Hasil untuk "Applied optics. Photonics"

Shivasubramanian Gopinath, Joseph Rosen, Vijayakumar Anand

Fresnel incoherent correlation holography (FINCH) is a self-interference-based incoherent digital holography method. In FINCH, light from an object point is split into two beams, modulated differently using two lenses with different focal distances, and creates a self-interference hologram. At least three phase-shifted holograms are recorded and synthesized into a complex hologram, which reconstructs the object image without twin image and bias noises. Compared with conventional imaging, FINCH exhibits a longer depth of focus (DOF) and higher lateral resolution. In this study, we propose and demonstrate a new method termed post-engineering of axial resolution in FINCH (PEAR-FINCH), which enables post-recording DOF engineering for the first time. In PEAR-FINCH, a library of FINCH holograms catalogued with unique axial characteristics, DOF, and focus location is recorded by changing the focal distance of one of the diffractive lenses. Selected holograms from this library are combined to engineer new axial characteristics not achievable in FINCH. A two-step reconstruction, involving numerical back-propagation and deconvolution with a point spread hologram, is implemented. Experiments with multiplane objects having large axial separations confirm that PEAR-FINCH achieves a substantially extended DOF compared with direct imaging and FINCH. PEAR-FINCH will be promising for applications in biomedical imaging, holography, and fluorescence microscopy.

Feng Zhou

ABSTRACT The authors theoretically report a plasmonic photodetector based on graphene‐black phosphorus heterostructure which is capable of operating from visible to mid‐infrared (MIR) wavelengths. The combination of plasmonic nanostructure and graphene‐black phosphorus heterostructure can significantly enhance the absorption, simulation results show that the proposed photodetector is capable of working from 400 nm to 3 μm with ultrahigh responsivity all exceeding 14,000 AW−1 and large modulation bandwidth all over 327 GHz. In addition, by utilising the evident anisotropic characteristics of black phosphorus, the broadband plasmonic photodetector exhibits the angle‐dependent responsivity which can be used to design the customised plasmonic photodetector. The authors believe that the proposed photodetector would provide the new approach to design the broadband and angle‐dependent optoelectronic devices based on 2D materials.

D. Morrill, W. Hettel, D. Carlson et al.

High-harmonic upconversion driven by a mid-infrared femtosecond laser can generate coherent soft x-ray beams in a tabletop-scale setup. Here, we report on a compact ytterbium-pumped optical parametric chirped pulse amplifier (OPCPA) laser system seeded by an all-fiber front-end and employing periodically poled lithium niobate (PPLN) nonlinear media operated near the pulse fluence limits of current commercially available PPLN crystals. The OPCPA delivers 3 µm wavelength pulses with 775 µJ energy at 1 kHz repetition rate, with transform-limited 120 fs pulse duration, diffraction-limited beam quality, and ultrahigh 0.33% rms energy stability over >18 h. Using this laser, we generate soft x-ray high harmonics (HHG) in argon gas by focusing into a low-loss, high-pressure gas-filled anti-resonant hollow core fiber (ARHCF), generating coherent light at photon energies up to the argon L-edge (250 eV) and carbon K-edge (284 eV), with high beam quality and ∼1% rms energy stability. This work demonstrates soft x-ray HHG in a high-efficiency guided-wave phase matched geometry, overcoming the high losses inherent to mid-IR propagation in unstructured waveguides, or the short interaction lengths of gas cells or jets. The ARHCF can operate in the long term without damage and with the repetition rate, stability, and robustness required for demanding applications in spectromicroscopy and imaging. Finally, we discuss routes for further optimizing the soft x-ray HHG flux by driving He at higher laser intensities using either the signal (1.5 μm) or idler wavelengths (3 μm).

Xiaoling Zhang, Yong Geng

The 6G era necessitates advanced multiplexing techniques that fully utilize various physical dimensions, including time, frequency, polarization, and space to enhance the achievable bitrate per wavelength and satisfy growing demands for capacity and spectral efficiency. Power domain hybrid modulation (PDHM) emerges as a viable technology to overcome the orthogonal limitations inherent in existing multiplexing schemes. In this paper, we introduce an iterative successive interference cancelation (SIC) algorithm for coherent optical transmission systems employing PDHM. The proposed system multiplexes a 16-ary quadrature amplitude modulation (16-QAM) signal with a quadrature phase shift keying (QPSK) signal at distinct power ratios. With the proposed iterative SIC, the system performance is improved by about one order of magnitude.

