Tailored fabrication of a self-rolled-up AlGaN/GaN tubular structure with photoelectrochemical etching.

Group III-nitride semiconductors with tubular structures offer significant potential across various applications, including optics, electronics, and chemical sensors. However, achieving tailored fabrication of these structures remains a challenge. In this study, we present a novel, to the best of our knowledge, method to fabricate micro-sized tubular structures by rolling the layered membrane of group III-nitride alloys utilizing the photoelectrochemical (PEC) etching. To customize the geometry of the tubular structure, we conducted an analytic calculation to predict the strain and deformation for the layered membrane. Based on the calculations, we designed and fabricated an AlGaN/GaN/InGaN/n-GaN/ sapphire structure using metal-organic chemical vapor deposition (MOCVD). Photolithography and PEC etching were employed to selectively etch the sacrificial InGaN layer. We investigated the changes of optical properties of the rolled-up structure by utilizing micro-photoluminescence (µ-PL) and micro-Raman spectroscopy.

Scannable Dual-Focus Metalens with Hybrid Phase.

Metalenses with two foci in the longitudinal or transverse direction, called bifocal or dual-focus metalenses, are promising building blocks in tomography techniques, data storage, and optical tweezers. For practical applications, relative movement between the beam and specimen is required, and beam scanning is highly desirable for high-speed operation without vibration. However, dual-focus metalenses employ a hyperbolic phase that experiences off-axis aberrations, which is not suitable for beam scanning. Here, we demonstrated a scannable dual-focus metalens by employing a new phase called "hybrid phase". The hybrid phase consists of a hyperbolic phase inside and a quadratic phase outside to reduce off-axis aberrations while maintaining a high numerical aperture. We show that the two foci of the scannable dual-focus metalens move together without severe distortion for incident angles of up to 2.5°. Our design easily extends to the case of multifocusing, which is essential for various applications ranging from imaging to manipulation.

Dielectric-Engineered High-Speed, Low-Power, Highly Reliable Charge Trap Flash-Based Synaptic Device for Neuromorphic Computing beyond Inference.

The coming of the big-data era brought a need for power-efficient computing that cannot be realized in the Von Neumann architecture. Neuromorphic computing which is motivated by the human brain can greatly reduce power consumption through matrix multiplication, and a device that mimics a human synapse plays an important role. However, many synaptic devices suffer from limited linearity and symmetry without using incremental step pulse programming (ISPP). In this work, we demonstrated a charge-trap flash (CTF)-based synaptic transistor using trap-level engineered Al2O3/Ta2O5/Al2O3 gate stack for successful neuromorphic computing. This novel gate stack provided precise control of the conductance with more than 6 bits. We chose the appropriate bias for highly linear and symmetric modulation of conductance and realized it with very short (25 ns) identical pulses at low voltage, resulting in low power consumption and high reliability. Finally, we achieved high learning accuracy in the training of 60000 MNIST images.

Enhancement of Single-Photon Purity and Coherence of III-Nitride Quantum Dot with Polarization-Controlled Quasi-Resonant Excitation.

III-Nitride semiconductor-based quantum dots (QDs) play an essential role in solid-state quantum light sources because of their potential for room-temperature operation. However, undesired background emission from the surroundings deteriorates single-photon purity. Moreover, spectral diffusion causes inhomogeneous broadening and limits the applications of QDs in quantum photonic technologies. To overcome these obstacles, it is demonstrated that directly pumping carriers to the excited state of the QD reduces the number of carriers generated in the vicinities. The polarization-controlled quasi-resonant excitation is applied to InGaN QDs embedded in GaN nanowire. To analyze the different excitation mechanisms, polarization-resolved absorptions are investigated under the above-barrier bandgap, below-barrier bandgap, and quasi-resonant excitation conditions. By employing polarization-controlled quasi-resonant excitation, the linewidth is reduced from 353 to 272 µeV, and the second-order correlation value is improved from 0.470 to 0.231. Therefore, a greater single-photon purity can be obtained at higher temperatures due to decreased linewidth and background emission.

Nanowatt-Level Photoactivated Gas Sensor Based on Fully-Integrated Visible MicroLED and Plasmonic Nanomaterials.

