Hasil untuk "Applied optics. Photonics"

Daniele Pirone, Giusy Giugliano, Michela Schiavo et al.

Virtual staining is the current state-of-the-art computational technique to cleverly enhance intracellular specificity in unstained biological samples by using convolutional neural networks (CNNs) trained on co-registered pairs of unstained/stained images. While effective, this approach suffers from unpredictable biases inherent to fluorescence microscopy and encounters challenges when applied to flow cytometry data as it would require accurate co-registration on a huge number of images. Here, we present a novel method that exploits for the first time a Holotomography-driven learning to completely eliminate the need for co-registration. We demonstrate that training a CNN on a stain-free dataset of 3D refractive index tomograms of flowing cells unlocks stain-free intracellular specificity for the first time in quantitative phase imaging flow cytometry. This self-supervised solution, by circumventing the critical obstacle of fluorescence co-registration, opens unprecedented perspectives for label-free, high-throughput imaging flow cytometry, offering a powerful new paradigm for advanced 2D and 3D single-cell analysis.

Tatsuki Tahara

I propose a digital holographic microscopy technique in which complex amplitude distributions at multiple wavelengths are simultaneously obtained with a common-path self-reference interferometer and a monochrome image sensor. The computational coherent superposition scheme is applied to reconstruct a multiwavelength holographic image from a small number of wavelength-multiplexed phase-shifted holograms. Optical systems adopting a commercially available optical microscope with a light-emitting diode and a halogen lamp are constructed and their applicabilities to multiwavelength three-dimensional microscopy and quantitative phase microscopy are experimentally demonstrated. The possibility of single-shot measurement with a monochrome image sensor is discussed.

Rong Ma, Wen Zhang, Xiaowei Wu et al.

As an essential quantum resource, the intensity-difference squeezed state based on four-wave mixing (FWM) in atomic vapor is widely applied in quantum information processing. In particular, a high intensity-difference squeezing bandwidth is vital for the realization of high-speed information processing. However, limited by the bandwidth of photodetectors, broadband intensity-difference squeezed state based on this system has not yet been reported. Here, we developed a transimpedance broadband balanced homodyne detector at 895 nm, achieving a bandwidth greater than 100 MHz and a maximum signal-to-noise ratio of 15 dB with 4 mW optical power. Utilizing this detector in a nondegenerate FWM process based on cesium vapor, we experimentally achieved broadband intensity-difference squeezing with a bandwidth of 100 MHz, which yielded a maximum squeezing of −7.17 ± 0.8 dB between 20 and 40 MHz. Meanwhile, using this detector, we experimentally investigated the cavity-enhanced FWM process, achieving a squeezing level of −6.07 ± 0.5 dB within a 4 MHz frequency range, which is limited by the cavity bandwidth. This work provides a reliable detection tool and experimental foundation for the research and application of broadband squeezed light sources based on FWM.

Hani J. Kbashi, Sergey V. Sergyev

Optical rogue waves are a nonlinear phenomenon that offers a unique opportunity to gain fundamental insights into wave interaction and behavior, and the evolution of complex systems. Optical systems serve as a suitable testbed for the well-controlled investigation of this natural phenomenon, which cannot be easily studied in an ocean environment. Additionally, such systems offer practical applications in telecommunications and optical signal processing, making this topic a vital area of research. Fiber lasers are considered the best candidates for demonstrating and investigating the emergence of optical rogue waves. In particular, they offer significant advantages in nonlinear dynamics due to faster field evolution and a higher number of events that can be recorded within a relatively short time. In this paper, we present the development mechanisms of optical rogue wave events. It was found that multimode vector instability, pulse–pulse interaction, and soliton rain are the main nonlinear dynamics leading to the formation of optical rogue wave events.

Yuxin Tian, Boyu Dong, Yaxuan Li et al.