Jikai Wang, Sven Burckhard, Sonam Smitha Ravi et al.

{We report on an intensity-only and deep-learning based method for laser beam characterization that allows to predict the underlying optical field within milliseconds. A simple near-field / far-field camera setup enables online control of an adaptive optics to optimize beam quality. The robustness and precision of the method is enhanced by applying the concept of phase diversity based on spiral phase plates.

C. L. Carilli, L. Torino, B. Nikolic et al.

Wave front sensing of the surface of equal phase for a propagating electromagnetic wave is a vital technology in fields ranging from real time adaptive optics, to high accuracy metrology, to medical optometry. We have developed a new method of wavefront sensing that makes a direct measurement of the electromagnetic phase distribution, or path-length delay, across an optical wavefront. The method is based on techniques developed in radio astronomical interferometric imaging. The method employs optical interferometry using a 2-D aperture mask, a Fourier transform of the interferogram to derive interferometric visibilities, and self-calibration of the complex visibilities to derive the voltage amplitude and phase gains at each hole in the mask, corresponding to corrections for non-uniform illumination and wavefront distortions across the aperture, respectively. The derived self-calibration gain phases are linearly proportional to the electromagnetic path-length distribution to each hole in the aperture mask, relative to the path-length to the reference hole, and hence represent a wavefront sensor with a precision of a small fraction of a wavelength. The method was tested at $λ=400\,$nm at the Xanadu optical bench at the ALBA synchrotron light source using a rotating mirror to insert tip-tilt changes in the wavefront. We reproduce the wavefront tilts to within $0.1''$ ($5\times 10^{-7}$~radians). We also derive the static metrology though the optical system for non-planar wavefront distortions to $\sim \pm1$~nm repeatability. Lastly, we derive frame-to-frame variations of the wavefront tilt due to vibrations of the optical components which range up to $\sim 0.5"$. These variations are relevant to adaptive optics applications. Based on the measured visibility phase noise after self-calibration, we estimate an rms path-length precision per 1~ms exposure of 0.6 nm.

LIU Zhaoyang, PAN Bitao

【Objective】Recent research efforts on Routing and Wavelength Assignment (RWA) for all optical networks are focused on Deep Reinforcement Learning (DRL) based algorithms. The DRL based RWA algorithms are mostly rely on the K Shortest Paths (KSP) routing to calculate candidate paths in advance, hence the DRL agent can choose possible actions from the precomputed paths. These KSP based models lack of flexibility and dynamicity, since they need to re-calculate the KSP for all the node pairs once the topology changes occur. To address this issue, this paper proposes an Adaptive and Efficient(ADE)-RWA algorithm based on DRL.【Methods】The key points and innovations of the ADE-RWA lie in that during the training process, the DRL agent takes actions in a step-by-step way instead of selecting from the precomputed K complete paths. Therefore, the routing strategies are dynamically adjustable in training even under the case of topology changes. It is because that the actions are open for the agent to take without concerning the limitations of the K fixed paths. Moreover, the ADE-RWA records the successfully assigned routes during the training in a LookUp Table (LUT). The algorithm turns to LUT checking for finding the available routes once the DRL training is converged, since at that time the LUT has acquired enough information for the RWA from the DRL training. The LUT based routing can effectively reduce the computational costs and improve the efficiency of RWA. In addition, the DRL training phase and LUT routing phase are real-time switchable. The algorithm turns to the DRL training phase when a link failure caused topology change occurs, and turns back to LUT checking when the model training is converged again.【Results】Experimental results show that compared with KSP-First Fit(FF)and Deep Reinforcement Learning Framework for Routing, Modulation and Spectrum Assignment (DeepRMSA), the blocking probability of ADE-RWA is reduced by 36% and 30% respectively. When a link failure occurs, the algorithm can quickly adapt to the changes in network topology.【Conclusion】The proposed DRL based RWA framework ADE-RWA can achieve adaptive routing and wavelength allocation under dynamic network conditions with low computational cost.

