Full consideration of noise and system dynamics in numerical simulation confirmed the viability of the proposed method. Using a representative microstructured surface, the on-machine measurement points were reconstructed, with any alignment deviations calibrated, and ultimately verified by off-machine white light interferometry. Significant improvements in the efficiency and adaptability of the on-machine measurement process can be achieved by avoiding tedious operations and unique artifacts.
The development of practical surface-enhanced Raman scattering (SERS) sensing relies critically on the discovery of substrates that are simultaneously high-sensitivity, reproducible, and low-cost. This paper reports on a straightforward SERS substrate design, incorporating a metal-insulator-metal (MIM) structure of silver nanoislands (AgNI), a silica (SiO2) layer, and a silver film (AgF). Using only evaporation and sputtering processes, the substrates are fabricated; these methods are simple, fast, and low-cost. The proposed SERS substrate, leveraging the combined effects of hotspots and enhanced interference within the AgNIs structure and the plasmonic cavity between AgNIs and AgF, exhibits an enhancement factor (EF) of 183108, allowing for a limit of detection (LOD) down to 10⁻¹⁷ mol/L for rhodamine 6G (R6G) molecules. Conventional active galactic nuclei (AGN) lacking metal-ion-migration (MIM) structure display enhancement factors (EFs) 18 times lower than the EFs observed in the studied cases. Substantial reproducibility is a hallmark of the MIM structure, as evidenced by its relative standard deviation (RSD) that remains below 9%. Through the application of evaporation and sputtering techniques alone, the proposed SERS substrate is fabricated, with no reliance on conventional lithographic methods or chemical synthesis. Ultrasensitive and reproducible SERS substrates, easily fabricated via this method, are presented in this work, promising significant applications in developing various biochemical sensors using SERS.
Sub-wavelength artificial electromagnetic structures, known as metasurfaces, are capable of resonating with the electric and magnetic fields of incident light. This facilitates light-matter interaction, showcasing immense potential and application value in sensing, imaging, and photoelectric detection. Far too many current metasurface-enhanced ultraviolet detectors rely on metal metasurfaces, leading to substantial ohmic losses. The application of all-dielectric metasurfaces in this field remains comparatively understudied. Employing theoretical design and numerical simulation, researchers analyzed the multilayer structure composed of a diamond metasurface, a gallium oxide active layer, a silica insulating layer, and an aluminum reflective layer. At a gallium oxide thickness of 20 nanometers, the absorption rate surpasses 95% within the 200-220nm operational wavelength range. Further, alteration of structural parameters permits adjustment of the working wavelength. The proposed structure's design incorporates characteristics resistant to polarization and variations in incident angle. Significant promise for this work resides in ultraviolet detection, imaging, and communication technologies.
The recently discovered optical metamaterials known as quantized nanolaminates. So far, atomic layer deposition and ion beam sputtering have proven their feasibility. This paper describes the successful magnetron sputtering process used to deposit quantized nanolaminates based on alternating Ta2O5 and SiO2 layers. The deposition procedure, outcomes, and material characterization of films produced across a broad parameter spectrum will be detailed. In addition, we will exemplify the use of magnetron-sputtered quantized nanolaminates in creating optical interference coatings, including antireflection and mirror coatings.
Among the rotationally symmetric periodic (RSP) waveguides are a fiber grating and a one-dimensional (1D) periodic array of spheres. Bound states in the continuum (BICs) are known to occur in lossless dielectric RSP waveguides, a well-established principle. The Bloch wavenumber, the frequency, and the azimuthal index m define a guided mode's characteristics within an RSP waveguide. A BIC's guided mode, dictated by a specific m-value, permits unrestricted cylindrical wave propagation into, or out from, the surrounding homogeneous medium to infinity. In the context of lossless dielectric RSP waveguides, this paper investigates the robustness of non-degenerate BICs. Is a BIC, initially situated within an RSP waveguide with a z-axis reflection symmetry and periodicity, capable of enduring slight, arbitrary structural perturbations to the waveguide, as long as the waveguide's periodicity and z-axis reflection symmetry are preserved? learn more The research shows that when m is zero and m is zero, generic BICs with only one propagating diffraction order are robust and non-robust, respectively, and a non-robust BIC with m equal to zero can continue to exist in the presence of a perturbation that includes only one tunable parameter. 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. The theory's validity is numerically shown for BICs propagating with m=0 and =0 through fiber gratings and 1D arrays of circular disks.
