Hasil untuk "Applied optics. Photonics"

Guanying Wang, Xianfeng Liang, Ning Zhang et al.

In smart grids, the magnetic sensors encounter reliability issues due to transient electromagnetic interference (EMI) and elevated temperature. In this work, we employed the finite-element method to simulate the reliability of current sensors used in gas-insulated substations under strong EMI and high temperature. By utilizing a damped oscillatory wave as the excitation source, the effect of the copper shielding layer on the induced electromagnetic field in the sensor chip was analyzed through simulation. We found that the induced electromagnetic field responses at the chip and bonding wires exhibit damped oscillatory waves as the excitation source. Interestingly, the intensity of induced electromagnetic field is substantially reduced by introducing the copper shielding layer, indicating effective anti-EMI. The thermal stress–strain simulation shows that the severe stress concentration (310.31 MPa) occurred at the bonding interfaces due to mismatch of the coefficients of thermal expansion. We design a cavity-integrated packaging structure that can reduce the stress by 74.6% and the wire deformation by 32.4%. To diminish both the EMI and the thermal stress/strain, a novel packaging structure consisting of a 3D-printed resin framework filled with electromagnetic shielding materials is proposed. This work provides useful guidance for the packaging design to improve the reliability of magnetic sensors in smart grids.

Huangcheng Shangguan, H. Paul Urbach, Jeroen Kalkman

Lensless single-shot dual-wavelength digital holography is resolution limited by the pixel-size of the camera and often has an insufficient depth range. We present a novel dual-wavelength holographic configuration with expanding wavefront illumination that breaks the pixel-limited resolution barrier and achieves diffraction-limited spatial resolution. By implementing expanding wavefront illumination with dual-wavelength digital holography based on a wavelength-tunable laser, we achieve a high-resolution centimeter-scale depth range. A quantitative precision analysis demonstrates that single-shot acquisition reaches the shot-noise-limited depth detection. The proposed holographic scheme provides a robust 3D optical inspection solution for high-throughput, micro-scale resolution industrial inline metrology.

I. Ahmed, U. K. Sharma, P. K. Garg et al.

Understanding building material properties can play a key role in analyzing the health of structural elements in buildings. However, the field and laboratory tests can be laborious, time-consuming, and cost-intensive. Generally, the standard tests employed for characterizing the material properties are destructive in nature, but in the recent past, non-destructive testing (NDT) has given us the ease of understanding the material properties. Hyperspectral remote sensing technology has been exploited as one of the NDT methods for assessing the properties of building components. This study aims to investigate the quality information about cement using the hyperspectral remote sensing method and correlate it with the results of traditional quality testing methods. The materials used in the experiments included Ordinary Portland Cement (OPC), Portland Pozzolana Cement (PPC), and White Portland Cement (WPC). The cement samples were studied and experimented with for the identification of their types, and their temporal variability and changes in their spectral properties on which the strength of the samples depended were further checked. The study concluded that for OPC, PPC, and WPC, the absorption range is 1970 nm to 2020 nm, which is mainly due to the presence of different chemical compounds in cement. Also, the spectral reflectance decreases with time, and it can be concluded that in the present work, the strength of cement decreases with the decrease in spectral reflectance. Hence, Cement properties can be found using hyperspectral remote sensing data.

Ilia Geints, Olga Kosareva

Previous studies of formation of extremely compressed wave packets during femtosecond filamentation in the region of anomalous group velocity dispersion in solid dielectrics mostly considered the case of linearly polarized laser pulses. However, recent results suggest potential applications of polarization state manipulation for ultrafast laser writing of optical structures in bulk solid-state media. In the present work, evolution of radiation polarization parameters during formation of such extreme wave packets at the pump wavelength of 1900 nm in fused silica is studied numerically on the basis of the carrier-resolved unidirectional pulse propagation equation (UPPE). It was revealed that initial close-to-circular polarization leads to higher intensity of the anti-Stokes wing in the spectrum of the generated supercontinuum. Numerical simulations indicate a complex, space–time variant polarization state, and the resulting spatiotemporal electric field distribution exhibits a strong dependence on the initial polarization of the femtosecond pulse. At the same time, electric field polarization tends to linear one in the region with the highest field strength regardless of the initial parameters. The origin of this behavior is attributed to the properties of the supercontinuum components generation during filament-induced plasma formation.