Photoactivated gas sensors that are fully integrated with micro light-emitting diodes (µLED) have shown great potential to substitute conventional micro/nano-electromechanical (M/NEMS) gas sensors owing to their low power consumption, high mechanical stability, and mass-producibility. Previous photoactivated gas sensors mostly have utilized ultra-violet (UV) light (250-400 nm) for activating high-bandgap metal oxides, although energy conversion efficiencies of gallium nitride (GaN) LEDs are maximized in the blue range (430-470 nm). This study presents a more advanced monolithic photoactivated gas sensor based on a nanowatt-level, ultra-low-power blue (λpeak  = 435 nm) µLED platform (µLP). To promote the blue light absorbance of the sensing material, plasmonic silver (Ag) nanoparticles (NPs) are uniformly coated on porous indium oxide (In2 O3 ) thin films. By the plasmonic effect, Ag NPs absorb the blue light and spontaneously transfer excited hot electrons to the surface of In2 O3 . Consequently, high external quantum efficiency (EQE, ≈17.3%) and sensor response (ΔR/R0 (%) = 1319%) to 1 ppm NO2 gas can be achieved with a small power consumption of 63 nW. Therefore, it is highly expected to realize various practical applications of mobile gas sensors such as personal environmental monitoring devices, smart factories, farms, and home appliances.

Wide-Field Super-Resolution Optical Fluctuation Imaging through Dynamic Near-Field Speckle Illumination.

Stochastic optical fluctuation imaging (SOFI) generates super-resolution fluorescence images by emphasizing the positions of fluorescent emitters via statistical analysis of their on-and-off blinking dynamics. In SOFI with speckle illumination (S-SOFI), the diffraction-limited grain size of the far-field speckles prevents independent blinking of closely located emitters, becoming a hurdle to realize the full super-resolution granted by SOFI processing. Here, we present a surface-sensitive super-resolution technique exploiting dynamic near-field speckle illumination to bring forth the full super-resolving power of SOFI without blinking fluorophores. With our near-field S-SOFI technique, up to 2.8- and 2.3-fold enhancements in lateral spatial resolution are demonstrated with computational and experimental fluorescent test targets labeled with conventional fluorophores, respectively. Fluorescent beads separated by 175 nm are also super-resolved by near-field speckles of 150 nm grain size, promising sub-100 nm resolution with speckle patterns of much smaller grain size.

Friction Control by Deformation Mode in Nanopatterned Amorphous Carbon.

Traditionally, the manipulation of contact mechanisms has been adopted as the primary strategy to tailor the friction properties of surfaces. On the contrary, the detaching process involving the local deformation and failure at the interface has been considered relatively less important. Here, we present a new approach toward the friction control of amorphous carbon through the plasticity and resultant transition of deformation mode on nanopatterned surfaces. Depending on the topography of the nanopatterns, the mechanical responses of the surfaces alter from elastic fracture to plastic flow, through which the friction coefficient changes by a factor of 5 without manipulation of the intrinsic structure of the material.

Absent or impaired rectoanal inhibitory reflex as a diagnostic factor for high-grade (grade III-V) rectal prolapse: a retrospective study.

