Optical Review最新文献

Owing to the rapid growth of digital information, demand for archival storage with high data transfer rate, large capacity, longevity, low power consumption, and low running cost has surged. Although holographic data storage (HDS) is considered as a promising candidate for next-generation archival storage due to its potential in these areas, it has not been released commercially due to difficulties in stable recording and reproduction across the whole recording area or multibook area. In this study, we proposed a robust multibook recording technique based on signal beam phase optimization using the Gerchberg–Saxton (GS) algorithm. We optimized the target distribution of the signal beam amplitude at the Fourier plane for the GS algorithm, considering the hologram recording and reproduction characteristics, such as DC suppression, inter-book-interference (IBI) reduction, and the signal-to-noise ratio (SNR). Optical simulation of multibook recording and reproduction shows that IBI can be properly reduced, and sufficient SNR can be retained even if 13.6% book misalignments occur during recording. In addition, combining the proposed technique with an accurate book alignment method could increase the HDS capacity by 33.9%.

When a hydrophone with a vibrating membrane is placed in water, the ultrasonic waves to be detected diffract and reflect. Therefore, conventional hydrophones cannot accurately measure the sound field distribution. Another noncontact method for measuring the sound field distribution is the Schlieren method. However, this method requires meticulous optical axis adjustment using a Schlieren lens and a knife edge, and this method is not versatile. Therefore, a laser hydrophone, which uses the self-coupling effect of a semiconductor laser to detect ultrasonic waves without contact with the sound field, is developed, and the sound field is investigated. The optical system of the laser hydrophone is composed of only a few components. In addition, because ultrasonic waves can be detected using only a small amount of light, no optical axis adjustment is necessary. The frequency response of the laser hydrophone is flat. The upper limit of the detectable frequency is determined by the relationship between the large diameter of the laser beam and the frequency of the ultrasonic waves. The measured sound pressure distribution of the laser hydrophone qualitatively agreed with that of the simulation.

Given that silicon-on-insulator (SOI) has a high refractive index contrast and intrinsic birefringence, photonics devices based on SOI are typically polarization-sensitive. To address this issue, a novel broadband mid-infrared polarization rotator (PR) based on cascaded stepped waveguides was put forward. It can achieve polarization conversion between the fundamental TM₀ and TE₀ modes through mode hybridization formed in asymmetric waveguides. The finite-difference time-domain (FDTD) method was employed to explore its polarization rotation characteristics and optimize the device structure. Simulation results demonstrate that at the central wavelength of 2.53 µm, the maximum polarization extinction ratio (PER) can attain 40.02 dB, the polarization conversion efficiency (PCE) exceeds 99.8%, and the insertion loss (IL) is as low as 0.12 dB. Moreover, the operating bandwidth is expanded to 490 nm (spanning from 2.28 to 2.77 µm). Meanwhile, the device length is merely 16.4 μm. Furthermore, tolerance analysis indicates that the device has good manufacturing tolerance. Owing to its high PER, large bandwidth, and small footprint, the proposed PR has significant application potential in mid-infrared photonic integrated circuits (PICs).

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.