V. Longhi, A. Martino, A. M. Lingua et al.

Globalisation has contributed to rapid economic growth but has also exposed vulnerabilities such as the spread of pests in agriculture. An example is the <em>Popillia Japonica Newman</em> beetle, introduced to Italy in 2014, which has caused significant economic losses, mainly affecting vine cultures. Reliable identification of pests is essential for its management, but it is time-consuming and laborious. This has prompted growing interest in image-based methods, supported by computer vision (CV), which can significantly improve efficiency in insect detection. This study aims to evaluate a CV algorithm's effectiveness in identifying adult specimens of <em>Popillia</em> using Near-Infrared sensors on Uncrewed Aerial Systems (UAS). The project, conducted in two vineyards in northern Italy, intends to establish a replicable and standardised data acquisition protocol for future monitoring activities. Insects detected by the CV-based method are validated by manual counting performed by entomologists. In a GIS environment, prescription maps are generated in near real-time to identify where the vineyard is most affected and to guide the drone spraying treatment only on the areas in which the threshold is exceeded. The study demonstrates effective semi-automated monitoring, with a clear correlation between CV-based and manual insect measurements, as indicated by the Pearson correlation coefficients ranging from 0.89 to 0.96. Although the CV-based method may overestimate insect numbers, it provides valuable insights for targeted pest management interventions and damage assessment. The project outcomes offer a promising approach to safeguarding agriculture against invasive species, enhancing regional economic resilience while minimising the spread of insecticide, the required time, and human interaction with harmful substances.

R. Xue, R. Xue, R. Xue et al.

Single-photon detectors, with their exceptional sensitivity, provide a reliable means for single-photon-level detection, demonstrating significant advantages in detecting weak signals in complex environments compared to traditional detectors. With the continuous advancement in semiconductor manufacturing technology, single-photon detectors based on linear array configurations have emerged and rapidly developed. This study utilizes a linear array single-photon detector in free-running mode combined with a scanning mechanism to design and implement a spectral detection and imaging system. Through the spectral scanning unit, this system successfully achieves precise spectral detection in the 890 nm to 1710 nm range, with a spectral resolution better than 2 nm. Utilizing the imaging scanning unit, the system effectively performs target spectral imaging under single and multiple wavelength conditions at 1064 nm, 1310 nm, and 1520 nm. By optimizing algorithms for data processing, the system can achieve rapid and accurate spectral detection and imaging even under low-light conditions where the average photon count per pixel is less than 3. The results of this study are expected to provide strong technical support for the application of spectral imaging technology in the field of high-speed detection and imaging.

Yao Ji, Wensheng Chen, Danning Wang et al.

Atmospheric turbulence causes transmitted light to fade randomly, which results in irradiance scintillation fluctuations in the received signal and significantly affects the quality of wireless optical communication systems. In this paper, we investigate the propagation characteristics of a monochromatic light-emitting diode (LED) light beam through weak-to-strong turbulence. Considering the spatial incoherence of a monochromatic LED light source, the emitted light field of a monochromatic LED light source is represented by a random field multiplied by a deterministic field that follows a Gaussian distribution. Then, based on the extended-Rytov theory, a closed expression for the irradiance scintillation index under weak-to-strong turbulence is derived. In addition, the expression for the fading probability governed by the Gamma–Gamma model is given. Finally, the effects of near-earth atmospheric refractive index structural parameters, signal propagation distances, and working light wavelengths on propagation characteristics of the LED-based VLC system are simulated and compared with those of the laser-based one. The results theoretically confirm that laser light sources are more susceptible to atmospheric turbulence along the propagation path than monochromatic LED light sources. The investigation in this paper can provide theoretical support for the design of visible light communication systems in practical applications.

