Hasil untuk "Applied optics. Photonics"

Alán Aspuru-Guzik, P. Walther

Zhaoyi Li, R. Pestourie, Zin Lin et al.

: Conventional human-driven methods face limitations in designing complex functional metasurfaces. Inverse design is poised to empower metasurface research by embracing fast-growing arti fi cial intelligence. In recent years, many research e ff orts have been devoted to enriching inverse design principles and applications. In this perspective, we review most commonly used metasurface inverse design strategies including topology optimization, evolutionary optimization, and machine learning techniques. We elaborate on their concepts and working principles, as well as examples of their implementations. We also discuss two emerging research trends: scaling up inverse design for large-area aperiodic metasurfaces and end-to-end inverse design that co-optimizes photonic hardware and post-image processing. Furthermore, recent demonstrations of inverse-designed metasurfaces showing great potential in real-world applications are highlighted. Finally, we discuss challenges in future inverse design advancement, suggest potential research directions, and outlook opportunities for implementing inverse design in nonlocal metasurfaces, recon fi gurable metasurfaces, quantum optics, and nonlinear metasurfaces.

C. F. Mendes, V. Liesenberg, R. Q. Feitosa et al.

Araucaria angustifolia (Bertol.) Kuntze, an iconic and endemic species of the Mixed Ombrophilous Forest, plays a key ecological and economic role within the Atlantic Rainforest. However, it is currently threatened by historical overexploitation and its sensitivity to climate change. This study examines the application of deep learning for the automated detection of A. angustifolia individuals in high-resolution imagery collected by Unmanned Aerial Vehicle (UAV) at selected sites in Santa Catarina, Brazil. The YOLOv11x model, a state-of-the-art convolutional neural network (CNN) architecture, was trained using two distinct datasets: a heterogeneous set and a more homogeneous one, the latter evaluated with K-Fold cross-validation. Results showed that model performance improved with increased data uniformity, with average precision (AP) rising from 21% to 27% and the F1-score from 54% to 61%. While detection accuracy remains below optimal levels, the findings highlight the model's potential for species identification. Enhancements in annotation quality, dataset diversity, and hyperparameter optimization are recommended to improve performance further and support more robust monitoring and conservation efforts for A. angustifolia.

Junseok Heo, Chanwoong Wi, Nagarajan Chinnapaiyan et al.

Abstract Creating arbitrary-shaped 3D electrodes on all surfaces of electronic structures holds critical significance in semiconductor packaging, micro-displays and bio/chemical sensors for more precise, more reliable and higher density integration. Multi-step nature of the existing electronics patterning technologies, however, translates to increased cost and process complexity together with low design flexibility. Here, we introduce an ultrafast-laser-driven conductive thin-film deposition technique, enabling sub-micron-resolution patterning of conductive carbon electronics on all substrate surfaces. This method leverages the nonlinear absorption of ultrashort laser pulses, not to directly decompose the precursor, but to locally heat transparent quartz substrates. This localized, intense heating then triggers the decomposition of a gaseous precursor on the hot substrate surface, leading to the direct formation of laser-induced graphene (LIG). We demonstrate the ability to achieve tunable LIG morphology and electrical properties, including low sheet resistance, by precisely controlling laser parameters and reaction conditions. Crucially, this technique allows for the creation of intricate three-dimensional conductive patterns within transparent structures, opening up new avenues for the direct fabrication of integrated electronic components. This versatile approach holds significant promise for advanced applications in semiconductors, sensors, biotechnology, and microfluidics, offering a pathway to create functional electronic architectures with unprecedented spatial control in transparent structures.

Ileana-Cristina Benea-Chelmus, Sydney Mason, M. Meretska et al.