This paper presents a wide-bandwidth back-illuminated modified uni-traveling-carrier photodiode (MUTC-PD) packaged with standard WR-5 rectangular waveguide for high-speed wireless communications. With optimized epitaxy structure and coplanar waveguide electrodes, the fabricated 4-μm-diameter PD exhibits ultra-flat frequency response and high saturation power. Integrated passive circuits including low-loss bias-tee and E-plane probe are designed to package the PD into a compact module with waveguide output. The packaged PD module has demonstrated a flat frequency response with fluctuations within ±2.75 dB over a broadband of 140–220 GHz and a high saturated output power of −7.8 dBm (166 μW) at 140 GHz. For wireless communication applications, the packaged PD is used to implement 1-m free space transmission at carrier frequencies of 150.5 and 210.5 GHz, with transmission rates of 75 and 90 Gbps, respectively.

Andrey Pryamikov

Abstract The backpropagation algorithm, the most widely used algorithm for training artificial neural networks, can be effectively applied to the development of digital signal processing schemes in the optical fiber transmission systems. Digital signal processing as a deep learning framework can lead to a new highly efficient paradigm for cost-effective digital signal processing designes with low complexity.

Yang Cao, Zupeng Zhang, Xiaofeng Peng et al.

An improved non-convex optimized phase recovery algorithm is used to compensate for wavefront aberrations caused by atmospheric turbulence and pointing errors in the vortex beam. The algorithm is divided into two parts: initialization and iteration. To reduce the effect of outliers, truncation rules are formulated in the initialization phase using the robustness of the sample median to obtain an initial value that is close to the global optimum. The relationship between the results of adjacent iterations is used in the iterations to calculate new weight coefficients, which are applied to the gradient descent to ensure the accuracy of the recovery results. Simulation experiments are carried out for different channel environments and different modes, and the results show that the improved phase recovery algorithm can accurately compensate for distorted wave fronts. The improved algorithm recovers the best results at different turbulence intensities and under the influence of different pointing errors. The recovered Strehl ratio can reach 0.9 and the mode purity can reach 0.92. Single-mode and multi-mode simulations were carried out, and the results show that the improved algorithm is effective and robust.

Yesheng Chen, Chen Yang, Shan Liu et al.

Quasi‐phase matching (QPM) is a technique in nonlinear optics for achieving efficient energy exchange among optical waves at different frequencies, by spatially modulating the quadratic nonlinearity (χ (2)) of the medium. To realize the full potential of QPM, 3D spatial modulation of χ (2) is required. This has become experimentally feasible recently thanks to the invention of femtosecond laser‐based nonlinearity engineering in ferroelectric crystals. Herein, the first experimental demonstration of QPM second harmonic generation (SHG) in a nonlinear cubic crystal system is presented, in which χ (2) modulations form simple cubic, body‐centered cubic, face‐centered cubic, and diamond cubic lattices, respectively. The experimental results indicate that these nonlinear cubic structures share the same primary reciprocal lattice vectors (RLVs), but possess different Fourier coefficients (in conventional cells), leading to SHG with similar angular resonances but various intensity distributions in the far field. This work contributes to a comprehensive understanding of nonlinear optical processes in 3D periodic media, and thus sheds light on the development of high‐performance QPM devices.

Dan Yan, Zi-Hui Meng, Li-Li Qiu et al.

Nanostructured transition metal oxides (TMOs) semiconductor materials, whose photoelectric properties are significantly improved due to their nanostructures, have attracted more and more attention in recent years. As a functional material with periodic nanostructures and unique optical properties, photonic crystals (PhCs) have become an important option for nanostructuring semiconductor materials. The TMO semiconductor PhC (TMOPC), which is integrated by combining TMO with PhC, not only has the sensitivity of the TMO semiconductor to environmental stimulus, but also can improve the utilization rate of light and make the material have the optical response due to the optical modulation of PhC, such as slow light effect. The application of TMOPCs is widely promoted and expanded due to the improvement of its performance. Herein, this review summarizes the preparation methods of 3D TMOPCs in recent years and their main applications. The limitation and potential development of 3D TMOPCs in preparation and application are also discussed and prospected.