Martin Montagnac, Yoann Brûlé, Aurélien Cuche et al.

Abstract Light emission of europium (Eu3+) ions placed in the vicinity of optically resonant nanoantennas is usually controlled by tailoring the local density of photon states (LDOS). We show that the polarization and shape of the excitation beam can also be used to manipulate light emission, as azimuthally or radially polarized cylindrical vector beam offers to spatially shape the electric and magnetic fields, in addition to the effect of silicon nanorings (Si-NRs) used as nanoantennas. The photoluminescence (PL) mappings of the Eu3+ transitions and the Si phonon mappings are strongly dependent of both the excitation beam and the Si-NR dimensions. The experimental results of Raman scattering and photoluminescence are confirmed by numerical simulations of the near-field intensity in the Si nanoantenna and in the Eu3+-doped film, respectively. The branching ratios obtained from the experimental PL maps also reveal a redistribution of the electric and magnetic emission channels. Our results show that it could be possible to spatially control both electric and magnetic dipolar emission of Eu3+ ions by switching the laser beam polarization, hence the near field at the excitation wavelength, and the electric and magnetic LDOS at the emission wavelength. This paves the way for optimized geometries taking advantage of both excitation and emission processes.

Graeme E. Johnstone, Johannes Herrnsdorf, Martin D. Dawson et al.

Challenging imaging applications requiring ultra-short exposure times or imaging in photon-starved environments can acquire extremely low numbers of photons per pixel, (<1 photon per pixel). Such photon-sparse images can require post-processing techniques to improve the retrieved image quality as defined quantitatively by metrics including the Structural Similarity Index Measure (SSIM) and Mean Squared Error (MSE) with respect to the ground truth. Bayesian retrodiction methods have been shown to improve estimation of the number of photons detected and spatial distributions in single-photon imaging applications. In this work, we demonstrate that at high frame rates (>1 MHz) and low incident photon flux (<1 photon per pixel), image post processing can provide better grayscale information and spatial fidelity of reconstructed images than simple frame averaging, with improvements in SSIM up to a factor of 3. Various other image post-processing techniques are also explored and some of which result in a similar quality of image reconstruction to Bayesian retrodiction, with lower computational load. Image reconstructions using Bayesian Retrodiction or bilateral filtering are of comparable quality to frame averaging, as measured by the Structural Similarity Index Measure, when using less than 40% of the photon flux.

Stanisław Kurzyna, Marcin Jastrzębski, Nicolas Fabre et al.

Despite the multitude of available methods, the characterisation of ultrafast pulses remains a challenging endeavour, especially at the single-photon level. We introduce a pulse characterisation scheme that maps the magnitude of its short-time Fourier transform. Contrary to many well-known solutions it does not require nonlinear effects and is therefore suitable for single-photon-level measurements. Our method is based on introducing a series of controlled time and frequency shifts, where the latter is performed via an electro-optic modulator allowing a fully-electronic experimental control. We characterized the full spectral and temporal width of a classical and single-photon-level pulse and successfully reconstructed their spectral phase and amplitude. The method can be extended by implementing a phase-sensitive measurement and is naturally well-suited to partially-incoherent light.

Zhanghang Zhu, Di Zhang, Fei Xie et al.

Zhanghang Zhu†,1 Di Zhang†,1 Fei Xie, Jiaxin Chen, Shengchao Gong, Wei Wu, Wei Cai, Xinzheng Zhang, Mengxin Ren, 2, a) and Jingjun Xu b) The Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, School of Physics and TEDA Applied Physics Institute, Nankai University, Tianjin, 300071, P.R. China Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, P.R. China

Fabio Marangi, Matteo Lombardo, Andrea Villa et al.