Electro-optic modulators are essential for sensing, metrology and telecommunications. Most target fiber applications. Instead, metasurface-based architectures that modulate free-space light at gigahertz (GHz) speeds can boost flat optics technology by microwave electronics for active optics, diffractive computing or optoelectronic control. Current realizations are bulky or have low modulation efficiencies. Here, we demonstrate a hybrid silicon-organic metasurface platform that leverages Mie resonances for efficient electro-optic modulation at GHz speeds. We exploit quasi bound states in the continuum (BIC) that provide narrow linewidth (Q = 550 at λres=1594\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\lambda }_{{{{{{{{\rm{res}}}}}}}}}=1594$$\end{document} nm), light confinement to the non-linear material, tunability by design and voltage and GHz-speed electrodes. Key to the achieved modulation of ΔTTmax=67%\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\frac{{{\Delta }}T}{{T}_{\max }}=67 \%$$\end{document} are molecules with r33 = 100 pm/V and optical field optimization for low-loss. We demonstrate DC tuning of the resonant frequency of quasi-BIC by Δλres=\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\Delta }}{\lambda }_{{{{{{{{\rm{res}}}}}}}}}=$$\end{document} 11 nm, surpassing its linewidth, and modulation up to 5 GHz (fEO,−3dB = 3 GHz). Guided mode resonances tune by Δλres=\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\Delta }}{\lambda }_{{{{{{{{\rm{res}}}}}}}}}=$$\end{document} 20 nm. Our hybrid platform may incorporate free-space nanostructures of any geometry or material, by application of the active layer post-fabrication. Active photonics in free space is important in computing, imaging and sensing. Here, hybrid silicon-organic nanoscale structures change the intensity of a free-space light beam by applied microwave signals at gigahertz speeds with a high efficiency.

Shunfeng Sheng, Hao Li, Yi Zhang et al.

Detecting electrolyte leakage is an effective early warning approach for abnormal faults in lithium-ion batteries (LIBs) and can help mitigate safety risks such as fires and explosions. However, detecting electrolyte leakage in the early stages of LIB faults presents a significant challenge, as leaks in LIBs produce volatile organic compounds (VOCs) at parts per million levels that are difficult to detect using conventional VOC sensors. Here, an effective LIB VOC sensor using micro-nano optical fibres (MNFs) has been developed for the first time, coated with an in situ self-assembled zeolitic imidazolate framework-8 (ZIF-8) membrane as an electrolyte-sensitive layer. The abundance of pores in ZIF-8 is excellent for adsorbing a variety of VOCs, including diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, and propylene carbonate. The MNFs possess high refractive index sensitivity, enhancing the online monitoring of electrolytes. MNFs with a diameter of approximately 7 μm were assembled with four-cycle ZIF-8 of approximately 500 nm thickness, as the fabricated sensor. Through wavelength demodulation, the LIB sensor demonstrated high sensitivity, detecting 43.6 pm/ppm of VOCs and exhibiting rapid response and recovery times of typically within 10 min and 23 s, respectively, as well as a low theoretical detection limit of 2.65 ppm for dimethyl carbonate vapor with excellent reversibility. The first on-site verification of online LIB leakage monitoring demonstrated that the sensor achieved a 35 h early warning prior to full-load leakage, thus exhibiting promising prospects for applications in scenarios such as car batteries.

Wenhao Wang, Long Wang, Qianqian Fu et al.

Color as an indispensable element in our life brings vitality to us and enriches our lifestyles through decorations, indicators, and information carriers. Structural color offers an intriguing strategy to achieve novel functions and endows color with additional levels of significance in anti-counterfeiting, display, sensor, and printing. Furthermore, structural colors possess excellent properties, such as resistance to extreme external conditions, high brightness, saturation, and purity. Devices and platforms based on structural color have significantly changed our life and are becoming increasingly important. Here, we reviewed four typical applications of structural color and analyzed their advantages and shortcomings. First, a series of mechanisms and fabrication methods are briefly summarized and compared. Subsequently, recent progress of structural color and its applications were discussed in detail. For each application field, we classified them into several types in terms of their functions and properties. Finally, we analyzed recent emerging technologies and their potential for integration into structural color devices, as well as the corresponding challenges.

Yin Kang, Zhen Wang, Kaiqing Zhang et al.

Precisely synchronized X-ray and strong-field coherent terahertz (THz) enable the coherent THz excitation of many fundamental modes (THz pump) and the capturing of X-ray dynamic images of matter (X-ray probe), while the generation of such a light source is still a challenge for most existing techniques. In this paper, a novel X-ray free-electron laser based light source is proposed to produce a synchronized high-powered X-ray pulse and strong field, widely frequency tunable coherent THz pulse simultaneously. The technique adopts a frequency beating laser modulated electron bunch with a Giga-electron-volt beam energy to generate an X-ray pulse and a THz pulse sequentially by passing two individual undulator sections with different magnetic periods. Theoretical analysis and numerical simulations are carried out using the beam parameters of the Shanghai soft X-ray free-electron laser facility. The results show that the technique can generate synchronized 4 nm X-ray radiation with a peak power of 1.89 GW, and narrow-band THz radiation with a pulse energy of 1.62 mJ, and the frequency of THz radiation can be continuously tuned from 0.1 to 40 THz. The proposed technique can be used for THz pump and X-ray probe experiments for dynamic research on the interaction between THz pulse and matter at a femtosecond time scale.