BACKGROUND: Clinically diagnosing high-grade (III-V) rectal prolapse might be difficult, and the prolapse can often be overlooked. Even though defecography is the significant diagnostic tool for rectal prolapse, it is noticed that rectoanal inhibitory reflex (RAIR) can be associated with rectal prolapse. This study investigated whether RAIR can be used as a diagnostic factor for rectal prolapse. METHODS: In this retrospective study, we evaluated 107 patients who underwent both anorectal manometry and defecography between July 2012 and December 2019. Rectal prolapse was classified in accordance with the Oxford Rectal Prolapse Grading System. Patients in the high-grade (III-V) rectal prolapse (high-grade group, n = 30), and patients with no rectal prolapse or low-grade (I, II) rectal prolapse (low-grade group, n = 77) were analyzed. Clinical variables, including symptoms such as fecal incontinence, feeling of prolapse, and history were collected. Symptoms were assessed using yes/no surveys answered by the patients. The manometric results were also evaluated. RESULTS: Frequencies of fecal incontinence (p = 0.002) and feeling of prolapse (p < 0.001) were significantly higher in the high-grade group. The maximum resting (77.5 vs. 96 mmHg, p = 0.011) and squeezing (128.7 vs. 165 mmHg, p = 0.010) anal pressures were significantly lower in the high-grade group. The frequency of absent or impaired RAIR was significantly higher in the high-grade group (19 cases, 63% vs. 20 cases, 26%, p < 0.001). In a multivariate analysis, the feeling of prolapse (odds ratio [OR], 23.88; 95% confidence interval [CI], 4.43-128.78; p < 0.001) and absent or impaired RAIR (OR, 5.36; 95% CI, 1.91-15.04, p = 0.001) were independent factors of high-grade (III-V) rectal prolapse. In addition, the percentage of the absent or impaired RAIR significantly increased with grading increase of rectal prolapse (p < 0.001). The sensitivity of absent or impaired RAIR as a predictor of high-grade prolapse was 63.3% and specificity 74.0%. CONCLUSIONS: Absent or impaired RAIR was a meaningful diagnostic factor of high-grade (III-V) rectal prolapse. Furthermore, the absent or impaired reflex had a positive linear trend according to the increase of rectal prolapse grading.

Correlation between Exposure to Fine Particulate Matter (PM2.5) during Pregnancy and Congenital Anomalies: Its Surgical Perspectives.

BACKGROUND: Fine particulate matter (PM2.5) can easily penetrate blood vessels and tissues through the human respiratory tract and cause various health problems. Some studies reported that particular matter (PM) exposure during pregnancy is associated with low birth weight or congenital cardiovascular anomalies. This study aimed to investigate the correlation between the degree of exposure to PM ≤ 2.5 µm (PM2.5) during pregnancy and congenital anomalies relevant to the field of pediatric surgery. METHODS: Mother-infant dyads with registered addresses in the Metropolitan City were selected during 3 years. The electronic medical records of mothers and neonates were retrospectively analyzed, with a focus on maternal age at delivery, date of delivery, gestation week, presence of diabetes mellitus (DM) or hypertension, parity, the residence of the mother and infant, infant sex, birth weight, Apgar score, and presence of congenital anomaly. The monthly PM2.5 concentration from the first month of pregnancy to the delivery was computed based on the mothers' residences. RESULTS: PM2.5 exposure concentration in the second trimester was higher in the congenital anomaly group than in the non-congenital anomaly group (24.82 ± 4.78 µg/m3, P = 0.023). PM2.5 exposure concentration did not affect the incidence of nervous, cardiovascular, and gastrointestinal anomalies. While statistically insignificant, the groups with nervous, cardiovascular, gastrointestinal, musculoskeletal, and other congenital anomalies were exposed to higher PM2.5 concentrations in the first trimester compared with their respective counterparts. The effect of PM2.5 concentration on the incidence of congenital anomalies was significant even after adjusting for the mother's age, presence of DM, hypertension, and parity. The incidence of congenital anomalies increased by 26.0% (95% confidence interval of 4.3% and 49.2%) per 7.23 µg/m3 elevation of PM2.5 interquartile range in the second trimester. CONCLUSIONS: The congenital anomaly group was exposed to a higher PM2.5 concentration in the second trimester than the non-congenital anomaly group. The PM2.5 exposure concentration level in the first trimester tended to be higher in groups with anomalies than those without anomalies. This suggests that continuous exposure to a high PM2.5 concentration during pregnancy influences the incidence of neonatal anomalies in surgical respects.

Control of the 3-Fold Symmetric Shape of Group III-Nitride Quantum Dots: Suppression of Fine-Structure Splitting.

