All-Dielectric Gratings with High-Quality Structural Colors.

We present a dual-layer hafnium dioxide (HfO2) grating capable of full-color modulation in the visible spectrum by leveraging the magnetic dipole resonance induced by the lower-layer HfO2 grating, while the upper-layer HfO2 grating serves as a refractive index matching layer to effectively suppress high-order Mie resonances at shorter wavelengths. The HfO2/HfO2 grating exhibits a significantly larger distribution area in the CIE 1931 chromaticity diagram compared to the HfO2 grating. Furthermore, the structural color saturation closely approximates that of monochromatic light. Under varying background refractive index environments, this structure consistently exhibits high-quality structural color. However, the hue of the structural color undergoes alterations. When the polarization angle is below 20°, the saturation of the acquired structural color remains remarkably consistent. However, exceeding 20° results in a significant degradation in the quality of the structural color. This study demonstrates the promising potential for diverse applications, encompassing fields such as imaging and displays.

Investigation of perfect narrow-band absorber in silicon nano hole array.

In this paper, we proposed a triple layer structure consisting of the bottom silver layer, thin silicon oxide space layer, and ultrathin semiconductor silicon film with nano hole array achieving three absorption peaks with narrow band. The absorption spectrum can be easily controlled by adjusting the structural parameters including the radius and period of the nano hole array, and the maximal absorption can reach 99.0% and the narrowest full width of half maximum can reach about 6.5 nm in theory. We also clarified the physical mechanism of the proposed structure in details by finite-difference time-domain simulation, in which the three narrow band perfect adsorption peaks can be attributed to electric dipole resonance, magnetic dipole resonance and plasmonic resonance respectively. At the same time, we used a low-cost nanosphere lithography method to fabricate the proposed nano hole array in large area. In experiment, the absorption peak of the proposed triple layer structure can reach up to 98.3% and the narrowest full width of half maximum can reach up to about 10.1 nm. The highest quality factor Q can reach up to 98.4. This work can open a new avenue for high-quality factor narrow band perfect absorption using ultrathin semiconductor film and benefit for many fields such as infrared sensors, plasmonic filters, and hyperspectral imaging.

Paracondylar process combined with persistent first intersegmental vertebral artery: an anatomic case report and literature review.

The paracondylar process (PCP) and the persistent first intersegmental vertebral artery (PFIA) are both rare variations at the craniovertebral junction. We report the above two variations coexisting in one cadaveric head during the training of far lateral approach in our skull base lab. The specimen simultaneously had a left occipitalized atlas associated with a PFIA and a right PCP. The previous reports, the embryogenesis, and the clinical implications of the two variations were also reviewed. Preoperative recognition of the rare variations is essential to a safe far lateral approach.

An Omnidirectional Dual-Functional Metasurface with Ultrathin Thickness.

Although metasurfaces have received enormous attention and are widely applied in various fields, the realization of multiple functions using a single metasurface is still rarely reported to date. In this work, we propose a novel dual-functional metasurface that can be applied as a mid-infrared narrowband thermal light source in optical gas sensing and a long-wave infrared broadband absorber in photodetection. By actively tailoring the structure and constituent materials of the metasurface, the device yields an absorptivity of over 90% from 8 µm to 14 µm, while it exhibits an emissivity of 97.4% at the center wavelength of 3.56 µm with a full width at half-maximum of 0.41 µm. Notably, the metasurface is insensitive to the incident angle under both TM- and TE-polarized light. The proposed dual-functional metasurface possesses many advantages, including a simple structure, thin thickness, angle and polarization insensitivity, and compatibility with optical devices, which are expected to simplify the existing imaging systems and improve the performance of photodetection equipment.

Multi-layered all-dielectric grating visible color filter with a narrow band and high-quality factor.

In this paper, we proposed a double-layer all-dielectric grating. Under the premise of ensuring the strength of the resonance peak, the upper SiO2 grating layer suppresses the tendency of high-order dipole resonance excitation and improves the transmittance at the non-resonant position (T > 99%). The distribution of chromaticity coordinates on the CIE 1931 chromaticity diagram also proves that suppressing side peaks can effectively increase the saturation of structural colors, which is essential for a high precision imaging system. The cyclic displacement current excites the magnetic dipole resonance, which causes the magnetic field to be confined in the high refractive index material HfO2 grating layer. By adjusting the duty cycle of the grating structure, a reflection spectrum with low full width half maximum (FWHM) (∼2 nm) and high-quality factor Q (∼424.5 nm) can be obtained. And the spectral intensity is more sensitive to the polarization angle. This work is of great significance to the development of sensors, display imaging and other fields. At the same time, the material of the grating filter meets the requirements of high damage threshold of the high-power laser system, and its high-power laser application potential is inestimable.

Near-infrared narrow-band minus filter based on a Mie magnetic dipole resonance.

