Open Access Published by De Gruyter

Volume 9 Issue 5 - Special Issue: New trends in nanophotonics; Guest Editors: Sunae So, Namkyoo Park, Hak Joo Lee, Junsuk Rho

Issue of Nanophotonics

Contents
Journal Overview

Editorial

Open Access March 25, 2020

New trends in nanophotonics

Sunae So, Namkyoo Park, Hak Joo Lee, Junsuk Rho

Page range: 983-985

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Reviews

Open Access February 3, 2020

Optical wavefront shaping based on functional metasurfaces

Qunshuo Wei, Lingling Huang, Thomas Zentgraf, Yongtian Wang

Page range: 987-1002

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Abstract

Regarded as a kind of smart surfaces, metasurfaces can arbitrarily tailor the amplitude, phase, and polarization of light. Metasurfaces usually consist of subwavelength nanoantenna or nanoresonator arrays, which are delicately designed and processed. As an ultrathin, miniaturized versatile wavefront modulation device, metasurfaces have great information capacity and can arouse the future development of highly integrated micronano optoelectronic systems. Exploiting the advantages of ultrasmall pixels, flexible design freedom, low loss, and easy processing properties, metasurfaces provide potential feasibility and new perspectives for a plethora of applications. Here we review the research progress of metasurfaces for holographic displays, polarization conversion, active modulation, linear and nonlinear wavefront modulation, and prospect the future development trend of metasurfaces.

Open Access February 17, 2020

Recent advances in optical metasurfaces for polarization detection and engineered polarization profiles

Yuttana Intaravanne, Xianzhong Chen

Page range: 1003-1014

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Abstract

Like amplitude, phase and frequency, polarization is one of the fundamental properties of light, which can be used to record, process and store information. Optical metasurfaces are ultrathin inhomogeneous media with planar nanostructures that can manipulate the optical properties of light at the subwavelength scale, which have become a current subject of intense research due to the desirable control of light propagation. The unprecedented capability of optical metasurfaces in the manipulation of the light’s polarization at subwavelength resolution has provided an unusual approach for polarization detection and arbitrary manipulation of polarization profiles. A compact metasurface platform has been demonstrated to detect polarization information of a light beam and to arbitrarily engineer a polarization profile that is very difficult or impossible to realize with conventional optical elements. This review will focus on the recent progress on ultrathin metasurface devices for polarization detection and realization of customized polarization profiles. Optical metasurfaces have provided new opportunities for polarization detection and manipulation, which can facilitate real-world deployment of polarization-related devices and systems in various research fields, including sensing, imaging, encryption, optical communications, quantum science, and fundamental physics.

Research Articles

Open Access February 6, 2020

Broadband wavelength demultiplexer using Fano-resonant metasurface

Sang-Eun Mun, Chulsoo Choi, Jongwoo Hong, Byoungho Lee

Page range: 1015-1022

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Abstract

Fano resonance, one of the interesting resonance phenomena in physics, provides versatile applications when combined with a concept of metasurface in nanophotonics. Fano-resonant metasurface (FRM) is attracting a lot of attention due to its superior narrowband characteristics as well as design freedom of metasurfaces in nanoscale. However, only the control of apparent asymmetric spectral nature of Fano resonance has been focused at applications such as optical sensors, as the amplitude feature of Fano resonances is relatively easy to control and can be measured by an experimental setup. Here, a method for modulating the phase information of FRM by both simulation and experiment is demonstrated. As a proof of concept, an optical demultiplexer, which can divide four target wavelengths in different directions of free space, is verified experimentally. It covers a broadband wavelength range of more than 350 nm in the near-infrared region with extremely small full-width at half-maximum. This approach can offer the complete control of FRM for a wide range of applications, including optical multiplexers, routers, filters, and switches, beyond conventional applications that have been limited to the amplitude control of Fano resonance.