Controlling the in-plane symmetry of wide-bandgap semiconductor quantum dots (QDs) is essential for room temperature quantum photonic applications using polarization entangled photon pairs. Herein, we report the formation of 3-fold symmetric group III-nitride QDs at the apex of a triangular pyramid via a self-limited growth mechanism. We employed the in-plane rotational symmetry of the c-plane of a Wurtzite crystal and the large built-in piezoelectric field to reduce fine-structure splitting. The QDs exhibit emission that is distinguishable from that of sidewall quantum wells, and the biexciton-exciton cascade possesses a single-photon nature. We observed the relatively low optical polarization anisotropy and small fine structure splitting under the measurement limit (270 µeV) with the 3-fold symmetric QD. In contrast with current strategies that consider group III-nitride QDs as strongly polarized single-photon emitters, our approach for controlling the QD symmetry provides a new perspective on such QDs, as polarization-entangled photon pairs.

Orthogonally Polarized, Dual-Wavelength Quantum Wire Network Emitters Embedded in Single Microrod.

Semiconductor nanowires are attractive building blocks of optoelectronics due to high efficiency and optical controllability. In particular, the mutual controllability of wavelength and polarization of light is essential for versatile applications such as displays, precise metrology, and bioimaging. We present quantum wire network emitters embedded in a single microrod capable of exhibiting orthogonally polarized dual-wavelength visible light at room temperature. The InGaN/GaN shell layers were grown on a single hexagonal GaN core microrod, spontaneously forming site-selective In-rich InGaN quantum wires on each edge between the nonpolar facets as well as each boundary between the nonpolar and semipolar facets. The orthogonally self-arranged, two sets of six quantum wires formed on the edges and the boundaries showed efficient violet and blue-green color emissions with strong linear polarization parallel and perpendicular to the c-axis at room temperature, respectively. This intriguing emission from a single microrod allows us to mutually manipulate the color and the polarization of light, which would be beneficial for photonic applications with unprecedented controllability and functionality.

Direct Transfer of Light's Orbital Angular Momentum onto a Nonresonantly Excited Polariton Superfluid.

Recently, exciton polaritons in a semiconductor microcavity were found to condense into a coherent ground state much like a Bose-Einstein condensate and a superfluid. They have become a unique testbed for generating and manipulating quantum vortices in a driven-dissipative superfluid. Here, we generate an exciton-polariton condensate with a nonresonant Laguerre-Gaussian optical beam and verify the direct transfer of light's orbital angular momentum to an exciton-polariton quantum fluid. Quantized vortices are found in spite of the large energy relaxation involved in nonresonant pumping. We identified phase singularity, density distribution, and energy eigenstates for the vortex states. Our observations confirm that nonresonant optical Laguerre-Gaussian beam can be used to manipulate chirality, topological charge, and stability of the nonequilibrium quantum fluid. These vortices are quite robust, only sensitive to the orbital angular momentum of light and not other parameters such as energy, intensity, size, or shape of the pump beam. Therefore, optical information can be transferred between the photon and exciton-polariton with ease and the technique is potentially useful to form the controllable network of multiple topological charges even in the presence of spectral randomness in a solid state system.

Optical properties of GaN nanowires grown on chemical vapor deposited-graphene.

Optical properties of GaN nanowires (NWs) grown on chemical vapor deposited-graphene transferred on an amorphous support are reported. The growth temperature was optimized to achieve a high NW density with a perfect selectivity with respect to a SiO2 surface. The growth temperature window was found to be rather narrow (815°C ± 5°C). Steady-state and time-resolved photoluminescence from GaN NWs grown on graphene was compared with the results for GaN NWs grown on conventional substrates within the same molecular beam epitaxy reactor showing a comparable optical quality for different substrates. Growth at temperatures above 820 °C led to a strong NW density reduction accompanied with a diameter narrowing. This morphology change leads to a spectral blueshift of the donor-bound exciton emission line due to either surface stress or dielectric confinement. Graphene multi-layered micro-domains were explored as a way to arrange GaN NWs in a hollow hexagonal pattern. The NWs grown on these domains show a luminescence spectral linewidth as low as 0.28 meV (close to the set-up resolution limit).

Predicting Survival of Congenital Diaphragmatic Hernia on the First Day of Life.

