Optical Review最新文献

We numerically and experimentally developed a cantilever that provided both fast and analog actuation for THz metamaterials (MMs) by properly geometrizing a dimpled tip. Owing to its small size and light mass, the cantilever had a high mechanical resonance at 705 kHz. Cantilever arrays were fabricated with different tip gaps and integrated into a ladder-shaped MM (LS-MM). By changing the tip gap from 0.80 to 0.32 μm, the resonance of the transmittance spectrum changed from 1.235 to 0.795 THz, indicating that the reconfigurable LS-MM was capable of continuously tuning the resonance of the THz wave transmission with the tip gap. Additionally, the dimple served as an anti-stiction structure, providing the cantilever with a fabrication yield of 99.8%. This work shows a practical pathway to high-performance active metamaterials, which holds potential in advanced THz technologies such as 6G communications and fast imaging.

Imaging is a longstanding research topic in optics and photonics and is an important tool for a wide range of scientific and engineering fields. Computational imaging is a powerful framework for designing innovative imaging systems by incorporating signal processing into optics. Conventional approaches involve individually designed optical and signal processing systems, which unnecessarily increased costs. Computational imaging, on the other hand, enhances the imaging performance of optical systems, visualizes invisible targets, and minimizes optical hardware. Digital holography and computer-generated holography are the roots of this field. Recent advances in information science, such as deep learning, and increasing computational power have rapidly driven computational imaging and have resulted in the reinvention these imaging technologies. In this paper, I survey recent research topics in computational imaging, where optical randomness is key. Imaging through scattering media, non-interferometric quantitative phase imaging, and real-time computer-generated holography are representative examples. These recent optical sensing and control technologies will serve as the foundations of next-generation imaging systems in various fields, such as biomedicine, security, and astronomy.

Increasing the sensitivity of image sensors is a major challenge for current imaging technology. Researchers are tackling it because highly sensitive sensors enable objects to be recognized even in dark environments, which is critical for today’s smartphones, wearable devices, and automobiles. Unfortunately, conventional image-sensor architectures use light-absorptive color filters on every pixel, which fundamentally limits the detected light power per pixel. Recent advances in optical metasurfaces have led to the creation of pixelated light-transmissive color splitters with the potential to enhance sensor sensitivity. These metasurfaces can be used instead of color filters to distinguish primary colors, and unlike color filters, they can direct almost all of the incident light to the photodetectors, thereby maximizing the detectable light power. This review focuses on such metasurface-based color splitters enabling high-sensitivity color-image sensors. Their underlying principles are introduced with a focus on dispersion engineering. Then, their capabilities as optical elements are assessed on the basis of our recent findings. Finally, it is discussed how they can be used to create high-sensitivity color-image sensors.

UV curing hybrid materials via the photo polymerization have significant significance for the lithography fields due to the high resolution. In this work, the UV-curable SiO₂ materials with chelating compound structure are synthesized by photosensitive Sol–Gel approach, which have a wide absorption band at 267 nm. With the UV light irradiation, the chelating compound structure decomposes and the solubility of the film in organic solvent decreases. Based on this premise, the presented material exhibits the ability to fabricating highly ordered SiO₂ microarrays on several substrates through UV photolithography. The SiO₂ micro arrays can be used to as templates to prepare noble metal micro-structures, which own wide potential application prospects in highly ordered SERS substrates with high activity and reproductivity for trace detection.

This paper focuses on the channel impairments separability of two histogram-based features, asynchronous amplitude histograms (AAH) and asynchronous delay-tap plot (ADTP), commonly used in direct-detection optical performance monitoring (OPM) techniques. This paper presents an in-depth study of the conditions under which these two histogram features are applicable in OPM. These high-dimensional features, AAH and ADTP, are dimensionally reduced using a state-of-the-art data visualization algorithm called Uniform Manifold Approximation and Projection (UMAP) algorithm. After data visualization, it can be found these two histogram-based features have some limitations in distinguishing between different levels of impairments in some specific cases. These features cannot achieve high accuracy in monitoring optical performance in these given situations, no matter how complex the classifier is designed. Extensive simulation experiments were performed to study the classification performance of the two histogram features in the single and multiple impairments cases. The results show that both AAH and ADTP can be used to monitor cumulative dispersion (CD) and optical signal to noise ratio (OSNR) in the case of the single impairment. In addition, the monitoring performance of both features is better for dispersion in the case of multiple impairments coexistence, while both have limitations for OSNR monitoring. However, the anti-dispersion interference ability of ADTP is better than that of AAH. The plausibility of the study results is verified by estimating the channel impairments under different conditions using a deep neural network-based (DNN) identifier. The impairments separation visualization results of UMAP are highly consistent with the estimation results of the DNN-based classifier, achieving the interconnection of usefulness and practicality.

In this paper, we employ the quantum trajectory Monte Carlo model to simulate the momentum distribution of Argon atoms during tunneling ionization. Our analysis illustrates the use of semi-classical models to study the changes in electron trajectories under different laser field intensities. And by studying the different subcycles, the changes of the interference pattern are observed. Our approach successfully observes the interference patterns resembling fishbone and spider stripes. We delve into the subperiodic interference structures present in the photoelectron momentum distributions. Specifically, we investigate the correlation effects of ionization trajectories on the interference fringes within the same period and in adjacent periods. Our analysis demonstrates that the holographic interference fringe results from the superposition of direct ionization trajectories and scattering trajectories. We elucidate the mechanisms underlying the formation of above-threshold ionization (ATI) ring structures and temporal double-slit interference patterns. Additionally, we investigate how wave packets perceive the Coulomb potential and its impact on interference phenomena under varying field intensities. Notably, without the Coulomb potential, the original spider-like holographic interference pattern disappears, replaced by temporal double-slit interference fringes similar to those observed within a comparable time frame.

A filter-free microwave photonic single-sideband mixer based on dual-polarization dual-drive Mach–Zehnder modulator (DPol-DDMZM) is proposed and verified experimentally. By adjusting the bias voltages of two DDMZMs, each DDMZM generates a single-sideband (SSB) signal with upper or lower sideband. The optical carrier is cancelled by adjusting the polarization controller before a polarizer. The single-sideband frequency upconversion and downconversion are independently achieved with the mixing spurs suppressed. The proposed frequency converter has a large operating bandwidth since no filter is used, and there is no dispersion-induced power fading due to the SSB modulation when transmitting in a long fiber with a dispersion. Experimental results show that all the mixing spurs are well suppressed over a wideband frequency range, and the maximum sideband suppression ratio of desired signal is up to 36 dB.