A. Alattas, A. Alattas, P. van Oosterom et al.

During an incident, many people that are located in indoor environments require to follow emergency evacuation procedures. The ‘emergency evacuation’ term has been defined as ‘a critical movement of people from a dangerous area due to the risk or an incident of a tragic event’ (Bonabeau, 2002). An emergency evacuation could be needed in a life or death situation, regardless if it begins with a natural non-intended incident or a terrorist attack. Many researchers have studied the behaviour of the people during the evacuation because of several incidents with panic attacks that have led to injuries including death of people being crushed or trampled down by others. In crisis situation, the perception of the indoor environment, which differs from person to person, play a critical role in the evacuation. Also, the access rights of the indoor spaces are different from those rights (and restrictions) during normal times. They may positively impact the movements of the people during the evacuation by providing suggestions for shorter/better route. This paper addresses the impact of the access rights of the indoor spaces during an emergency evacuation. We employ the conceptual model of LADM-IndoorGML that defines the accessibility of the indoor spaces based on the rights, restrictions, and responsibilities of the user of the indoor space. The access rights of the indoor spaces are affected by the crisis event and this needs to be modelled explicitly (and before crisis situation). Actually, the rights/restrictions persons have on spaces is time dependent: normal operation hours, outside normal operation hours (e.g. during night time in case of a University building) or during crisis times. These actual/valid rights and restrictions affect the movement/accessibility of the users to reach the nearest emergency exits or the safe zone. For this reason, different scenarios have to be developed to study the impact of the accessibilities for different types of users. In this paper we will present the 3D model of an educational building that was built for the purpose of evacuation study. The 3D model is supported by real data for all spaces from the facility management department such as information on departments, sections, groups of users (visitors, employees, and students), and public/private spaces, etc. and a real evacuation exercise. We consider it extremely important to develop our information model based on international standards (LADM/ISO 19152, OGC IndoorGML, ISO 19141, ISO 19107) as we expect that this information will be part of the future ‘building infrastructure’ and applications all over the world can understand and use this data when entering or leaving a certain building both during normal and crisis situations. Different types of applications are anticipated to be based on this information model; e.g. mobile indoor routing app (for normal building users and Emergency Response Team members), crisis evacuation desktop application for command centre, etc.

M. K. Patasaraiya, B. Sinha, J. Bisaria et al.

Climate change poses a severe threat to the forest ecosystems by impacting its productivity, species composition and forest biodiversity at global and regional level. The scientific community all over the world is using remote sensing techniques to monitor and assess the impact of climate change on forest ecosystems. The consistent time series data provided by MODIS is immensely used for developing a different type of Vegetation indices like NDVI (Normalized difference vegetation indices) products at different spatial and temporal resolution. These vegetation indices have significant potential to detect forest growth and health, vegetation seasonality and different phenological events like budding and flowering. The current study aims to understand the impact of climate change on Teak and Sal forest of STR (Satpura tiger reserve) in central India by using Landsat and MODIS time series data. The rationale for taking STR as study site was to attribute the changes exclusively to climate change as there is no anthropogenic disturbance in STR. A change detection analysis was carried out to detect changes between the period 2017 and 1990 using Landsat data of October month. To understand the inter-annual and seasonal variation of Teak and Sal forests, freely available MOD13Q1 product (250 m, 16 days’ interval) was used to extract NDVI values for each month and four seasons (DJF, JJAS, ON, MAM) for the period 2000 to 2015. The climatic data (rainfall and temperature) was sourced from IMD (India Meteorological Department) at different resolutions (1, 0.5 and 0.25 degree) for the given period of the study. A correlation analysis was done to establish a causal relationship between climate variable (temperature and rainfall) and vegetation health (NDVI) on a different temporal scale of annual, seasonal and month. The study found an increasing trend in annual mean temperature and no consistent trend in total annual rainfall over the period 2000 to 2015. The maximum percentage change was observed in minimum temperature over the period 2000 to 2015. The average annual NDVI of Teak and Sal forests showed an increasing trend however, no trend was observed in seasonal and monthly NDVI over the same period. The maximum and minimum NDVI was found in the post-monsoon months (ON) and summer months (MAM) respectively. As STR is a Teak and Sal dominated landscape, the findings of the current study can also be applied in developing silvicultural and adaptation strategies for other Teak and Sal dominated landscapes of central India.