In electron and synchrotron X-ray microscopy, ptychography, a lens-free coherent diffractive imaging method, is currently in extensive use. In its near-field execution, it provides a route to quantitatively imaging phases, with accuracy and resolution that is competitive with holographic techniques, while expanding the imaging scope and enabling the automatic removal of the illumination beam profile from the sample image. This paper introduces the integration of near-field ptychography and a multi-slice model, demonstrating a novel capacity to retrieve high-resolution phase images of samples whose thickness surpasses the depth of field of alternative imaging methodologies.
The study focused on deciphering the mechanisms of carrier localization center (CLC) generation in Ga070In030N/GaN quantum wells (QWs) and evaluating their impact on the performance parameters of the devices. We concentrated our efforts on the influence of native defects introduced into the QWs as a principal element in understanding the mechanism for the production of CLC. Two examples of GaInN-based LEDs were made, one with and the other without pre-trimethylindium (TMIn) flow-treated quantum wells, for this task. The QWs underwent a pre-TMIn flow treatment, a process designed to regulate the inclusion of defects and impurities. Employing steady-state photo-capacitance, photo-assisted capacitance-voltage measurements, and high-resolution micro-charge-coupled device imaging, we sought to determine the effect of pre-TMIn flow treatment on native defect incorporation into QWs. The experimental results indicated a significant relationship between the generation of CLCs in QWs during growth and native defects, principally VN-related defects/complexes, attributed to their strong attraction to indium atoms and the clustering mechanisms. Subsequently, the construction of CLC structures is profoundly damaging to the performance of yellow-red QWs, by concurrently raising the non-radiative recombination rate, lowering the radiative recombination rate, and increasing the operating voltage—a difference from blue QWs.
Using a p-Si (111) substrate and direct growth of an InGaN bulk active region, a red nanowire LED has been developed and demonstrated. The LED's wavelength stability is notably good upon increasing the injection current and narrowing the linewidth, negating the presence of a quantum confined Stark effect. Efficiency diminishes when injection current reaches relatively high levels. The output power is measured at 0.55mW and external quantum efficiency at 14% at 20mA (20 A/cm2) and a peak wavelength of 640nm; at 70mA, this value increases to 23% with a peak wavelength shifted to 625nm. Operation of the p-Si substrate exhibits a high level of carrier injection currents due to a naturally occurring tunnel junction at the n-GaN/p-Si interface, thus making it a prime candidate for device integration.
Microscopy and quantum communication utilize light beams with Orbital Angular Momentum (OAM), mirroring the resurgence of the Talbot effect in atomic systems and x-ray phase contrast interferometry. Within the near-field of a binary amplitude fork-grating, the Talbot effect enables the observation of an OAM carrying THz beam's topological charge, which we show to remain consistent over multiple fundamental Talbot lengths. breast microbiome Behind the fork grating, we study and quantify the diffracted beam's Fourier-domain power distribution evolution to recover the typical donut form, finally comparing the experimental results with theoretical simulations. Integrated Chinese and western medicine Employing the Fourier phase retrieval technique, we identify the inherent phase vortex. For a more comprehensive analysis, we ascertain the OAM diffraction orders of a fork grating situated in the far-field using a cylindrical lens.
A steady increase in the application complexity handled by photonic integrated circuits results in a corresponding increase in the challenges faced by individual component functionality, performance, and footprint. Employing fully automated design procedures, inverse design methodologies have recently displayed significant potential in fulfilling these requirements, revealing novel device configurations that go beyond the boundaries of conventional nanophotonic design principles. A dynamic binarization approach is introduced for the objective-primary algorithm, which is the foundation of the most successful inverse design algorithms currently in use. Our results demonstrate a significant advantage in performance for objective-first algorithms when compared to previous implementations, with validation provided by both simulations and experimental measurements on fabricated TE00 to TE20 waveguide mode converters.