The traditional minus filter is composed of many layers of thin films, which makes it difficult and complicated to manufacture. It is sensitive to incident light angle and polarization. Here, we propose a near-infrared narrow-band minus filter with a full width at half maximum around 5 nm made of all-dielectric Si-SiO2 structures without any ohmic loss. The stop band transmittance of the proposed filter is close to 0, while its broad pass band transmittance is as high as 90% in the work wavelength range. Theoretical analysis shows that the transmission dip originated from magnetic dipole resonance: Its position can be tuned from 1.3 µm to 1.8 µm by changing the thickness of Si structure, and the proposed structure is insensitive to changes in incident light angle and polarization angle. We further studied its potential applications as a refractive index sensor. The sensitivity of dip1 and dip2 are as high as 953.53 nm/RIU and 691.09 nm/RIU, while their figure of merit is almost unchanged: 59.59 and 115.18, respectively.

Predicting Neurological Deterioration after Moderate Traumatic Brain Injury: Development and Validation of a Prediction Model Based on Data Collected on Admission.

Moderate traumatic brain injury (mTBI) is a heterogeneous entity that is poorly defined in the literature. Patients with mTBI have a high rate of neurological deterioration (ND), which is usually accompanied by poor prognosis and no definitive methods to predict. The purpose of this study is to develop and validate a prediction model that estimates the ND risk in patients with mTBI using data collected on admission. Data for 479 patients with mTBI collected retrospectively in our department were analyzed by logistic regression models. Bivariable logistic regression identified variables with a p < 0.05. Multi-variable logistic regression modeling with backward stepwise elimination was used to determine reduced parameters and establish a prediction model. The discrimination efficacy, calibration efficacy, and clinical utility of the prediction model were evaluated. The prediction model was validated using data for 176 patients collected from another hospital. Eight independent prognostic factors were identified: hypertension, Marshall scale (types III and IV), subdural hemorrhage (SDH), location of contusion (frontal and temporal contusions), Injury Severity Score >13, D-dimer level >11.4 mg/L, Glasgow Coma Scale score ≤10, and platelet count ≤152 × 109/L. A prediction model was established and was shown as a nomogram. Using bootstrapping, internal validation showed that the C-statistic of the prediction model was 0.881 (95% confidence interval [CI]: 0.849-0.909). The results of external validation showed that the nomogram could predict ND with an area under the curve of 0.827 (95% CI: 0.763-0.880). The present model, based on simple parameters collected on admission, can predict the risk of ND in patients with mTBI accurately. The high discriminative ability indicates the potential of this model for classifying patients with mTBI according to ND risk.

Linewidth reduction effect of a cavity-coupled dual-passband plasmonic filter.

We propose a novel cavity-coupled MIM nano-hole array structure that exhibits a tunable dual passband in the near-infrared regime. When compared with the traditional single metal film, the designed structure provides a coupling effect between Gspp and SPP to significantly reduce the linewidths of the two transmission peaks. We also reveal the physical origin of the positive and negative influence of the cavity effect on the transmission of high-frequency and low-frequency peaks. This work supplies a new modulation theory for plasmonic devices based on the EOT phenomenon and has a wide application prospect in the fields of infrared sensor, plasmonic filter, and hyperspectral imaging.

Cavity-driven hybrid plasmonic ultra-narrow bandpass filter.

We propose a novel compound grating structure that exhibits a tunable ultra-narrowband transmission in the near infrared regime. The thin microstructure can realize a steep wave form through a Fano-like resonance by coupling different propagation-type SPP modes and with a narrow line width formed by the energy band gap. Additionally, the out-of-band suppression is remarkably enhanced. It effectively solves the constraint relationship between high transmittance, narrow line width, and weak side peak of the plasmonic filter, and the structure is suitable for integration with detectors in the near infrared regime.

Structurally tunable plasmonic absorption bands in a self-assembled nano-hole array.

In this paper, we demonstrate a theoretical and experimental study on a nano-hole array that can realize perfect absorption in the visible and near-infrared regions. The absorption spectrum can be easily controlled by adjusting the structural parameters including the radius and period of the nano-hole, and the maximal absorption can reach 99.0% in theory. In order to clarify the physical mechanism of the absorber, we start from the extraordinary optical transmission supported by the nano-hole array in a thin metallic film coated on a glass substrate, and then analyse the perfect absorption in the metal-insulator-metal structure. The surface plasmon modes supported by the nano-hole array are completely clarified and both the FDTD simulation and waveguide theory are used to help us understand the physical mechanism, which can provide a new perspective in designing this kind of perfect absorber. In addition, the nano-hole array can be fabricated by simple and low-cost nanosphere lithography, which makes it a more appropriate candidate for spectroscopy, photovoltaics, photodetectors, sensing, and surface enhanced Raman scattering.

Microcavity electrodynamics of hybrid surface plasmon polariton modes in high-quality multilayer trench gratings.