Open Access June 2, 2020

Direction control of colloidal quantum dot emission using dielectric metasurfaces

Yeonsang Park, Hyochul Kim, Jeong-Yub Lee, Woong Ko, Kideock Bae, Kyung-Sang Cho

Page range: 1023-1030

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Abstract

Owing to the recent developments of dielectric metasurfaces, their applications have been expanding from those pertaining to the thickness shrinkage of passive optical elements, such as lenses, polarizers, and quarter-wave plates, to applications pertaining to their integration with active optical devices, such as vertical-cavity surface-emitting lasers. Even though directional lasing and beam shaping of laser emission have been successfully demonstrated, the integration of metasurfaces with random light sources, such as light-emitting diodes, is limited because of function and efficiency issues attributed to the fact that metasurfaces are basically based on the resonance property of the nanostructure. To control the direction of emission from colloidal quantum dots, we present a dielectric metasurface deflector composed of two asymmetric TiO 2 nanoposts. TiO 2 deflector arrays were fabricated with a dry etching method that is adaptive to mass production and integrated with a colloidal quantum dot resonant cavity formed by sandwiching two distributed Bragg reflectors. To ensure the deflection ability of the fabricated sample, we measured the photoluminescence and far-field patterns of emission from the resonant cavity. From the obtained results, we demonstrated that the colloidal quantum dot emission transmitted through our deflector arrays was deflected by 18°, and the efficiency of deflection was 71% with respect to the emission from the resonant cavity. This integration of dielectric metasurfaces with a resonant cavity shows the possibility of expanding the application of visible metasurfaces in active devices and may help to develop next-generation active devices with novel functions.

Open Access February 12, 2020

Observation of an exceptional point in a non-Hermitian metasurface

Sang Hyun Park, Sung-Gyu Lee, Soojeong Baek, Taewoo Ha, Sanghyub Lee, Bumki Min, Shuang Zhang, Mark Lawrence, Teun-Teun Kim

Page range: 1031-1039

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Abstract

Exceptional points (EPs), also known as non-Hermitian degeneracies, have been observed in parity-time symmetric metasurfaces as parity-time symmetry breaking points. However, the parity-time symmetry condition puts constraints on the metasurface parameter space, excluding the full examination of unique properties that stem from an EP. Here, we thus design a general non-Hermitian metasurface with a unit cell containing two orthogonally oriented split-ring resonators (SRRs) with overlapping resonance but different scattering rates and radiation efficiencies. Such a design grants us full access to the parameter space around the EP. The parameter space around the EP is first examined by varying the incident radiation frequency and coupling between SRRs. We further demonstrate that the EP is also observable by varying the incident radiation frequency along with the incident angle. Through both methods, we validate the existence of an EP by observing unique level crossing behavior, eigenstate swapping under encirclement, and asymmetric transmission of circularly polarized light.

Review

Open Access February 17, 2020

Deep learning enabled inverse design in nanophotonics

Sunae So, Trevon Badloe, Jaebum Noh, Jorge Bravo-Abad, Junsuk Rho

Page range: 1041-1057

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Abstract

Deep learning has become the dominant approach in artificial intelligence to solve complex data-driven problems. Originally applied almost exclusively in computer-science areas such as image analysis and nature language processing, deep learning has rapidly entered a wide variety of scientific fields including physics, chemistry and material science. Very recently, deep neural networks have been introduced in the field of nanophotonics as a powerful way of obtaining the nonlinear mapping between the topology and composition of arbitrary nanophotonic structures and their associated functional properties. In this paper, we have discussed the recent progress in the application of deep learning to the inverse design of nanophotonic devices, mainly focusing on the three existing learning paradigms of supervised-, unsupervised-, and reinforcement learning. Deep learning forward modelling i.e. how artificial intelligence learns how to solve Maxwell’s equations, is also discussed, along with an outlook of this rapidly evolving research area.