Chenxi Zhang, Jie Liu, Ying X. Gao et al.

Abstract As a member of organic porous crystal structure, metal organic frameworks (MOFs) material has more unique properties due to its large specific surface area, high porosity, diversified structure and functions, it has been successfully applied in new energy, microelectronics, chemical reaction medical science and other fields. However, no study about NiO-MOF for the ultrafast optics application has been reported till now. In this paper, NiO-MOF polyhedral particles is prepared by hydrothermal method and successfully applied to ultrafast photonics. The modulation depth of NiO-MOF is 18.98 % through a dual-balance detection system. Most importantly, the 109th harmonic solitons are realized for the first time based on NiO-MOF in a compact mode-locked fiber laser at 1.55 μm, the fiber laser has pulse duration of 766 fs and repetition frequency of 413 MHz. As far as we know, this is the first time NiO-MOF has been applied to realize harmonic mode-locking at the fs level of more than 400 MHz. Due to the rich variability of MOFs structure, this study successfully provides support for the application of MOFs material in advanced photonics.

Yang Zhao, Penglai Guo, Xiao-hui Li et al.

Abstract As a kind of novel allotrope of carbon, graphdiyne (GDY) has attracted wide interest of scientists from different fields. Due to excellent electrical and optical properties, it has important and promising prospects in the fields of energy, catalysis and optoelectronics, etc. However, investigations of this emerging material on nonlinear optics and ultrafast photonics are rarely involved. In our work, we have fabricated a saturable absorber (SA) based on graphdiyne and applied it to an erbium-doped fiber laser at the 1.5 μm region. Based on the evanescent field interaction, we obtain the mode-locked laser pulse at a center wavelength of 1564.70 nm which has a repetition rate of 12.05 MHz and a pulse width of 734 fs. This is the first time that graphdiyne has been used as a SA to obtain a mode-locked fiber laser in femtosecond level, which proves the great prospect of graphdiyne on fiber lasers and opens up a path for its application in ultrafast photonics and optoelectronics.

Yiwen Sun, Zhijie Mei, Xuejiao Xu et al.

Terahertz (THz) technology has seen significant advancements in the past decades, encompassing both fundamental scientific research, such as THz quantum optics, and highly applied areas like sixth-generation communications, medical imaging, and biosensing. However, the progress of on-chip THz integrated waveguides still lags behind that of THz sources and detectors. This is attributed to issues such as ohmic losses in microstrip lines, coplanar and hollow waveguides, bulky footprints, and reflection and scattering losses occurring at sharp bends or defects in conventional dielectric waveguides. Inspired by the quantum Hall effects and topological insulators in condensed matter systems, recent discoveries of topological phases of light have led to the development of topological waveguides. These waveguides exhibit remarkable phenomena, such as robust unidirectional propagation and reflectionless behavior against impurities or defects. As a result, they hold tremendous promise for THz on-chip applications. While THz photonic topological insulators (PTIs), including wave division, multiport couplers, and resonant cavities, have been demonstrated to cover a wavelength range of 800–2500 nm, research on tunable THz PTIs remains limited. In this perspective, we briefly reviewed a few examples of tunable PTIs, primarily concentrated in the infrared range. Furthermore, we proposed how these designs could benefit the development of THz on-chip PTIs. We explore the potential methods for achieving tunable THz PTIs through optical, electrical, and thermal means. Additionally, we present a design of THz PTIs for potential on-chip sensing applications. To support our speculation, several simulations were performed, providing valuable insights for future THz on-chip PTI designs.