The endeavor of the scientific community to maximize the possibility to harvest Sun irradiation for energy production is mainly devoted to the improvement of the power conversion efficiency of devices and to the extension of the spectral range in which solar devices operate. Considering that a significant portion of the Sun irradiation at the ground level is in the infrared, the research on materials and systems that operate in such region is gaining increasing attention. In this review, we will report recent advancements in multijunction solar cells, inorganic-organic perovskite solar cells, organic solar cells, colloidal quantum dot solar cells focusing on the absorption of such devices in the infrared. In addition, the use of upconverting nanostructures will be introduced as a way to indirectly exploit infrared radiation to increase power conversion efficiency of photovoltaic devices. Moreover, we will describe plasmon induced hot electron extraction based solar cells, that are particularly promising in absorbing the infrared portion of the Sun irradiation when the active materials are doped semiconductors, which show intense plasmonic resonances in the infrared. The review includes the optical spectroscopy tools to study the hot electron extraction from doped semiconductor-based heterojunctions.

Yang Qi, Ben Wu

We design and experimentally demonstrate a radio frequency interference management system with free-space optical communication and photonic signal processing. The system provides real-time interference cancellation in 6 GHz wide bandwidth.

Zhibing Liu, Jiahui Zou, Zhaoyu Lai et al.

Optical coordinate transformation (OCT) has attracted widespread attention in the field of orbital angular momentum (OAM) (de)multiplexing or manipulation, but the performance of OCT would suffer from its distortion. In this paper, we quantitatively analyze the distortion of OCT from the perspective of ray optics, and explain its rationality to work under non-normal incident light. For the special case of log-polar coordinate transformation (LPCT), we use a raytracing assisted optimization scheme to improve its distortion, which is related to a Zernike polynomial based phase compensation. After raytracing optimization, the root mean square error (RMSE) of the focused rays is reduced to 1/5 of the original value and the physical optic simulation also shows great improvement. In the experiment, we use three phase masks which are realized by metasurfaces, the measured results show well consistency with the simulation. Results in this paper have great potential to improve the performance of OCT related applications.

M. Mansuripur

This paper contains a transcript of my presentation at the Wyant Tribute Symposium on August 2, 2021 at SPIE’s Optics and Photonics conference in San Diego, California. The technical part of the paper has no overlap with a previous article of mine that was published in Applied Optics last year, bearing the same title as this one. The applications of Fourier transformation described in the present paper include the central limit theorem of probability and statistics, the Shannon-Nyquist sampling theorem, and computing the electromagnetic field radiated by an oscillating magnetic dipole.

G. Q. Ngo, Emad Najafidehaghani, Ziyang Gan et al.

Gia Quyet Ngo, Emad Najafidehaghani, Ziyang Gan, Sara Khazaee, Antony George, Erik P. Schartner, Heike Ebendorff-Heidepriem, Thomas Pertsch, Alessandro Tuniz, Markus A. Schmidt, Ulf Peschel, Andrey Turchanin, and Falk Eilenberger Institute of Applied Physics, Abbe Center of Photonics, Friedrich Schiller University Jena, Albert-Einstein-Str. 15, 07745 Jena, Germany Institute of Physical Chemistry, Abbe Center of Photonics, Friedrich Schiller University Jena, Lessingstraße 10, 07743 Jena, Germany Institute of Solid State Theory and Optics, Abbe Center of Photonics, Friedrich Schiller University Jena, Max-Wien-Platz 1, 07743 Jena, Germany ARC Centre of Excellence for Nanoscale BioPhotonics (CNBP), Institute for Photonics and Advanced Sensing, School of Physical Sciences, University of Adelaide, Adelaide SA 5005, Australia Fraunhofer-Institute for Applied Optics and Precision Engineering IOF, Albert-Einstein-Str. 7, 07745 Jena, Germany Max Planck School of Photonics, Germany Institute of Photonics and Optical Science (IPOS) and university of Sydney Nano Institute (Sydney Nano), School of Physics, The University of Sydney, Camperdown, NSW 2006, Australia Leibniz Institute of Photonic Technology (IPHT), Albert-Einstein-Str. 9, 07745 Jena, Germany

