Hasil untuk "Applied optics. Photonics"

Christopher M Lalau-Keraly, Samarth Bhargava, Owen D. Miller et al.

We present an adjoint-based optimization for electromagnetic design. It embeds commercial Maxwell solvers within a steepest-descent inverse-design optimization algorithm. The adjoint approach calculates shape derivatives at all points in space, but requires only two "forward" simulations. Geometrical shape parameterization is by the level set method. Our adjoint design optimization is applied to a Silicon photonics Y-junction splitter that had previously been investigated by stochastic methods. Owing to the speed of calculating shape derivatives within the adjoint method, convergence is much faster, within a larger design space. This is an extremely efficient method for the design of complex electromagnetic components.

Qiang Yang, Yichang Shou, Yongqi Zhao et al.

Quantitative phase microscopy (QPM) has been an effective technique to examine stain-free biomedical tissues and cells. The development of simple and compact QPM technology with planar optical components enhances system integration and portability. Here, we propose a QPM technique by inserting a metasurface-assisted optical differential system to replace the bulky optical elements in the conventional microscope. The differential scheme allows for the separation of amplitude and phase information for a complex field, offering an opportunity to quantitatively analyze the phase distribution of samples. The experimental demonstrations showcase the well-executed application of the proposed method to artificial phase samples, paramecium cells, fishtail cross-cut tissue, and diatom cells. Notably, our imaging system allows switching between four imaging modes—brightfield, optical spatial differential, differential interference contrast, and QPM. At a high level, this work may drive the advancement of single-shot and multi-mode integrated phase microscopy for biomedical imaging and diagnostics.

Shiqi Feng, Xuquan Wang, Xiong Dun et al.

Encoded computational hyperspectral cameras, propelled by advances in compressed sensing theory, making both miniaturization and real-time hyperspectral imaging feasible. Spectral-encoded or spatial-encoded hyperspectral imaging strategy have limited numbers of design parameters in optical components, leading to severe ill-posedness in hyperspectral images reconstruction, which constrain overall imaging quality. However, spatial-spectral-encoded hyperspectral imaging strategy which simultaneously performs spatial and spectral encoding entailing more powerful modulation, alleviating ill-posed problems and improving the quality of hyperspectral images. In this paper, we present a co-modulation framework based on diffractive optical element (DOE) and Superposition Fabry&#x2013;Perot (SFP) filter array for computational hyperspectral camera that integrates these two components with a transformer-based reconstruction network through end-to-end learning. The learned DOE and SFP filter encode the hyperspectral datacube on the sensor via phase and amplitude modulation, and the transformer-based network accurately reconstructs the images from sensor measurements. We conduct extensive simulations to analyze and validate the relatively contributions of the DOE, SFP filter, and transformer-based reconstruction algorithm to the significantly improved performance of hyperspectral image reconstruction across various ablation study models. We further investigate and identify the <inline-formula><tex-math notation="LaTeX">$\mathbf {4\times 4}$</tex-math></inline-formula> SFP filter unit configuration as the most effective design for achieving a balance between spectral fidelity and spatial resolution. Our results show that the proposed system outperforms state-of-the-art methods in hyperspectral images reconstruction quality, excelling in both spatial and spectral detail recovery, and maintaining good performance against realistic noise levels.

Wei Yuan, Shaoqiang Zheng, Zheng Zhang et al.

In this work, we confirm a Pr3+:LiYF4 pulsed laser with high power and high energy at 639 nm based on the acousto-optic cavity dumping technique. The maximum average output power, narrowest pulse width, highest pulse energy and peak power of the pulsed laser at a repetition rate of 0.1 kHz are 532 mW, 112 ns, 5.32 mJ and 47.5 kW, respectively. A 639 nm pulsed laser with such high pulse energy and peak power has not been reported previously. Furthermore, we obtain a widely tunable range of repetition rates from 0.1 to 5000 kHz. The diffracted beam quality factors M2 are 2.18 (in the x direction) and 2.04 (in the y direction). To the best of our knowledge, this is the first time that a cavity-dumped all-solid-state pulsed laser in the visible band has been reported. This work provides a promising method for obtaining high-performance pulsed lasers.