R. C. Hasan, Q. A. Rosle, M. A. Asmadi et al.

One of the most critical steps towards landslide risk analysis is the determination of element at risk. Element at risk describes any object that could potentially fail or exposed to hazards during disaster. Without quantification of element at risk information, it is difficult to estimate risk. This paper aims at developing a methodology to extract and quantity element at risk from airborne Light Detection and Ranging (LiDAR) data. The element at risk map produced was then used to construct exposure map which describes the amount of hazard for each element at risk involved. This study presented two study sites at Kundasang and Kota Kinabalu in Sabah with both areas have experienced major earthquake in June 2015. The results show that not all the features can be automatically extracted from the LiDAR data. For example, automatic extraction process could be done for building footprint and building heights, but for others such as roads and vegetation areas, a manual digitization is still needed because of the difficulties to differentiate between these features. In addition to this, there were also difficulties in identifying attribute for each feature, for example to separate between federal roads with state and unpaved roads. Therefore, for large area hazard and risk mapping, the authors suggested that an automatic process should be investigated in the future to reduce time and cost to extract important features from LiDAR data.

Carlos Mateo, Pedro L. Carro, Paloma Garcia-Ducar et al.

This article proposes the linearization of an intensity modulation/direct detection radio-over-fiber (RoF) link with feedback loop. The goal is to carry out the predistortion process in a real scenario, in which the output signals are a few kilometers far from the baseband unit (BBU). First, the feedback loop is considered ideal, so the output signals are captured at the remote radio head side. Then, the feedback loop is taken into account, and both the input and output signals are captured at the BBU side. Applying optimization algorithms, such as Fibonacci, Golden, or Powell, it is possible to seek the optimal attenuation value within only a few iterations, which minimizes the distortion of the feedback loop. Experiments are carried out in a RoF system with 10 and 25 km length fiber within the long-term evolution (LTE) standard. Measured results show how with a proper choice of the attenuation it is possible to reach analogous results regarding to an ideal feedback loop in terms of adjacent channel power ratio, the output signal power and error vector magnitude.

Youngwoong Kim, Myoung Jin Kim, Byung Sup Rho et al.

We report a noble coherent optical frequency domain reflectometry (OFDR) system that simply enables measurement range enhancement up to full coherence length of a laser source. The proposed technique is based on bidirectional determination of Rayleigh backscattered signal along a fiber. To do this, complex OFDR signals are acquired with the help of <inline-formula><tex-math notation="LaTeX">$\pi / 2$</tex-math></inline-formula> phase-shifting interferometry in a detection part and an additional delay fiber in a reference arm. Through a bidirectional determination process using the complex OFDR signals, mirrored signals appearing at both sides of the spatial domain were completely discriminated, so that ambiguity arising due to a positional origin can be removed. Bidirectional distributed strain and temperature sensing is successfully performed for the first time. Spectral shifts by applying strain to and heating of the test fiber were found to be independent on both sides of the reference position, indicating that twofold enhancement of the measurement range can be obtained compared to previous systems.

Pan Wang, Xiaosheng Xiao, Philippe Grelu et al.

