Optical Review最新文献

In this paper, a 1550 nm subwavelength triangular prism silver nanowire SPPs hybrid waveguide structure with dual coupling modes was proposed. By introducing two mode coupling regions, the waveguide has achieved efficient and strong mode coupling, which endows the hybrid waveguide with the characteristics of a small effective mode area, a long transmission length and good robustness. The effective mode area of the proposed waveguide is less than 0.002, and the transmission length reaches over 300 μm, which has great application value in the design of small optoelectronic devices.

Actual network typically has different node dynamics, uncertainties, and delay effects. Therefore, when studying the synchronization between laser networks, fully considering these practical situations has important practical value. In this work, we not only consider the delay effect of connections between laser network nodes, but also assume the existence of uncertain parameter and different dynamics of network nodes. Therefore, uncertain parameter in the laser network is identified through the designed parameter identification law. Meanwhile, we design a suitable Lyapunov–Krasovskii functional to obtain the synchronization criterion between laser networks. Finally, we verify the main results of the theoretical analysis through numerical simulations, and find that they are completely consistent.

Self-referential holography (SRH), a holographic technique that enables the recording, reading, and control of two-dimensional (2D) patterns using a one-beam geometry, can be applied to holographic data storage (HDS) and optoelectronic deep neural network (OE-DNN). Since both applications are implemented using the same optical system, they can be integrated into a single system. We propose a self-referential HDS (SR-HDS) with a built-in denoising function using a self-referential holographic deep neural network (SR-HDNN), where the quality of reconstructed datapages in HDS can be enhanced using deep neural networks (DNNs) without requiring costly electronic computers for implementation. Numerical simulations are performed to demonstrate the feasibility of the proposed method.

Optical non-contact 3D shape measurement has attracted wide attention from the scientific community. Although by increasing the frequency of projected fringes, the measurement accuracy can be improved, difficulties in phase unwrapping are induced. Reducing the number of projected fringes can also increase the measurement speed. However, there are still certain challenges to meeting the requirements of high speed and high precision without creating additional projection fringe patterns. Along these lines, an improved 3D shape measurement method based on Fourier transform profilometry and phase coding was proposed in this work, where only four projection fringe patterns must be projected. A sinusoidal grating and a uniform gray-level pattern were used to obtain the wrapped phase recovered by the background-normalized Fourier transform algorithm. Two captured phase coding patterns combine with the uniform gray-level pattern to obtain fringe orders solved by the 2 + 1 phase-shifting algorithm. After the fringe order is calculated, the absolute phase map is retrieved and the 3D shape can be obtained. The proposed method is suitable for isolated and complex objects. The performance of the proposed method in reconstructing the 3D shapes of objects was experimentally verified.

In the age of the Internet of Things, physical security framework of edge devices connected to the Internet is essential. Accordingly, higher security and higher authenticity are strongly required to prevent unauthorized invasion via irregular devices. On the other hand, artifacts comprising nano-scale structures that are smaller than the fabrication resolutions of general technologies are technically difficult to duplicate. Thus, the addition of such artifacts to each edge device or its components can be considered to ensure security and authenticity because the nano-scale artifact metrics are self-defined based on their higher clone resistance. However, reading out and evaluating physical identities of such artifacts requires the use of advanced setups and techniques. Therefore, they are not preferred in widespread practical applications. In this study, we propose and demonstrate an optical approach as another readout method for nano-scale physical identity based on a simpler setup and technology. Furthermore, the performance of experimental authentication using the identity of nano-scale artifacts was quantitatively verified. Our experimental setup operates by following a white light interferometry sensing. Generally, white light interferometry aids in obtaining numerous interference images by changing the distance between the target and the detection setup precisely to reconstruct a height distribution image with nano-scale resolution. However, in our application, reconstruction of the height distribution image is not necessarily required, while a single interference image is expected to be defined as identity of the target artifact. Subsequently, certain interference images were used to calculate the false match and non-match rates to qualitatively evaluate the authentication performance of the proposed method. Furthermore, the dependence of the performance on the spatial resolution and corresponding data size of the interference images was experimentally investigated. The results of these experiments pave the way for a practical and reliable method for the physical security of nano-scale artifacts based on general optical technology.