C. G. Candido, C. G. Candido, J. A. Principe

Oil spills represent a significant environmental hazard necessitating timely detection to mitigate their detrimental effects. Synthetic Aperture Radar (SAR) technology serves as a remote sensing (RS)-based tool capable of detecting oil spills under varying weather conditions and at all times of day. SAR polarimetry, which assesses the polarization of the backscattered SAR signal, can effectively discriminate oil spills from other features that may manifest as dark regions in the SAR images. The integration of machine learning algorithms offers significant potential for enhancing the accuracy and efficiency of oil spill detection through SAR polarimetry. In recent years, several studies have introduced machine learning-based methodologies for this purpose, yet a comprehensive evaluation of their real-world performance remains essential. This study aimed to assess the efficacy of a machine learning (ML)-based approach for oil spill detection utilizing features derived from a dual-polarimetric decomposition method applied to Sentinel-1 SAR data. Results show that the machine learning-based approach achieved notable accuracy in oil spill detection reaching a score of 0.569 for intersection over union and 72.50 for f1-score of oil spill areas. Overall, this research underscores the potential of ML techniques as valuable tools for oil spill detection via SAR polarimetry.

A. A. Pedro, F. Dadrass Javan, S. Georgievska et al.

The expansion of invasive species is a global challenge that leads to the loss of biodiversity habitat, and there are few tools to control it. In S&atilde;o Paulo, identification of invasive species is done through field inspections, in parts of Conservation Units and parks, making it difficult to map all tree individuals for adequate management and coping strategies. This manuscript presents a workflow that combines Unmanned Aerial Vehicles (UAVs), or drones, with Artificial Intelligence (AI) to accurately map invasive species in the Atlantic Forest. It describes best practices on how to conduct drone flights to map the forests, exponentially expanding the range of identification and efficiency in invasive tree species management. It also presents an AI workflow that uses few-shot learning and Explainable AI techniques (to guarantee transparency and understanding of the decisions made by the algorithms). Preliminary results indicate that the method obtains acceptable results in the range of 70 percent accuracy for <em>Archontophoenix cunninghamiana</em> (popular name: Seaf&oacute;rtia), an invasive Australian palm.

Yong Zhou, Kun Wang, Junkun Mao et al.

Achieving a high sensitivity for practical applications has always been one of the main developmental directions for wearable flexible pressure sensors. This paper introduces a laser speckle grayscale lithography system and a novel method for fabricating random conical array microstructures using grainy laser speckle patterns. Its feasibility is attributed to the autocorrelation function of the laser speckle intensity, which adheres to a first-order Bessel function of the first kind. Through objective speckle size and exposure dose manipulations, we developed a microstructured photoresist with various micromorphologies. These microstructures were used to form polydimethylsiloxane microstructured electrodes that were used in flexible capacitive pressure sensors. These sensors exhibited an ultra-high sensitivity: 19.76 kPa−1 for the low-pressure range of 0–100 Pa. Their minimum detection threshold was 1.9 Pa, and they maintained stability and resilience over 10,000 test cycles. These sensors proved to be adept at capturing physiological signals and providing tactile feedback, thereby emphasizing their practical value.

N. Aslan, D. Koc-San

The aims of this study are to detect the land-cover maps and land surface temperatures using Landsat time series and analyse the relation between the land-cover and land surface temperatures (LST) and their changes in time. For these purposes initially, land-cover maps were generated rapidly using land cover indices and automatic thresholding. The land-cover indices used in this study are Normalized Difference Vegetation Index (NDVI), Modified Normalized Difference Water Index (MNDWI), Index-Based Built-Up Index (IBI), Modified Bare-Soil Index (MBI), Plastic-Mulched Landcover Index (PMLI), Plastic Greenhouse Index (PGI) and Normalized Burn Ratio Thermal (NBRT) Index. Then, using the thermal bands of Landsat satellites, LST maps were created. Finally, the land-cover and LST changes were examined. The Kumluca district of Antalya, which includes extensive greenhouse areas as well as urban, vegetation, bareland, water, was selected as study area. Between the years 2004 and 2021, within the study area the greenhouse areas increased significantly, the urban area expanded and some areas exposed to fire, especially the fire in 2016. Therefore, the images within this time period were used. The overall accuracies for land-cover maps were computed as 76%, 79%, 79%, 89% and 86% for the years 2004, 2009, 2013, 2017 and 2021, respectively. The results obtained from the study reveal that while greenhouse and urban areas were increased, the vegetation areas were decreased significantly within this time period. In addition, generally increases were observed for LST values of all land-cover classes and the highest LST values were detected for the burned, bareland, urban and greenhouse areas.

