Numerical simulation, which thoroughly considered noise and system dynamics, validated the proposed method's feasibility. In the case of a standard microstructured surface, measured points from the on-machine process were reconstructed after alignment deviation calibration, which was then validated by off-machine white light interferometry. Simplifying the on-machine measurement process, by removing tedious operations and unique artifacts, considerably improves its efficiency and flexibility.
The pursuit of practical surface-enhanced Raman scattering (SERS) applications has been challenged by the lack of substrates that provide a combination of high sensitivity, reproducibility, and low cost. In this study, we present a straightforward surface-enhanced Raman scattering (SERS) substrate, comprising a metal-insulator-metal (MIM) configuration of silver nanoisland (AgNI) – silica (SiO2) – silver film (AgF). The fabrication of the substrates relies entirely on evaporation and sputtering processes, which are simple, fast, and low-cost procedures. Through the integration of hotspot amplification and interference phenomena within AgNIs, coupled with a plasmonic cavity formed between AgNIs and AgF, the proposed SERS substrate achieves an enhancement factor (EF) of 183108, enabling a detection limit (LOD) as low as 10⁻¹⁷ mol/L for rhodamine 6G (R6G) molecules. Active galactic nuclei (AGN) without metal-ion-migration (MIM) structures exhibit enhancement factors (EFs) that are 18 times lower than those of the EFs in the present case. In conjunction with other factors, the MIM structure reveals remarkable reproducibility with a relative standard deviation (RSD) below 9%. Only evaporation and sputtering methods are employed in the fabrication of the proposed SERS substrate, thereby dispensing with conventional lithography and chemical synthesis. The fabrication of ultrasensitive and reproducible SERS substrates, as detailed in this work, holds significant potential for the development of diverse SERS-based biochemical sensors.
Exhibiting resonance with the electric and magnetic fields of incident light, the metasurface—an artificial electromagnetic structure smaller than the light's wavelength—promotes light-matter interaction. Its considerable application potential lies in fields like sensing, imaging, and photoelectric detection. A significant portion of previously reported metasurface-enhanced ultraviolet detectors leverage metallic metasurfaces, which are plagued by ohmic losses. Consequently, the exploration of all-dielectric metasurfaces for this application is relatively limited. Through theoretical design and numerical simulation, a multilayer structure was meticulously developed, featuring a diamond metasurface, gallium oxide active layer, silica insulating layer, and an aluminum reflective layer. When the gallium oxide thickness reaches 20 nanometers, absorption surpasses 95% at the 200-220nm working wavelength. Moreover, the operational wavelength is tunable via adjustment of structural parameters. The proposed structure demonstrates a lack of dependence on polarization and incidence angle. The fields of ultraviolet detection, imaging, and communications hold substantial promise for this work.
Quantized nanolaminates, a relatively new discovery, are a subcategory of optical metamaterials. Atomic layer deposition and ion beam sputtering have, to date, showcased the feasibility of these methods. This paper describes the successful magnetron sputtering process used to deposit quantized nanolaminates based on alternating Ta2O5 and SiO2 layers. A comprehensive analysis encompassing the deposition process, experimental results, and material characterization of films across a broad array of parameters will be presented. Beyond that, the use of magnetron sputtered quantized nanolaminates in optical interference coatings, such as anti-reflective and mirror coatings, will be shown.
A one-dimensional (1D) periodic array of spheres and a fiber grating demonstrate the concept of rotationally symmetric periodic (RSP) waveguides. Lossless dielectric RSP waveguides are known to host bound states in the continuum (BICs), a well-recognized phenomenon. The frequency, Bloch wavenumber, and azimuthal index m, collectively, specify any guided mode present in an RSP waveguide. Cylindrical waves, confined to a BIC's guided mode with a fixed m-value, can propagate indefinitely within the encompassing homogeneous medium, going towards or away from it. We analyze the robustness of non-degenerate BICs, operating within lossless dielectric RSP waveguides, in this study. Can the existence of a BIC within an RSP waveguide, possessing reflection symmetry along its z-axis and periodicity, be sustained when the waveguide encounters slight, but arbitrary, structural perturbations, which maintain the waveguide's periodicity and z-axis reflection symmetry? genetic information The findings demonstrate that for m equal to zero and m equal to zero, generic BICs featuring a single propagating diffraction order are robust and non-robust, respectively, and a non-robust BIC with m equaling zero may persist even if the perturbation has only a single tunable factor. Employing mathematical rigor, the existence of a BIC in a perturbed structural framework, where the perturbation remains both small and arbitrary, validates the theory. This framework includes an extra tunable parameter for the case of m equaling zero. BIC propagation, with m=0 and =0, in fiber gratings and 1D arrays of circular disks, is demonstrated by numerical examples supporting the theory.