Research Articles

Open Access November 19, 2019

Simulator-based training of generative neural networks for the inverse design of metasurfaces

Jiaqi Jiang, Jonathan A. Fan

Page range: 1059-1069

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Abstract

Metasurfaces are subwavelength-structured artificial media that can shape and localize electromagnetic waves in unique ways. The inverse design of these devices is a non-convex optimization problem in a high dimensional space, making global optimization a major challenge. We present a new type of population-based global optimization algorithm for metasurfaces that is enabled by the training of a generative neural network. The loss function used for backpropagation depends on the generated pattern layouts, their efficiencies, and efficiency gradients, which are calculated by the adjoint variables method using forward and adjoint electromagnetic simulations. We observe that the distribution of devices generated by the network continuously shifts towards high performance design space regions over the course of optimization. Upon training completion, the best generated devices have efficiencies comparable to or exceeding the best devices designed using standard topology optimization. Our proposed global optimization algorithm can generally apply to other gradient-based optimization problems in optics, mechanics, and electronics.

Open Access February 22, 2020

Direct detection of charge and discharge process in supercapacitor by fiber-optic LSPR sensors

Siyu Qian, Xinlong Chen, Shiyu Jiang, Qiwen Pan, Yachen Gao, Lei Wang, Wei Peng, Shanjun Liang, Jie Zhu, Shengchun Liu

Page range: 1071-1079

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Abstract

Supercapacitors with high power density, ultralong lifespan and wide range operating temperature have drawn significant attention in recent years. However, monitoring the state of charge in supercapacitors in a cost-effective and flexible way is still challenging. Techniques such as transmission electron microscopy and X-ray diffraction can analyze the characteristics of supercapacitor well. But with large size and high price, they are not suitable for daily monitoring of the supercapacitors’ operation. In this paper, a low cost and easily fabricated fiber-optic localized surface plasmon resonance (LSPR) probe is proposed to monitor the state of charge of the electrode in a supercapacitor. The Au nanoparticles were loading on the fiber core as LSPR sensing region. In order to implant the fiber in the supercapacitor, a reflective type of fiber sensor was used. The results show that this tiny fiber-optic LSPR sensor can provide online monitoring of the state of charge during the charging and discharging process in situ . The intensity shift in LSPR sensor has a good linear relationship with the state of charge calculated by standard galvanostatic charging and discharging test. In addition, this LSPR sensor is insensitive to the temperature change, presenting a great potential in practical applications.

Open Access April 13, 2020

Differentiating and quantifying exosome secretion from a single cell using quasi-bound states in the continuum

Abdoulaye Ndao, Liyi Hsu, Wei Cai, Jeongho Ha, Junhee Park, Rushin Contractor, Yuhwa Lo, Boubacar Kanté

Page range: 1081-1086

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Abstract

One of the key challenges in biology is to understand how individual cells process information and respond to perturbations. However, most of the existing single-cell analysis methods can only provide a glimpse of cell properties at specific time points and are unable to provide cell secretion and protein analysis at single-cell resolution. To address the limits of existing methods and to accelerate discoveries from single-cell studies, we propose and experimentally demonstrate a new sensor based on bound states in the continuum to quantify exosome secretion from a single cell. Our optical sensors demonstrate high-sensitivity refractive index detection. Because of the strong overlap between the medium supporting the mode and the analytes, such an optical cavity has a figure of merit of 677 and sensitivity of 440 nm/RIU. Such results facilitate technological progress for highly conducive optical sensors for different biomedical applications.