A. A. Morozov, O. S. Sushkova, M. V. Sinkin et al.

This work aims to study and develop methods and tools for analyzing video-EEG monitoring of delayed cerebral ischemia after subarachnoid haemorrhage. A study was made of methods and algorithms for processing video images, which are supposed to be used to recognize life events and medical care for a patient, which can lead to artefacts in the patient’s EEG records. An approach to video monitoring of the patient was proposed and tested on real video monitoring data using object-oriented logic programming methods in combination with neural network methods for image analysis.

Jin Woo Oh, Seokyeong Lee, Hyowon Han et al.

Abstract Optical encryption technologies based on room-temperature light-emitting materials are of considerable interest. Herein, we present three-dimensional (3D) printable dual-light-emitting materials for high-performance optical pattern encryption. These are based on fluorescent perovskite nanocrystals (NCs) embedded in metal-organic frameworks (MOFs) designed for phosphorescent host-guest interactions. Notably, perovskite-containing MOFs emit a highly efficient blue phosphorescence, and perovskite NCs embedded in the MOFs emit characteristic green or red fluorescence under ultraviolet (UV) irradiation. Such dual-light-emitting MOFs with independent fluorescence and phosphorescence emissions are employed in pochoir pattern encryption, wherein actual information with transient phosphorescence is efficiently concealed behind fake information with fluorescence under UV exposure. Moreover, a 3D cubic skeleton is developed with the dual-light-emitting MOF powder dispersed in 3D-printable polymer filaments for 3D dual-pattern encryption. This article outlines a universal principle for developing MOF-based room-temperature multi-light-emitting materials and a strategy for multidimensional information encryption with enhanced capacity and security.

Yousuf Khan, Muhammad A. Butt, Svetlana N. Khonina et al.

In this work, a dielectric photonic crystal-based thermal sensor is numerically investigated for the near-infrared spectral range. An easy-to-fabricate design is chosen with a waveguide layer deposited on a silicon dioxide substrate with air holes drilled across it. To sense the ambient temperature, a functional layer of polydimethylsiloxane biguanide polymer is deposited on the top, the optical properties of which vary with changes in the temperature. An open-source finite-difference time-domain-based software, MEEP, is used for design and numerical simulation. The design of the sensor, spectral properties, and proposed fabrication method are part of the discussion. The performance of the sensor is investigated for an ambient temperature range of 10 to 90 °C, for which the device offers a sensitivity value in the range of 0.109 nm/°C and a figure-of-merit of 0.045 °C⁻¹. Keeping in mind the high-temperature tolerance, inert chemical properties, low material cost, and easy integration with optical fiber, the device can be proposed for a wide range of thermal sensing applications.

Lin Xu, Huanyang Chen

S. Kobtsev

B. Sephton, Adam Vall´es, I. Nape et al.

Renhong Gao, Haisu Zhang, Fang Bo et al.

Xinyao Huang, Cuicui Lu, Chao Liang et al.

Abstract Nonreciprocity is important in both optical information processing and topological photonics studies. Conventional principles for realizing nonreciprocity rely on magnetic fields, spatiotemporal modulation, or nonlinearity. Here we propose a generic principle for generating nonreciprocity by taking advantage of energy loss, which is usually regarded as harmful. The loss in a resonance mode induces a phase lag, which is independent of the energy transmission direction. When multichannel lossy resonance modes are combined, the resulting interference gives rise to nonreciprocity, with different coupling strengths for the forward and backward directions, and unidirectional energy transmission. This study opens a new avenue for the design of nonreciprocal devices without stringent requirements.