In mode-locked thulium soliton fiber lasers, we experimentally observe and numerically confirm the formation of numerous dispersive-wave sidebands, following a bifurcation of the pulse dynamics into a stationary short-period pulsation. These resonant sidebands appear in addition to the Gordon&#x2013;Kelly sidebands that are formed in the stationary mode-locked regime. The origin of these sidebands is discussed, highlighting their complexity that does not comply with a simple modulation instability analysis.

E. Nocerino, F. Lago, D. Morabito et al.

During the last two decades we have witnessed great improvements in ICT hardware and software technologies. Three-dimensional content is starting to become commonplace now in many applications. Although for many years 3D technologies have been used in the generation of assets by researchers and experts, nowadays these tools are starting to become commercially available to every citizen. This is especially the case for smartphones, that are powerful enough and sufficiently widespread to perform a huge variety of activities (e.g. paying, calling, communication, photography, navigation, localization, etc.), including just very recently the possibility of running 3D reconstruction pipelines. The REPLICATE project is tackling this particular issue, and it has an ambitious vision to enable ubiquitous 3D creativity via the development of tools for mobile 3D-assets generation on smartphones/tablets. This article presents the REPLICATE project’s concept and some of the ongoing activities, with particular attention being paid to advances made in the first year of work. Thus the article focuses on the system architecture definition, selection of optimal frames for 3D cloud reconstruction, automated generation of sparse and dense point clouds, mesh modelling techniques and post-processing actions. Experiments so far were concentrated on indoor objects and some simple heritage artefacts, however, in the long term we will be targeting a larger variety of scenarios and communities.

P. Ribes-Pleguezuelo, B. Septriani, S. Zhang et al.

Abstract Background Low-stress soldering techniques can guarantee a minimized input of thermal energy allowing for the design and later assembly of more robust and miniaturized optical devices. However, in order to build miniaturized optical devices, these small-induced stresses produced by soldering techniques have to be investigated to guarantee that the stress-induced birefringence effects do not alter the device optical properties and requirements. Methods An analytical method that relates the stress-induced birefringence of laser components with their corresponding lasing capabilities has been compared to the real induced-stress results created in components packaged using solderjet technology. The main goal was to optimize the optical component packaging by using this low induced-stress soldering technique. The optimization was carried out by assessing components miniaturization while still assuring high robustness of the bond strength without creating a beam depolarization ratio of more than 1%. Results The outcome of the study showed the possibility of assembling laser optical components down to sizes of around 300 μm, creating a bond strength of 5 N and higher, and a depolarization ratio much lower than the proposed target of 1%. Conclusions Our results in terms of induced stress agreed with the finite element method result, which would imply correct post-processing laser simulations. This suggested that the solderjet bumping technique could robustly join components down to the laser emission beam size without strongly affecting the optical properties.

G. Wang

National administration of surveying, mapping and geoinformation started to launch the project of national fundamental geographic information database dynamic update in 2012. Among them, the 1:50000 database was updated once a year, furthermore the 1:250000 database was downsized and linkage-updated on the basis. In 2014, using the latest achievements of 1:250000 database, comprehensively update the 1:1000000 digital line graph database. At the same time, generate cartographic data of topographic map and digital elevation model data. This article mainly introduce national 1:1000000 cartographic data of topographic map, include feature content, database structure, Database-driven Mapping technology, workflow and so on.

D. Bulatov, I. Wayand, H. Schilling

In this paper, a new procedure for individual tree detection and modeling is presented. The input of this procedure consists of a normalized digital surface model NDSM, and a possibly error-prone classification result. The procedure is modular so that the functionality, the advantages and the disadvantages for every single module will be explained. The most important technical contributions of the paper are: Employing watershed transformation combined with classification results, applying hotspots detectors for identifying treetops in groups of trees, and correcting NDSM by detecting and geometric reconstruction of small anomalies, such as earth walls. Two minor contributions are made up by a detailed literature research on available methods for individual tree detection and estimation of tree-crowns for clearly identified trees in order to reduce arbitrariness by assigning trees to one of the few types in the output model.