In common plasmonic structures, absorption and radiation losses are often mutually restricted and can seriously influence the device performance. The current study presents a compound structure composed of multilayer grating stripes and multilayer shallow trenches. A small depth was adopted for the trench configuration to exclude the extra bend loss. These two sections supported Fabry-Perot resonance and cavity modes, respectively, with hybrid modes formed through intercoupling. In addition, the total loss for the entire framework was clearly reduced due to the introduction of the trench geometry, indicating that both absorption and radiation losses were successfully taken into consideration in the compound structure. Significantly, such a low loss realized by the hybridization of surface plasmon polariton modes has rarely been seen before. Moreover, the debatable relationship between the total and partial quality factors was described for the first time based on a hybrid mode analysis to establish a new approach to investigate the different resonance modes. In the detailed calculation process, the relative electric field intensity was first adopted to stipulate the effective areas for the various modes, which is more reasonable than using the common definition that is based on a unit structure. The multilayer trench grating exhibited a relatively low loss without weakening energy localization, which is significant in the design of plasmonic devices.

Large area and broadband ultra-black absorber using microstructured aluminum doped silicon films.

A large area and broadband ultra-black absorber based on microstructured aluminum (Al) doped silicon (Si) films prepared by a low-cost but very effective approach is presented. The average absorption of the absorber is greater than 99% within the wide range from 350 nm to 2000 nm, and its size reaches to 6 inches. We investigate the fabrication mechanism of the absorber and find that the Al atom doped in silicon improves the formation of the nanocone-like microstructures on the film surface, resulting in a significant decrease in the reflection of incident light. The absorption mechanism is further discussed by experiments and simulated calculations in detail. The results show that the doped Al atoms and Mie resonance formed in the microstructures contribute the broadband super-high absorption.

Silicon-based multilayer gratings with a designable narrowband absorption in the short-wave infrared.

We demonstrate an Al/Si multilayer-grating microstructure covered on Si substrate. This microstructure presents a designable narrowband absorption in short-wave infrared (SWIR) waveband (2.0 µm-2.3 µm). We investigate its absorption mechanism by both modeling and simulations, and explain the results well with metal-insulator-metal and Fabry-Perot cavity theory. Furthermore, we present the absorption of fabricated multilayer-grating microstructure through experiment, and discuss the influence of structure's lateral angle on its absorption in detail. This work provides the possibility to design Si-based devices with designable working bands in SWIR spectrum.

Novel aluminum plasmonic absorber enhanced by extraordinary optical transmission.

We report a theoretical and experimental study on a novel type of aluminum super absorber which exhibits a near perfect absorption based on the surface plasmon resonance in the visible and near-infrared spectrum. The absorber consists of Ag/SiO2/Al triple layers in which the top Al layer is patterned by a periodic nano hole array. The absorption spectrum can be easily controlled by adjusting the structure parameters including the radius of the nano hole and the maximal absorption can reach 99.0% in theory. We completely analyze the SPP and LSP modes supported by the metal-dielectric-metal structure and their contribution to the ultrahigh absorption. On this basis, we find a novel method to enhance the absorption via the simultaneous excitation of SPP at different interfaces theoretically and experimentally. Moreover, for the first time we clarify the EOT caused by the nano hole array can enhance the absorption by experiment, which is not reported in previous works. This kind of absorber can be fabricated by low-cost colloidal sphere lithography and the use of stable Al overcomes the disadvantages brought by the noble metal, which make it a more appropriate candidate for photovoltaics, spectroscopy, photodetectors, sensing, and surface enhanced Raman scattering.

Compensating the Degradation of Near-Infrared Absorption of Black Silicon Caused by Thermal Annealing.

We propose the use of thin Ag film deposition to remedy the degradation of near-infrared (NIR) absorption of black Si caused by high-temperature thermal annealing. A large amount of random and irregular Ag nanoparticles are formed on the microstructural surface of black Si after Ag film deposition, which compensates the degradation of NIR absorption of black Si caused by thermal annealing. The formation of Ag nanoparticles and their contributions to NIR absorption of black Si are discussed in detail.

Roughness reduction of large-area high-quality thick Al films for echelle gratings by multi-step deposition method.

Generally, echelle grating ruling is performed on a thick Al film. Consequently, high-quality large-area thick Al films preparation becomes one of the most important factors to realize a high-performance large-size echelle grating. In this paper, we propose a novel multi-step deposition process to improve thick Al films quality. Compared with the traditional single-step deposition process, it is found that the multi-step deposition process can effectively suppress large-size grains growth resulting in a low surface roughness and high internal compactness of thick Al films. The differences between single- and multi-step deposition processes are discussed in detail. By using multi-step deposition process, we prepared high-quality large-area Al films with a thickness more than 10 µm on a 520 mm × 420 mm neoceramic glass substrate.

Surface plasmon enhanced organic solar cells with a MoO3 buffer layer.

High-efficiency surface plasmon enhanced 1,1-bis-(4-bis(4-methyl-phenyl)-amino-phenyl)-cyclohexane:C70 small molecular bulk heterojunction organic solar cells with a MoO3 anode buffer layer have been demonstrated. The optimized device based on thermal evaporated Ag nanoparticles (NPs) shows a power conversion efficiency of 5.42%, which is 17% higher than the reference device. The improvement is attributed to both the enhanced conductivity and increased absorption due to the near-field enhancement of the localized surface plasmon resonance of Ag NPs.