A. Murtiyoso, J. Markiewicz, A. K. Karwel et al.

The concept of Neural Radiance Fields (NeRF) emerged in recent years as a method to create novel synthetic 3D viewpoints from a set of trained images. While it has several overlaps with conventional photogrammetry and especially multi-view stereo (MVS), its main point of interest is the capability to rapidly recreate objects in 3D. In this paper, we investigate the quality of point clouds generated by state-of-the-art NeRF in the context of interior spaces and compare them to four conventional MVS algorithms, of which two are commercial (Agisoft Metashape and Pix4D) and the other two open source (Patch-Match and Semi-Global Matching). Three synthetic datasets of interior scenes were created from laser scanning data with different characteristics and architectural elements. Results show that NeRF point clouds could achieve satisfactory results geometrically speaking, with an average standard deviation of 1.7 cm in interior cases where the scene dimension is roughly 25–50 m³ in volume. However, the level of noise on the point cloud, which was considered as out of tolerance, ranges between 17–42%, meaning that the level of detail and finesse is most likely insufficient for sophisticated heritage documentation purposes, even though from a visualisation point of view the results were better. However, NeRF did show the capability to reconstruct texture less and reflective surfaces where MVS failed.

L. Rigutti, E. Di russo, P. Dalapati et al.

The laser pulses controlling the ion evaporation in Laser-assisted Atom Probe Tomography (La-APT) can simultaneously excite photoluminescence in semiconductor or insulating specimens [1]. An atom probe equipped with approriate focalization and collection optics can thus be coupled with an in-situ micro-photoluminescence (μPL) bench [2] that can be operated even during APT analysis. Our team has recently developed a coupled μPL-APT instrument operating at 400 kHz, controlled by 150 fs laser pulses tunable in energy in a large spectral range (spanning from deep UV to near IR). Micro-PL spectroscopy is performed using a 320 mm focal length spectrometer equipped with a CCD camera for time-integrated and with a streak camera for time-resolved acquisitions. Such a Photonic Atom Probe (PAP) has been applied to the study of the optical properties of nanoscale emitters in an in-situ correlative microscopy approach. The evolution of the PL signal during the APT analysis is an original source of information. In this work we analyzed specimens containing ZnO/(Mg,Zn)O quantum wells (QWs) of different thicknesses, and we show that it is possible to distinguish the optical signatures of separate QWs distant as few as 20 nm – well below the diffraction limit of the laser [3]. This information is then correlated with the chemical 3D distribution obtained by APT. The analysis of the PL spectral shifts during the APT analysis also allows determining the stress state induced by the electrostatic field [4].

Chong Sheng, Yao Wang, Yijun Chang et al.

Topology have prevailed in a variety of branches of physics. And topological defects in cosmology are speculated akin to dislocation or disclination in solids or liquid crystals. With the development of classical and quantum simulation, such speculative topological defects are well-emulated in a variety of condensed matter systems. Especially, the underlying theoretical foundations can be extensively applied to realize novel optical applications. Here, with the aid of transformation optics, we experimentally demonstrated bound vortex light on optical chips by simulating gauge fields of topological linear defects in cosmology through position-dependent coupling coefficients in a deformed photonic graphene. Furthermore, these types of photonic lattices inspired by topological linear defects can simultaneously generate and transport optical vortices, and even can control the orbital angular momentum of photons on integrated optical chips. Optical vortices in a topological defect of cosmic space-time.

Xuezhi Ma, Yuan Ma, Preston Cunha et al.

Mario Krenn, Jakob S. Kottmann, Nora Tischler et al.

P. Lombardi, M. Colautti, R. Duquennoy et al.

Single molecules in solid state matrices have been proposed as sources of single photon Fock states back 20 years ago. Their success in quantum optics and in many other research fields stems from the simple recipes used in the preparation of samples, with hundreds of nominally identical and isolated molecules. Main challenges as of today for their application in photonic quantum technologies are the optimization of light extraction and the on-demand emission of indistinguishable photons. We here present Hong–Ou–Mandel (HOM) experiments with photons emitted by a single molecule of dibenzoterrylene in an anthracene nanocrystal at 3 K, under continuous wave and also pulsed excitation. A detailed theoretical model is applied, which relies on independent measurements for most experimental parameters, hence allowing for an analysis of the different contributions to the two-photon interference visibility, from residual dephasing to spectral filtering. A HOM interference visibility of more than 75% is reported, which, according to the model, is limited by the residual dephasing present at the operating temperature.