Feng Chen, Yuping Chen

Lithium niobate (LiNbO3), so-called “Silicon in Photonics,” is a multifunctional crystal with a combination of a number of excellent physical properties. In optics and photonics, the LiNbO3-based devices, such asmodulators, wavelength converters, waveguide amplifiers, and quantum photonic chips, have been realized and widely applied in various areas. In addition to the traditional waveguides, the LiNbO3 on insulators (LNOI) technology enables fabrication of large-scale, high-quality LiNbO3 thin film wafers, boosting the development of thin film LiNbO3-based devices; consequently, versatile applications have been realized to satisfy the small footprint for photonic integrated circuits (PICs). Aiming to present the impressive progresses in this field, Chinese Optics Letters publishes this special issue focusing on the fabrication of new LNOI wafers, new design of LNOI-based structures, and the intriguing applications of LNOI-based devices in selected active topics. This special issue includes 11 invited and 5 contributed papers by the active groups on LiNbO3-based photonic devices. The fabrication of new LNOI wafers is the base of high-performance functional devices. Hu et al. reported on the fabrication of new hybrid Si=LiNbO3 thin film platforms and investigated their properties. Zhao et al. studied the ridge waveguide fabrication in LiNbO3 by oxygen ion implantation and precise diamond dicing, which is helpful to understand the ion–lattice interaction process (also being a fundamental of LNOI wafer fabrication). The experimental techniques for characterization of LNOI-based devices are crucial for their applications. Luo et al. demonstrated the polarization diversity of a two-dimensional grating coupler on x-cut LNOI. One of the major applications of LNOI-based photonic devices is to realize nonlinear frequency conversion, for example, second harmonic generation (SHG). In this special issue, nonlinear LNOI devices have been presented as follows. Lu et al. reviewed the advances of SHG based on the thin film LiNbO3 platform, summarizing the up-to-date progress of nonlinear LNOI devices for integrated photonic applications. Xie et al. studied the effect of dimension variation for LNOI waveguides towards SHG, indicating that the SHG profile and efficiency can be greatly affected by the waveguide cross-section dimension variations. Li et al. theoretically proposed a Si-covered LNOI waveguide structure for highly efficient SHG, which may be useful to design new types of LNOI wafers. Hu et al. reported on local periodically poled LNOI ridge waveguides for SHG, and up to normalized conversion efficiency of 435.5%W−1· cm−2 was obtained. In addition to the typical nonlinear optical effects, Sheng et al. investigated nonlinear Talbot self-healing in periodically poled LiNbO3 crystals, opening up new possibilities for defect-tolerant optical lithography and printing. Li et al. reported on the direct generation of vortex beams in the second harmonic by a spirally structured fundamental wave. Modulators are typical photonic devices. The configurations of the LNOI-based modulators are multiple. In this special issue, Cai et al. reported on an integrated thin film LiNbO3 modulator based on Fabry–Perot geometry, and Liu et al. realized a wideband thin film LiNbO3 modulator with low half-wave-voltage length product of only 1.7 V·cm based on the Mach–Zehnder configuration. Moreover, Fang et al. produced high-quality-factor optical racetrackmicro-resonators (intrinsicQ factor∼2.8 × 106) based on LNOIs with an electro-optical tuning range spanning over one free spectral range of 86 pm. Wang et al. demonstrated LiNbO3 microring resonators with intrinsic Q factors over 105 using standard lift-off metallic masks and dry etching, which was considered as a fully compatible process with wafer-scale production. In addition to the above devices, Bo et al. reported on the fabrication of on-chip erbium-doped LNOI waveguide amplifiers, and a net internal gain of ∼30 dB=cm in the telecommunication band was achieved. Jia et al. proposed LNOI-based dielectric metasurfaces to realize surface lattice resonances for enhanced light–matter interaction, offering valuable information for the design and optimization of high-quality-factor optical LiNbO3 metasurfaces. Ge et al. theoretically constructed a broadband and lossless valley photonic crystal waveguide robust against sharp bend and chirality in LiNbO3 valley photonic crystals. This work can provide guidance on the design of the high-performance topological waveguides with a lossless edge state for low refractive index materials. It is noted that the commercialization of the LNOI wafer has sparked significant on-chip photonic integration requirements in the past five years. To provide a common platform compatible with Si photonics, Hu et al. explored and fabricated the heterogeneous integration of Si and LiNbO3 thin films of 3 inch wafers, which combines the advantages of excellent electric properties and mature semiconductor processing technology of Si, as well as the remarkable photonic, acousto-optic, electro-optic, and piezoelectric nature of LiNbO3. The Si-LNOI wafer will drive new promising devices and potential applications for PICs. Vol. 19, No. 6 | June 2021