D. Nazarova, L. Nedelchev, N. Berberova-Buhova et al.

Photoanisotropic materials, in particular azodyes and azopolymers, have attracted significant research interest in the last decades. This is due to their applications in polarization holography and 4G optics, enabling polarization-selective diffractive optical elements with unique properties, including circular polarization beam-splitters, polarization-selective bifocal lenses, and many others. Numerous methods have been applied to increase the photoinduced birefringence of these materials, and as a result, to obtain polarization holographic elements with a high diffraction efficiency. Recently, a new approach has emerged that has been extensively studied by many research groups, namely doping azobenzene-containing materials with nanoparticles with various compositions, sizes, and morphologies. The resulting nanocomposites have shown significant enhancement in their photoanisotropic response, including increased photoinduced birefringence, leading to a higher diffraction efficiency and a larger surface relief modulation in the case of polarization holographic recordings. This review aims to cover the most important achievements in this new but fast-growing field of research and to present an extensive comparative analysis of the result, reported by many research groups during the last two decades. Different hypotheses to explain the mechanism of photoanisotropy enhancement in these nanocomposites are also discussed. Finally, we present our vision for the future development of this scientific field and outline its potential applications in advanced photonics technologies.

C. De Angelis

Nonlinear science, i.e., the study of systems capable of generating new frequencies, is ubiquitous and fascinating; as opposed to linear science, where we often have well known tools to tackle a specific problem, when nonlinearity comes into play, and the whole can be more than the sum of its parts, we can seldom resort to standard techniques. Even in the non stochastic framework, the field is often unpredictable: the emergence of qualitatively new phenomena is anticipated and made welcome, offering incredible outcomes for basic and applied sciences. Nonlinear optics is a particular and rich subset of nonlinear science. Although nonlinear effects in optics are known since a very long time, modern nonlinear optics was born with the invention of the optical maser, today known as the laser. In a seminal paper by Franken and co-workers in 1961, second harmonic generation was demonstrated by tightly focusing a pulsed ruby optical maser into crystalline quartz (Franken et al., 1961). In the following years a plethora of nonlinear effects in lightmatter interaction were experimentally demonstrated and often rapidly found their way to market applications in several different fields, ranging from telecommunications to imaging for health care and characterization. Due to the short interaction lengths between light and matter, in the early stage, nonlinear optical effects were often associated with very low efficiencies; for this reason, a very important milestone has been set moving from bulk nonlinear optics to guided wave nonlinear optics. The flourishing field of nonlinear guided wave optics started shortly after the optical fiber became a popular transmission medium (Stolen et al., 1974). This gave an incredible boost to the efficiency of nonlinear optical effects, because light-matter interaction lengths could be increased by several orders of magnitude (from few centimeters to tens of kilometers). The richness of new physics, which since then has appeared, has deeply fed this research area and, in turn, the field has given back incredible success to the researchers. For all these reasons, nonlinear optics could quickly move into the field of extreme events; just to mention only a few of the remarkable outcomes of this part of the history of nonlinear optics: the field of solitons is strongly indebted to nonlinear optics and viceversa, since optical fibers gave an ideal playground where to observe and test the properties of these fascinating waves, which were first predicted in water waves and then became, in the sixties, one incredible chapter of modern mathematical physics (Zakharov and Shabat, 1970). This is, still today, a rich and flourishing research field with important, and sometimes surprising, outcomes for optical communications and optical sensing with new fascinating phenomena like rogue waves (Dudley, 2019). In line with what Richard Feynman said at the annual American Physical Society meeting in 1959, there is still plenty of room at the bottom, nonlinear optics, in the last 20 years, deeply dived into nanotechnologies and nanophotonics (Kauranen and Zayats, 2012; Shcherbakov et al., 2014; Carletti et al., 2015). Anelastic scattering from metallic and non metallic nanoparticles (Figure 1) is now a very hot research topic for both basic and applied Edited and reviewed by: Vincenzo Giannini, Instituto de Estructura de la Materia (IEM), Spain

Romil Audhkhasi, Johannes E. Fröch, A. Zhan et al.