BACKGROUND: This study aimed to determine perinatal risk factors for 30-day mortality of congenital diaphragmatic hernia (CDH) patients and develop a prognostic index to predict 30-day mortality of CDH patients. Identifying risk factors that can prognosticate outcome is critical to obtain the best management practices for patients. METHODS: A retrospective study was performed for patients who were diagnosed with CDH from November 2000 to August 2016. A total of 10 prenatal risk factors and 14 postnatal risk factors were analyzed. All postnatal variables were measured within 24 h after birth. RESULTS: A total of 95 CDH patients were enrolled in this study, including 61 males and 34 females with mean gestational age of 38.86 ± 1.51 weeks. The overall 30-day survival rate was 63.2%. Multivariate analysis revealed that five factors (polyhydramnios, gestational age at diagnosis <25 weeks, observed-to-expected lung-to-head ratio ≤45, best oxygenation index in 24 h >11, and severity of tricuspid regurgitation ≥ mild) were independent predictors of 30-day mortality of CDH. Using these five factors, a perinatal prognostic index for 30-day mortality was developed. Four predictive models (poor, bad, good, and excellent) of the perinatal prognostic index were constructed, and external validation was performed. CONCLUSIONS: Awareness of risk factors is very important for predicting prognosis and managing patients. Five independent perinatal risk factors were identified in this study. A perinatal prognostic index was developed for 30-day mortality for patients with CDH. This index may be used to help manage CDH patients.

Self-aligned deterministic coupling of single quantum emitter to nanofocused plasmonic modes.

The quantum plasmonics field has emerged and been growing increasingly, including study of single emitter-light coupling using plasmonic system and scalable quantum plasmonic circuit. This offers opportunity for the quantum control of light with compact device footprint. However, coupling of a single emitter to highly localized plasmonic mode with nanoscale precision remains an important challenge. Today, the spatial overlap between metallic structure and single emitter mostly relies either on chance or on advanced nanopositioning control. Here, we demonstrate deterministic coupling between three-dimensionally nanofocused plasmonic modes and single quantum dots (QDs) without any positioning for single QDs. By depositing a thin silver layer on a site-controlled pyramid QD wafer, three-dimensional plasmonic nanofocusing on each QD at the pyramid apex is geometrically achieved through the silver-coated pyramid facets. Enhancement of the QD spontaneous emission rate as high as 22 ± 16 is measured for all processed QDs emitting over ∼150-meV spectral range. This approach could apply to high fabrication yield on-chip devices for wide application fields, e.g., high-efficiency light-emitting devices and quantum information processing.

How Effective is Plasmonic Enhancement of Colloidal Quantum Dots for Color-Conversion Light-Emitting Devices?

Enhancing the fluorescence intensity of colloidal quantum dots (QDs) in case of color-conversion type QD light-emitting devices (LEDs) is very significant due to the large loss of QDs and their quantum yields during fabrication processes, such as patterning and spin-coating, and can therefore improve cost-effectiveness. Understanding the enhancement process is crucial for the design of metallic nanostructure substrates for enhancing the fluorescence of colloidal QDs. In this work, improved color conversion of colloidal green and red QDs coupled with aluminum (Al) and silver (Ag) nanodisk (ND) arrays designed by in-depth systematic finite-difference time domain simulations of excitation, spontaneous emission, and quantum efficiency enhancement is reported. Calculated results of the overall photoluminescence enhancement factor in the substrate of 500 × 500 µm2 size are 2.37-fold and 2.82-fold for Al ND-green QD and Ag ND-red QD structures, respectively. Experimental results are in good agreement, showing 2.26-fold and 2.66-fold enhancements for Al ND and Ag ND structures. Possible uses of plasmonics in cases such as white LED and total color conversion for possible display applications are discussed. The theoretical treatments and experiments shown in this work are a proof of principle for future studies of plasmonic enhancement of various light-emitting materials.

Unidirectional Emission of a Site-Controlled Single Quantum Dot from a Pyramidal Structure.