Ryszard S. Romaniuk, A. Smolarz, Waldemar Wójcik

Wilga 2021 Summer Symposium on Photonics Applications and Web Engineering was the 48th edition of the research and technical meetings series [1,2]. Traditionally, the whole week lasting annual series of technical conferences and topical sessions was scheduled to be held on 26 May – 02 June 2020 in Wilga resort near Warsaw, owned by the Warsaw University of Technology. Nearly 150 participants took part in all of the Wilga 2021 events, most of them being young researchers active in all aspects of photonics, electronics and ICT science and technology. Wilga Symposium also embraces hardware and software technologies associated with photonics like optics, optical engineering, optoelectronics, electronics and electrical engineering, mechatronics, chemical and material engineering, applied physics, industrial solutions and applications. Around 100 papers were presented during Wilga 2021, oral and poster. Out of this number, some papers chosen by authors are published in this volume of Proc. SPIE mostly related to photonics. The major change was that during Wilga 2020 and 2021 Symposia, during summer editions, no traditional large young researcher sessions at large were possible to be organized.

Zhaokun Wang, Daodang Wang, T. Zhu et al.

Graded index multimode fibre (GIMF) has emerged as a promising platform for two- and three-dimensional nonlinear optics. Based on the nonlinear multimodal interference technique, GIMF has demonstrated the saturable absorption effect and applied for fibre-based-laser short pulse generation as versatile, wideband ultrafast optical switches. Herein, this review presents the basic principles and the optical properties of the GIMF-based saturable absorber (SA). With this proposed GIMF-based SA device, mode-locking fibre lasers in the wavelength range of 1, 1.55, and 2 μm are realized. Particular focus is on the tunable and multi-wavelength mode-locked fibre lasers, various kinds of soliton generation and large energy soliton generation and a detailed summary of the current advances are given.

A. Forbes, R. Chérif, A. Dudley et al.

Africa has a long history in optics, but decades of turmoil have seen optical science in Africa advance only slowly, punching far below its weight. But a younger generation of scientists hold promise for the brighter future, addressing continental issues with photonics. In this Feature Issue on Optics in Africa we capture some of the exciting optical research from across the continent in 51 research reports, covering both fundamental and applied topics. The issue is supplemented by invited review articles that offer authoritative perspectives on the historical development of key research fields, from early advances in lasers to present-day progress in photonic materials. To encourage the exploration of new research directions, the issue has several tutorial articles that lower the entry barrier for emerging researchers, while highlighting the scope of research on the continent and its international context.

C. M. Chang, J. J. Jaw

When a target lies on discontinuous surfaces, the footprint of a laser rangefinder covering multiple ranges causes mixed pixels effect and significantly distorts the ranging quality. Meanwhile, the ranging error of incidence angle effect is triggered by a deformed footprint containing various ranges as well. Based on the commonality of causing ranging errors within one footprint, this study proposed an approach to tackle “generalized mixed pixels effect” correcting ranging errors involving in deformed footprint cases. Errors caused by generalized mixed pixels effect vary in rangefinders and are difficult to be uniformly treated. A correction model was formulated through integrating individual effects by considering the physical and geometrical aspects of laser ranging. An adjustment procedure was followed to estimate the parameters of the correction equation taking all observation uncertainties into account. To analyze the individual effects and eventually combine them into a complete model, a five-case workflow has been developed. Firstly, a divergence angle estimation method was presented to eliminate the mixed pixels effect by a decentering approach. Incidence angle effect was modeled and parameter was estimated by adjustment techniques. Particularly, since incidence angles are usually unknown in field surveys, an iterative estimation procedure was designed to obtain the optimal incidence angle of target points. Finally, offset correction accounting for generalized mixed pixels effect was formulated. Through the experimental tests on Trimble M3 DR 2” and Topcon GPT-3002LN, it is confirmed that the proposed method effectively resolves the ranging errors and preserves the ranging quality under generalized mixed pixels effect.