Rapid advancements in autonomous systems and the Internet of Things have necessitated the development of compact and low-power image sensors to bridge the gap between the digital and physical world. To that end, sub-wavelength diffractive optics, commonly known as meta-optics, have garnered significant interest from the optics and photonics community due to their ability to achieve multiple functionalities within a small form factor. Despite years of research, however, the performance of meta-optics has often remained inferior compared to that of traditional refractive optics. In parallel, computational imaging techniques have emerged as a promising path to miniaturize optical systems, albeit often at the expense of higher power and latency. The lack of desired performance from either meta-optical or computational solutions has motivated researchers to look into a jointly optimized meta-optical–digital solution. While the meta-optical front end can preprocess the scene to reduce the computational load on the digital back end, the computational back end can in turn relax requirements on the meta-optics. In this Perspective, we provide an overview of this up-and-coming field, termed here as “software-defined meta-optics.” We highlight recent contributions that have advanced the current state of the art and point out directions toward which future research efforts should be directed to leverage the full potential of subwavelength photonic platforms in imaging and sensing applications. Synergistic technology transfer and commercialization of meta-optic technologies will pave the way for highly efficient, compact, and low-power imaging systems of the future.

Jiaye Wu, Xie Zetao, Yanhua Sha et al.

With its unique and exclusive linear and nonlinear optical characteristics, epsilon-near-zero (ENZ) photonics has drawn a tremendous amount of attention in the recent decade in the fields of nanophotonics, nonlinear optics, plasmonics, light-matter interactions, material science, applied optical science, etc. The extraordinary optical properties, relatively high tuning flexibility, and CMOS compatibility of ENZ materials make them popular and competitive candidates for nanophotonic devices and on-chip integration in all-optical and electro-optical platforms. With exclusive features and high performance, ENZ photonics can play a big role in optical communications and optical data processing. In this review, we give a focused discussion on recent advances of the theoretical and experimental studies on ENZ photonics, especially in the regime of nonlinear ENZ nanophotonics and its applications. First, we overview the basics of the ENZ concepts, mechanisms, and nonlinear ENZ nanophotonics. Then the new advancements in theoretical and experimental optical physics are reviewed. For nanophotonic applications, the recent decades saw rapid developments in various kinds of different ENZ-based devices and systems, which are discussed and analyzed in detail. Finally, we give our perspectives on where future endeavors can be made. © 2021 Chinese Laser Press

Zunyu Liu, Chaoyu Zhao, Shuangfeng Jia et al.

Abstract Multi-dimensional heterojunction materials have attracted much attention due to their intriguing properties, such as high efficiency, wide band gap regulation, low dimensional limitation, versatility and scalability. To further improve the performance of materials, researchers have combined materials with various dimensions using a wide variety of techniques. However, research on growth mechanism of such composite materials is still lacking. In this paper, the growth mechanism of multi-dimensional heterojunction composite material is studied using quasi-two-dimensional (quasi-2D) antimonene and quasi-one-dimensional (quasi-1D) antimony sulfide as examples. These are synthesized by a simple thermal injection method. It is observed that the consequent nanorods are oriented along six-fold symmetric directions on the nanoplate, forming ordered quasi-1D/quasi-2D heterostructures. Comprehensive transmission electron microscopy (TEM) characterizations confirm the chemical information and reveal orientational relationship between Sb2S3 nanorods and the Sb nanoplate as substrate. Further density functional theory calculations indicate that interfacial binding energy is the primary deciding factor for the self-assembly of ordered structures. These details may fill the gaps in the research on multi-dimensional composite materials with ordered structures, and promote their future versatile applications. Graphical Abstract

A. Tamulevičienė, T. Tamulevičius, S. Tamulevičius

Lithuania is recognized as a laser-tech cluster and therefore the Materials Engineering and Nanotechnologies study program carried out at the Kaunas University of Technology is tempting to address the competencies required by the beneficiaries. Students are introduced to Optics and Laser technologies via three recently revised dedicated courses that have theory lectures, practical tasks, and laboratory works. The endeavor starts at the basic level like geometrical optics, light interference, diffraction, etc. going through modern optics covering optical devices and processes, and finalizes with a deeper understanding of topics covering nonlinear and ultrafast laser optics, plasmonics, and laser material processing. The study program is unique in a way that it provides double degree diplomas both in Physics and Materials Engineering fields. Considering the challenges and needs of the laser-related industry in Lithuania the courses in Optics were adapted to include fundamental and applied research-based topics along with problem-based learning tasks directly related to the real-life problems that expand the content of the classical textbooks. Lab work tasks are performed at university research laboratories employing the state-of-the-art femtosecond laser, laser micromachining workstation, and transient absorption spectrometer allowing students to get familiar with the locally produced photonics products. Handson experiences with contemporary technologies together with a critical amount of fundamental knowledge in photonics later on stimulate students seeking a job position in the laser/optics-related industry in Lithuania. The feedback from the students shows that the problem-based learning approach and teamwork allow students to get a better understanding and more in-depth knowledge of the field and teaches soft skills expected by employers.