Emission control of a quantum emitter made of semiconductor materials is of significance in various optical applications. Specifically, the realization of efficient quantum emitters is important because typical semiconductor quantum dots are associated with low extraction efficiency levels due to their high refractive index contrast. Here, we report bright and unidirectional emission from a site-controlled InGaN quantum dot formed on the apex of a silver-coated GaN nanopyramidal structure. We show that the majority of the extracted light from the quantum dot is guided toward the bottom of the pyramid with high directionality. We also demonstrate that nanopyramid structures can be detached from a substrate, thus demonstrating great potential of this structure in various applications. To clarify the directional radiation, the far-field radiation pattern is measured using Fourier microscopy. This scheme will pave the way toward the realization of a bright and unidirectional quantum emitter along with easy fabrication and large-area reproducibility.

Congenital adhesion band causing small bowel obstruction: What's the difference in various age groups, pediatric and adult patients?

BACKGROUND: A congenital adhesion band is a rare condition, but may induce a small bowel obstruction (SBO) at any age. However, only a few sporadic case reports exit. We aimed to identify the clinical characteristics of congenital adhesion band manifesting a SBO stratified by age group between pediatric and adult patients. METHODS: The medical records of all patients with a SBO between Jan 1, 2009 and Dec 31, 2015 were retrospectively reviewed. Cases associated with previous surgical procedure and cases of secondary obstruction due to inflammatory processes or tumor and other systemic diseases were excluded. The patients were divided into two groups according to age below or above 18 years: pediatric and adult. The basic clinical characteristics were analyzed and compared between groups. RESULTS: Of 251 patients with a SBO, 15 (5.9%) met the inclusion criteria; 10 cases in pediatric group (mean age 17.9 ± 38.7 months) and 5 cases in adult group (mean age 60.0 ± 19.7 years). The pediatric group (66.6%) included 3 neonates, 5 infants, and 2 school children. They usually presented with bilious vomiting (50.0%) and abdominal distention (60.0%), and demonstrated a high rate of early operation (80.0%) and bowel resection (70.0%). In contrast, the adult group (33.3%) presented with abdominal pain (100%) in all cases and underwent a relatively simple procedure of band release using a laparoscopic approach (60%). However, group differences did not reach statistical significance. In addition, two groups did not differ in the time interval to the operation or in the range of the operation (p = 0.089 vs. p = 0.329). No significant correlation was found between the time interval to the operation and the necessity of bowel resection (p = 0.136). There was no mortality in either group. CONCLUSIONS: Congenital adhesion band is a very rare condition with diverse clinical presentations across ages. Unlike adult patients, pediatric patients showed a high proportion of early operation and bowel resection. A good result can be expected with an early diagnosis and prompt management regardless of age.

Giant Rabi Splitting of Whispering Gallery Polaritons in GaN/InGaN Core-Shell Wire.

The hybrid nature of exciton polaritons opens up possibilities for developing a new concept nonlinear photonic device (e.g., polariton condensation, switching, and transistor) with great potential for controllability. Here, we proposed a novel type of polariton system resulting from strong coupling between a two-dimensional exciton and whispering gallery mode photon using a core-shell GaN/InGaN hexagonal wire. High quality, nonpolar InGaN multiple-quantum wells (MQWs) were conformally formed on a GaN core nanowire, which was spatially well matched with whispering gallery modes inside the wire. Both high longitudinal-transverse splitting of nonpolar MQWs and high spatial overlap with whispering gallery modes lead to unprecedented large Rabi splitting energy of ∼180 meV. This structure provides a robust polariton effect with a small footprint; thus, it could be utilized for a wide range of interesting applications.

Squeezing Photons into a Point-Like Space.

Confining photons in the smallest possible volume has long been an objective of the nanophotonics community. In this Letter, we propose and demonstrate a three-dimensional (3D) gap-plasmon antenna that enables extreme photon squeezing in a 3D fashion with a modal volume of 1.3 × 10(-7) λ(3) (∼4 × 10 × 10 nm(3)) and an intensity enhancement of 400 000. A three-dimensionally tapered 4 nm air-gap is formed at the center of a complementary nanodiabolo structure by ion-milling 100 nm-thick gold film along all three dimensions using proximal milling techniques. From a 4 nm-gap antenna, a nonlinear second-harmonic signal more than 27 000-times stronger than that from a 100 nm-gap antenna is observed. In addition, scanning cathodoluminescence images confirm unambiguous photon confinement in a resolution-limited area 20 × 20 nm(2) on top of the nano gap.