event without additional processing. In the experiments described here, NPY antibodies are attached to the sensor surface to impart specificity during operation. For the low concentrations of NPY of interest, we apply a sandwich NPY assay in which the sensor-linked anti-NPY molecule binds with NPY that subsequently binds with anti-NPY to close the sandwich. The sandwich assay achieves a detection limit of ~0.1 pM NPY. The photonic sensor methodology applied here enables expeditious high-throughput data acquisition with high sensitivity and specificity. The entire bioreaction is recorded as a function of time, in contrast to label-based methods with single-point detection. The convenient methodology and results reported are significant, as the NPY detection range of 0.1-10 pM demonstrated is useful in important medical circumstances.

Visualization of an axion insulating state at the transition between 2 chiral quantum anomalous Hall states.

Quantum-relativistic materials often host electronic phenomena with exotic spatial distributions. In particular, quantum anomalous Hall (QAH) insulators feature topological boundary currents whose chirality is determined by the magnetization orientation. However, understanding the microscopic nature of edge vs. bulk currents has remained a challenge due to the emergence of multidomain states at the phase transitions. Here we use microwave impedance microscopy (MIM) to directly image chiral edge currents and phase transitions in a magnetic topological insulator. Our images reveal a dramatic change in the edge state structure and an unexpected microwave response at the topological phase transition between the Chern number [Formula: see text] and [Formula: see text] states, consistent with the emergence of an insulating [Formula: see text] state. The magnetic transition width is independent of film thickness, but the transition pattern is distinct in differently initiated field sweeps. This behavior suggests that the [Formula: see text] state has 2 surface states with Hall conductivities of [Formula: see text] but with opposite signs.