An optical setup using three laser sources with different wavelengths was proposed for the formation of a holographic memory consisting of volumetric periodic structures using liquid–crystal composites. Structural analysis of the holographic gratings formed at different wavelengths was performed using polarizing optical microscopy and scanning electron microscopy. The periodic interval between the interference fringes and the volumetric periodic structures decreased with a decrease in the wavelength of the laser used in the fabrication process. The fabricated holographic memory can be used to record and reconstruct circuit information in optically reconfigurable gate arrays (ORGAs) by applying parallel processing techniques based on spatial light wiring. The development of interference exposure optical systems for various laser wavelengths, including blue lasers with short wavelengths, is extremely important for improving the capacity of holographic memory by miniaturizing its internal lattice structure. The fabricated holographic memory demonstrated the ability to accurately record and reconstruct circuit information patterns by switching between different laser wavelengths. Establishing a holographic memory system for ORGAs is essential for developing radiation-resistant devices that can be used in fields requiring high reliability.

A thin-form-factor laser scanning system composed of a planar-type laser source with a waveguide-type combiner and a micro-electromechanical systems (MEMS) scanning mirror was developed. The laser source and MEMS mirror were mounted on a common substrate, resulting in a thin and small form factor. The scanning laser beam comprised coaxially combined red, green, and blue beams, capable of projecting a full-color laser scanning image. The system design incorporated a projection image distortion analysis, which assumed a raster scan scheme, whereby the horizontal fast-scan direction lay in the plane defined by the incident beam direction and the direction normal to the common substrate, and the vertical slow-scan direction lay in a plane perpendicular to the horizontal scan plane. The incident angle of the laser beam on the MEMS mirror was kept small (less than 45°). Three types of laser scanning systems were constructed to provide scanning laser beams with different beam directions by replacing the detachable beam-deflection modules as follows: (1) Simple mirror type directing the beam opposite to the incident beam, with a system height of 4 mm; (2) Beam splitter type directing the beam perpendicular to the incident beam, with a system height of 6 mm; and (3) Prism mirror type directing the beam forward relative to the incident beam, with a system height of 8 mm. The systems had distinctive features rendering each suitable for different applications. Thus, these laser scanning systems offer compact solutions for laser scanning image projection.

The excellent electrical and optical properties of graphene provide the possibility for its application in transparent electromagnetic shielding films. The multi-layer graphene films were designed and prepared, and the average transmittances of 1–4 layers graphene in the 3–5 μm band were 97.19%, 94.89%, 93.29%, and 91.16%, respectively. The average shielding effectiveness (SE) in the 12 GHz–18 GHz frequency band is 1.52 dB, 3.07 dB, 4.58 dB, and 5.83 dB, respectively. The direct stacking of graphene can effectively improve shielding efficiency and maintain high optical transmittance in the wide infrared spectral range. This demonstrates the high infrared transmittance of multi-layer graphene film and is a method to improve electromagnetic shielding effectiveness.

Understanding the drying kinetics of paints and coatings is crucial in various industrial applications due to their significant impact on reflective properties. This study investigates the dynamic changes in the refractive index of adhesives and varnishes during their transition from liquid to solid states upon drying, while the imaginary part of the refractive index was measured only in the fully dried samples. Our results reveal that the refractive indices of liquid varnishes and lacquers change during the drying process, increasing from 1.382 to 1.5119. Similarly, the refractive indices of adhesives change from 1.440 to 1.452 during drying. The use of refractive index data enhances the optimization of drying process and offers deep insights into the materials’ optical characteristics, crucial for understanding material behavior during drying and its influence on the end-product’s performance.

Two bifunctional nanophosphors of BaLaAl₃O₇:xTb³⁺ (BLAO:Tb) and BaYAl₃O₇: yTb³⁺ (BYAO:Tb) have been designed and prepared by the high-temperature solid state reaction method. The green photoluminescence (PL) of the BYAO:Tb sample is significantly stronger than that of the BLAO:Tb sample. The optimal Tb³⁺ doping concentrations of two systems are 4 and 5 mol%, respectively. In addition, the BLAO:Tb and BYAO:Tb powders exhibit different lifetimes, i.e., single and double exponential decay processes in turn. Furthermore, the green mechanoluminescence (ML) phenomena of two kinds of nanophosphors are also observed when they are scratched with a pen. The ML intensity of the BYAO:4 Tb sample is weaker than that of the BLAO:5 Tb sample under almost the same external force, but the former becomes more intense as the scratching force increases. The PL/ML mechanism is analyzed based on the measurements of thermoluminescence (TL) spectra, and it is found that the initial total concentration of the trapped carriers in the BYAO:4 Tb samples is n₀ = 2.959 × 10⁴ cm⁻³, which is lower than that of the BLAO:5Tb³⁺ sample (3.301 × 10⁴ cm⁻³). However, the activation energies of the former are generally smaller than those of the latter. In conclusion, the new PL/ML bifunctional material has a better application potential because the novel aluminate ABAl₃O₇ structure is best suited for doping trivalent terbium ions.