Within electron and synchrotron-based X-ray microscopy, the lens-free coherent diffractive imaging method, ptychography, is extensively employed. Through its near-field operation, the technology allows for quantitative phase imaging, an approach that achieves accuracy and resolution comparable to holography, supplemented by broader field visibility and the automatic removal of illumination beam artifacts from the sample's image. Our paper details the integration of near-field ptychography with a multi-slice model, uniquely enabling the recovery of high-resolution phase images for specimens whose thickness extends beyond the depth of field accessible to alternative approaches.
This research was designed to improve our understanding of the mechanisms that lead to the development of carrier localization centers (CLCs) in Ga070In030N/GaN quantum wells (QWs), along with evaluating their consequences for device performance. A significant aspect of our research was investigating the presence of native defects integrated within the QWs to comprehend the mechanism driving CLC development. To achieve this objective, we crafted two GaInN-based LED samples, one with pre-trimethylindium (TMIn) flow-treated quantum wells and the other without. To regulate the entry of defects and impurities into the QWs, a pre-TMIn flow treatment was applied. Through the application of steady-state photo-capacitance, photo-assisted capacitance-voltage measurements, and high-resolution micro-charge-coupled device imaging, we examined the effects of pre-TMIn flow treatment on the incorporation of native defects into the QWs. The experimental results highlighted a strong connection between CLC generation in QWs during growth and native defects, mainly VN-related, as a result of their strong affinity for In atoms and the inherent nature of their clustering. Additionally, the formation of CLC structures proves detrimental to the performance of yellow-red QWs, because they simultaneously increase the non-radiative recombination rate, reduce the radiative recombination rate, and increase the operating voltage, contrasting with the behavior of blue QWs.
A p-Si (111) substrate is employed to directly grow an InGaN bulk active region for the creation of a demonstrated red nanowire LED. An increase in the injection current and a decrease in the linewidth contribute to the LED exhibiting a relatively good degree of wavelength stability, unaffected by a quantum confined Stark effect. High injection currents are associated with a noticeable reduction in operational efficiency. At 20mA (20 A/cm2), the output power measured is 0.55mW, while the external quantum efficiency reaches 14% at a peak wavelength of 640nm; at 70mA, the efficiency ascends to 23% with a peak wavelength of 625nm. Operation on the p-Si substrate exhibits considerable carrier injection currents originating from the naturally formed tunnel junction at the n-GaN/p-Si interface, rendering it well-suited for device integration.
Exploring Orbital Angular Momentum (OAM) light beams in applications spans from microscopy to quantum communication, paralleling the reappearance of the Talbot effect in applications like atomic systems and x-ray phase contrast interferometry. Employing the Talbot effect, we demonstrate the topological charge of a THz beam carrying orbital angular momentum (OAM) in the near-field of a binary amplitude fork-grating, showcasing its persistence through several fundamental Talbot lengths. epigenetic biomarkers To ascertain the characteristic donut-shaped power distribution of the diffracted beam behind the fork grating, we measure and analyze its evolution in the Fourier domain, subsequently comparing the experimental findings to corresponding simulations. Opevesostat The Fourier phase retrieval method allows us to isolate the inherent phase vortex. To enhance the analysis, we evaluate the OAM diffraction orders of a fork grating in the far-field, employing a cylindrical lens.
The progressive complexity of applications tackled by photonic integrated circuits places greater demands on the capabilities, performance, and size of individual components. Inverse design methods, with their fully automated design procedures, have demonstrably shown great potential in addressing these requirements by enabling access to non-conventional device layouts that transcend established nanophotonic design principles. This work details a dynamic binarization method for the objective-first algorithm, the driving force behind the most successful inverse design algorithms currently. By employing objective-first algorithms, we achieve notable performance improvements over previous approaches. This is highlighted by our results for a TE00 to TE20 waveguide mode converter, both in simulations and in experiments involving fabricated devices.