Review

Open Access February 12, 2020

Dispersion engineering and measurement of whispering gallery mode microresonator for Kerr frequency comb generation

Shun Fujii, Takasumi Tanabe

Page range: 1087-1104

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Abstract

Designing and engineering microresonator dispersion are essential for generating microresonator frequency comb. Microresonator frequency combs (microcombs, Kerr frequency combs) offer the potential for various attractive applications as a new type of coherent light source that is power efficient and compact and has a high repetition rate and a broad bandwidth. They are easily driven with a continuous-wave pump laser with adequate frequency tuning; however, the resonators must have a high quality ( Q ) factor and suitable dispersion. The emergence of cavity enhanced four-wave mixing, which is based on third-order susceptibility in the host material, results in the generation of broadband and coherent optical frequency combs in the frequency domain equivalent to an optical pulse in the time domain. The platforms on which Kerr frequency combs can be observed have been developed, thanks to intensive efforts by many researchers over a few decades. Ultrahigh- Q whispering gallery mode (WGM) microresonators are one of the major platforms since they can be made of a wide range of material including silica glass, fluoride crystals and semiconductors. In this review, we focus on the dispersion engineering of WGM microresonators by designing the geometry of the resonators based on numerical simulation. In addition, we discuss experimental methods for measuring resonator dispersion. Finally, we describe experimental results for Kerr frequency combs where second- and higher-order dispersions influence their optical spectra.

Research Article

Open Access April 2, 2020

Plasmonic electro-optic modulator based on degenerate semiconductor interfaces

Raj K. Vinnakota, Zuoming Dong, Andrew F. Briggs, Seth R. Bank, Daniel Wasserman, Dentcho A. Genov

Page range: 1105-1113

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Abstract

We present a semiconductor-based optoelectronic switch based on active modulation of surface plasmon polaritons (SPPs) at lattice-matched indium gallium arsenide (In 0.53 Ga 0.47 As) degenerately doped pn ++ junctions. The experimental device, which we refer to as a surface plasmon polariton diode (SPPD), is characterized electrically and optically, showing far-field reflectivity modulation for mid-IR wavelengths. Self-consistent electro-optic multiphysics simulations of the device’s electrical and electromagnetic response have been performed to estimate bias-dependent modulation and switching times. The numerical model shows a strong agreement with the experimental results, validating the claim of excitation and modulation of SPPs at the junction, thus potentially providing a new pathway toward fast optoelectronic devices.

Reviews

Open Access March 19, 2020

Multipole and multimode engineering in Mie resonance-based metastructures

Tianji Liu, Rongyang Xu, Peng Yu, Zhiming Wang, Junichi Takahara

Page range: 1115-1137

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Abstract

Benefited from the well-known Mie resonance, a plethora of physical phenomena and applications are attracting attention in current research on dielectric-based nanophotonics. High-index dielectric metastructures are favorable to enhance light-matter interaction in nanoscale with advantages such as low loss, optical magnetism, and multipolar responses, which are superior to their plasmonic counterpart. In this review, we highlight the important role played by Mie resonance-based multipolar and multimodal interaction in nanophotonics, introducing the concept of “multipole and multimode engineering” in artificially engineered dielectric-based metastructures and providing an overview of the recent progress of this fast-developing area. The scope of multipole and multimode engineering is restricted not only in multipolar interferences of meta-atom and meta-molecule but also in the nontrivial intermodal coupling (Fano resonance and bound states in the continuum), in the collective mode and the surface lattice mode appearing via periodic meta-lattices and aperiodic meta-assembly, in chiral enhancement via chiral and achiral dielectric metastructures, and in Mie resonance-mediated hybrid structures (Mie-plasmon and Mie-exciton). Detailed examples and the underlying physics of this area are discussed in-depth, in order to lead the multifunctional metastructures for novel applications in the future.