D. Englund

Photonic integrated circuits (PICs) have become increasingly important in classical communications applications over the past decades, including as transmitters and receivers in long-haul, metro and datacenter interconnects. Many of the same attributes that make PICs attractive for these applications — compactness, high bandwidth, and the ability to control large numbers of optical modes with high phase stability — also make them appealing for quantum information processing. Here we review our recent progress in developing PICs for quantum information processing. The first part of the talk will describe architectures for programmable PIC that can be programmed to implement arbitrary unitary linear-optics transformations. We recently applied these chips to applications ranging from deep neural networks​1 to quantum transport simulations​2​, but this talk will focus on recent advances in entangled photon sources​3 and proposals for on-demand single photon sources​4​, photon-photon nonlinear interactions, and neural neural network processors​5​. The second part of the talk will consider new PIC platforms that can be integrated directly with atom-like quantum memories. In particular, we will discuss PICs based on the AlGaN-sapphire material system that are transparent in the UV-VIS spectrum, for applications in multiplexed quantum repeaters. This PIC platform now allows quality factors in excess of 20,000 for wavelengths as short as 369nm​6 and the integration of diamond nitrogen vacancy color centers and superconducting single-photon resolving detectors​7​. Finally, we describe a blueprint for scalable cluster-state quantum computing that builds on large numbers of cavity-coupled diamond color centers networked by photonic switches and waveguides​8​.

G. Lio, A. Ferraro, M. Giocondo et al.

This work presents numerical and experimental results of plasmonic Metal-Insulator optical nano-cavities. The systems are composed of Silver as metal, polyvinylpyrrolidone or indium tin oxide or zinc oxide as insulator. The proposed nano-cavities exhibit extraordinary effects as colors changing in function of the incident/view angles, enhancement of the experimental real and imaginary parts of the pseudo dielectric constant, an extraordinary transmission of 50$\%$ and zero reflection for both polarizations at the resonant wavelengths. These results lead to the formation and propagation of surface plasmon polaritons and their hybridization in gap surface plasmons. The concurrence of these effects allow studying the Goos-Hanchen shift by exploiting the very narrow $\Delta$ and $\Psi$ ellipsometer parameters. Thank to their optical properties, the proposed nano-cavities could be applied in several fields such tunable color filters, optics, photonics and sensing.

K. Möllmann, M. Regehly, M. Vollmer

Light emitting diodes and semiconductor lasers are key elements of photonic systems, and every student enrolled in applied optics or photonics programs at universities learns about their fundamental physics and applications. We present part of a laboratory course for students of a photonics Master’s program which complements theoretical lectures on these fundamental photonic components. During this course, students investigate diode lasers using four different techniques with emphasis on the transition from spontaneous emission (LED mode) to lasing action. The first two parts—recording diode characteristics of current versus voltage and output power versus current, as well as determining the spatial characteristics of the commercial diode lasers—are common in most similar laboratory courses. Here we focus on the remaining two investigations. On the one hand, diode laser dimensions are quantitatively analyzed using visible microscopy and also electron microscopy. This includes images of the laser chip during operation in LED or laser mode which allows us to gain an understanding of light propagation in and around the active layer waveguide. On the other hand, changes of the emission spectra while increasing the injection current from LED to laser operation are measured with high accuracy using a Fourier transform spectrometer. This allows determination of the longitudinal mode spacing, which is in very good agreement with intuitive, theoretical predictions, though parts of the analysis are surprising for many students.