S. Haque, M. Alexandre, M. Mendes et al.

Abstract Photonic micro/nano-structures in the wave-optics regime have shown to be a promising strategy for effective broadband light capture in ultra-thin devices, opening a window of opportunity for cheap, efficient, lightweight and flexible photovoltaics (PV). Here we design, from an optical standpoint, a novel industrially-attractive concept where light trapping is obtained by conformably depositing the solar cell materials onto previously-patterned photonic substrates. This solution is applied and optimized for perovskite solar cells (PSCs) with distinct thicknesses of the perovskite absorber - the conventional (500 nm) and ultra-thin (300 nm) in view of enhanced flexibility - yielding photocurrent improvements up to 22.8% in superstrate cell configuration and 24.4% in substrate-type configuration; thereby coming relatively close to the fundamental Lambertian limits. Furthermore, these structures also show an omni-direction optical response for incidence angles up to 70° for all cases, therefore demonstrating the viability of this light trapping method for implementation in flexible PV devices operating under bending. The photonic-enhanced ultra-thin solar cells designed here ultimately support the reduction of material usage in PSC technology, which is especially beneficial to mitigate lead usage, without impacting the device's performance.

O. Morozov, A. Sakhabutdinov

The article describes the theory and technique of addressed fiber Bragg structures and a new class of microwave-photonic sensory systems based thereon, the distinctive feature of which is that the fiber Bragg structure forms two ultra-narrowband frequency components separated by a unique address frequency spacing. The offset of the central frequencies of the Bragg structures is determined via processing a beat signal of the address frequencies on the photodetector, with its parameters making it possible to evaluate the physical fields applied. We formulate and solve a problem of unambiguously determining the central (Bragg) frequency shift of the addressed fiber Bragg structures with unique address frequencies and the same Bragg frequency. These are then combined into a single multi-sensor system with multiplexed response reception on a single photodetector.

G. An, X. Hao, Shuguang Li et al.

H. J. Qiao, H. J. Qiao, X. Wan et al.

Real-time change detection and analysis of natural disasters is of great importance to emergency response and disaster rescue. Recently, a number of video satellites that can record the whole process of natural disasters have been launched. These satellites capture high resolution video image sequences and provide researchers with a large number of image frames, which allows for the implementation of a rapid disaster procedure change detection approach based on deep learning. In this paper, pixel change in image sequences is estimated by optical flow based on FlowNet 2.0 for quick change detection in natural disasters. Experiments are carried out by using image frames from Digital Globe WorldView in Indonesia Earthquake took place on Sept. 28, 2018. In order to test the efficiency of FlowNet 2.0 on natural disaster dataset, 7 state-of-the-art optical flow estimation methods are compared. The experimental results show that FlowNet 2.0 is not only robust to large displacements but small displacements in natural disaster dataset. Two evaluation indicators: Root Mean Square Error (RMSE) and Mean Value are used to record the accuracy. For estimation error of RMSE, FlowNet 2.0 achieves 0.30 and 0.11 pixels in horizontal and vertical direction, respectively. The error in horizontal error is similar to other algorithms but the value in vertical direction is significantly lower than them. And the Mean Value are 1.50 and 0.09 pixels in horizontal and vertical direction, which are most close to the ground truth comparing to other algorithms. Combining the superiority of computing time, the paper proves that only the approach based on FlowNet 2.0 is able to achieve real-time change detection with higher accuracy in the case of natural disasters.

M. Foster, A. C. Turner, M. Lipson et al.

We review recent research on nonlinear optical interactions in waveguides with sub-micron transverse dimensions, which are termed photonic nanowires. Such nanowaveguides, fabricated from glasses or semiconductors, provide the maximal confinement of light for index guiding structures enabling large enhancement of nonlinear interactions and group-velocity dispersion engineering. The combination of these two properties make photonic nanowires ideally suited for many nonlinear optical applications including the generation of single-cycle pulses and optical processing with sub-mW powers.

F. Mondain, T. Lunghi, A. Zavatta et al.

We demonstrate a squeezing experiment exploiting the association of integrated optics and telecom technology as key features for compact, stable, and practical continuous variable quantum optics. In our setup, squeezed light is generated by single pass spontaneous parametric down conversion on a lithium niobate photonic circuit and detected by an homodyne detector whose interferometric part is directly integrated on the same platform. The remaining parts of the experiment are implemented using commercial plug-and-play devices based on guided-wave technologies. We measure, for a CW pump power of 40 mW, a squeezing level of -2.00$\pm$0.05 dB, thus confirming the validity of our approach and opening the way toward miniaturized and easy-to-handle continuous variable based quantum systems.