Open Access February 4, 2020

3D and 4D printing for optics and metaphotonics

Hoon Yeub Jeong, Eunsongyi Lee, Soo-Chan An, Yeonsoo Lim, Young Chul Jun

Page range: 1139-1160

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Abstract

Three-dimensional (3D) printing is a new paradigm in customized manufacturing and allows the fabrication of complex optical components and metaphotonic structures that are difficult to realize via traditional methods. Conventional lithography techniques are usually limited to planar patterning, but 3D printing can allow the fabrication and integration of complex shapes or multiple parts along the out-of-plane direction. Additionally, 3D printing can allow printing on curved surfaces. Four-dimensional (4D) printing adds active, responsive functions to 3D-printed structures and provides new avenues for active, reconfigurable optical and microwave structures. This review introduces recent developments in 3D and 4D printing, with emphasis on topics that are interesting for the nanophotonics and metaphotonics communities. In this article, we have first discussed functional materials for 3D and 4D printing. Then, we have presented the various designs and applications of 3D and 4D printing in the optical, terahertz, and microwave domains. 3D printing can be ideal for customized, nonconventional optical components and complex metaphotonic structures. Furthermore, with various printable smart materials, 4D printing might provide a unique platform for active and reconfigurable structures. Therefore, 3D and 4D printing can introduce unprecedented opportunities in optics and metaphotonics and may have applications in freeform optics, integrated optical and optoelectronic devices, displays, optical sensors, antennas, active and tunable photonic devices, and biomedicine. Abundant new opportunities exist for exploration.

Open Access April 1, 2020

Photonic flat-band lattices and unconventional light localization

Liqin Tang, Daohong Song, Shiqi Xia, Shiqiang Xia, Jina Ma, Wenchao Yan, Yi Hu, Jingjun Xu, Daniel Leykam, Zhigang Chen

Page range: 1161-1176

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Abstract

Flat-band systems have attracted considerable interest in different branches of physics in the past decades, providing a flexible platform for studying fundamental phenomena associated with completely dispersionless bands within the whole Brillouin zone. Engineered flat-band structures have now been realized in a variety of systems, in particular, in the field of photonics. Flat-band localization, as an important phenomenon in solid-state physics, is fundamentally interesting in the exploration of exotic ground-state properties of many-body systems. However, direct observation of some flat-band phenomena is highly nontrivial in conventional condensed-matter systems because of intrinsic limitations. In this article, we briefly review recent developments on flat-band localization and the associated phenomena in various photonic lattices, including compact localized states, unconventional line states, and noncontractible loop states. We show that the photonic lattices offer a convenient platform for probing the underlying physics of flat-band systems, which may provide inspiration for exploring the fundamentals and applications of flat-band physics in other structured media from metamaterials to nanophotonic materials.

Research Article

Open Access February 4, 2020

From symmetric to asymmetric bowtie nanoantennas: electrostatic conformal mapping perspective

Victor Pacheco-Peña, Rúben A. Alves, Miguel Navarro-Cía

Page range: 1177-1187

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Abstract

Plasmonic nanoantennas have revolutionized the way we study and modulate light–matter interaction. Due to nanofabrication limitations, dimer-type nanoantennas always exhibit some degree of asymmetry, which is desirable in some cases. For instance, in sensing applications, asymmetry is sometimes induced by design in plasmonic nanoantennas to favor higher order nonradiative modes with sharp Fano line shapes. Regardless of the actual origin of the asymmetry, unintentional or intentional, an analytical frame that can deal with it in a seamless manner would be beneficial. We resort to conformal mapping for this task and we track the influence of the degree of asymmetry of the circular sectors composing gold bowtie nanoantennas on the nonradiative Purcell enhancement of a nearby nanoemitter. This manuscript reviews the contributions of conformal mapping to plasmonic nanoantennas and illustrates the advantages of the elegant analytical solution provided by conformal mapping to grasp physical insights, which can serve as a springboard for new plasmonic asymmetric nanoantenna designs.