G. Lin, A. Coillet, Y. Chembo

Anupamaa Rampur, D. Spangenberg, B. Sierro et al.

A new generation of ultrafast and low-noise supercontinuum (SC) sources is currently emerging, driven by the con-stantly increasing demands of spectroscopy, advanced microscopy, and ultrafast photonics applications for highly stable broadband coherent light sources. In this perspective, we review recent progress enabled by advances in nonlinear optical fiber design, detail our view on the largely untapped potential for noise control in nonlinear fiber optics, and present the noise fingerprinting technique for measuring and visualizing the noise of SC sources with unprecedented detail. In our outlook we highlight how these SC sources push the boundaries for many spectroscopy and imaging modalities, and focus on their role in the development of ultrafast fiber lasers and frequency combs with ultra-low amplitude and phase noise operating in the 2 µ m spectral region and beyond in the mid-IR.

Gengxin Chen, Kaixuan Chen, Ranfeng Gan et al.

Thin-film lithium niobate (TFLN) based traveling-wave modulators maintain simultaneously excellent performances, including large modulation bandwidth, high extinction ratio, low optical loss, and high modulation efficiency. Nevertheless, there still exists a balance between the driving voltage and modulation bandwidth. Here, we demonstrate an ultra-large bandwidth electro-optic modulator without compromising the driving voltage based on the TFLN platform on a silicon substrate, using a periodic capacitively loaded traveling-wave electrode. In order to compensate the slow-wave effect, an undercut etching technique for the silicon substrate is introduced to decrease the microwave refractive index. Our demonstrated devices represent both low optical and low microwave losses, which leads to a negligible optical insertion loss of 0.2 dB and a large electro-optic bandwidth with a roll-off of 1.4 dB at 67 GHz for a 10 mm-long device. A low half-wave voltage of 2.2 V is also achieved. Data rates up to 112 Gb s−1 with PAM-4 modulation are demonstrated. The compatibility of the proposed modulator to silicon photonics facilitates its integration with matured silicon photonic components using, e.g., hybrid integration technologies.

Ł. Wilk, Ł. Wilk, D. Mielczarek et al.

The use of deep machine learning methods for semantic classification of city mesh models is one of the current trends in geoscience development. Thanks to the thriving development of Convolutional Neural Networks (CNNs) it is now achievable to conduct fully automated process of building aforementioned 3D model by means of photogrammetric techniques and supplement it with additional semantic information obtained by Artificial Intelligence (AI) algorithms. In order to guarantee the comprehensiveness of said information it is essential to use an extensive range of 3D data including oblique aerial imagery and aerial laser scanning (ALS). Such comprehensive 3D mesh models may be later implemented in many Digital Twin class solutions additionally supported with modern GIS systems and its algorithms. To proof the validity of this thesis, the article showcases results of research conducted using deep learning based solutions tested on two datasets - real-world data in the form of oblique aerial images and ALS point clouds acquired in Bordeaux, France using novel Leica CityMapper-1 multisensoral system and large-scale dataset from SUM: A Benchmark Dataset of Semantic Urban Meshes. Both subalgorithms make use of CNNs as its core-feature. To perform accurate classification of oblique aerial scenes PSP-Net architecture accelerated by techniques of transfer learning has been used. Second algorithm destined for ALS point clouds utilizes CNN as well, but in this case implementation is based on proprietary architecture. The results of the experiments demonstrate that the utilizing these two mutually complementary solutions to extract new semantic information for city mesh models in proposed manner compared with the state-of-the-art methods achieves competitive classification performance.