Review

Open Access June 6, 2020

Tunable nanophotonics enabled by chalcogenide phase-change materials

Sajjad Abdollahramezani, Omid Hemmatyar, Hossein Taghinejad, Alex Krasnok, Yashar Kiarashinejad, Mohammadreza Zandehshahvar, Andrea Alù, Ali Adibi

Page range: 1189-1241

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Abstract

Nanophotonics has garnered intensive attention due to its unique capabilities in molding the flow of light in the subwavelength regime. Metasurfaces (MSs) and photonic integrated circuits (PICs) enable the realization of mass-producible, cost-effective, and efficient flat optical components for imaging, sensing, and communications. In order to enable nanophotonics with multipurpose functionalities, chalcogenide phase-change materials (PCMs) have been introduced as a promising platform for tunable and reconfigurable nanophotonic frameworks. Integration of non-volatile chalcogenide PCMs with unique properties such as drastic optical contrasts, fast switching speeds, and long-term stability grants substantial reconfiguration to the more conventional static nanophotonic platforms. In this review, we discuss state-of-the-art developments as well as emerging trends in tunable MSs and PICs using chalcogenide PCMs. We outline the unique material properties, structural transformation, and thermo-optic effects of well-established classes of chalcogenide PCMs. The emerging deep learning-based approaches for the optimization of reconfigurable MSs and the analysis of light-matter interactions are also discussed. The review is concluded by discussing existing challenges in the realization of adjustable nanophotonics and a perspective on the possible developments in this promising area.

About this journal

Nanophotonics covers recent international research results, specific developments in the field and novel applications and is published in partnership with Sciencewise. It belongs to the top journals in the field. Nanophotonics focuses on the interaction of photons with nano-structures, such as carbon nano-tubes, nano metal particles, nano crystals, semiconductor nano dots, photonic crystals, tissue and DNA. The journal covers the latest developments for physicists, engineers and material scientists, working in fields related to:

Plasmonics: metallic nanostructures and their optical properties
Meta materials, fundamentals and applications
Nanophotonic concepts and devices for solar energy harvesting and conversion
Near-field optical microscopy
Nanowaveguides and devices
Nano Lasers
Nanostructures, nanoparticles, nanotubes, nanowires, nanofibers
Photonic crystals
Integrated silicon photonics
Semiconductor quantum dots
Quantum optics & Quantum information
Ultrafast and nonlinear pulse propagation in nano materials and structures
Light-matter interaction, optical manipulation techniques
Nano-biophotonics
Optofluidics
Optomechanics
System applications based on nanophotonic devices
Nanofabrication techniques, thin film processing, self-assembly

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EARLY CAREER AWARD 2022

The Nanophotonics Early Career Award is an annual award presented to 4 early-career-stage scientists who have contributed significantly to advancements in the field of nanophotonics. The award winners will be awarded a prize of 1000 EUR and will have their Article Processing Charges waived for a period of two years. This award is fully sponsored by the Nanophotonics journal.

Nominations for the 2022 edition are now closed. Winners will be selected by the panel of Nanophotonics editors and will be announced soon.

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Publication Metrics

Average time from submission to initial Editorial Manager assessment: 5 days
Average time from submission to first decision
– Research articles: 22 days
– Review articles: 31 days
Average time from submission to final decision (all article types): 57 days
Average time from acceptance to publication: 13 days

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Special/Topical Issues

Published in 2022:

Photonic Angular Momentum (Guest Editors: Andrew Forbes, Qiwen Zhan and Siddharth Ramachandran)
New Trends in Nanophotonics and Advanced Photonic Materials (Guest Editor: Junsuk Rho)
Metamaterials and Plasmonics in Asia (Guest Editors: Lei Zhou, Tiejun Cui, JeongWeon Wu and Teruya Ishihara)
Tunable Nanophotonics (Guest Editors: Juejun Hu, Arseniy I. Kuznetsov, Volker J. Sorger, and Isabelle Staude)
Novel Two-Dimensional Materials Based Bio-Nanophotonic (Guest Editors: Hans Ågren, Jong Seung Kim and Han Zhang)

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Highly cited articles:

Polariton panorama
by D. N. Basov, Ana Asenjo-Garcia, P. James Schuck, Xiaoyang Zhu, Angel Rubio
Ultrasensitive terahertz sensing with high-Q toroidal dipole resonance governed by bound states in the continuum in all-dielectric metasurface
by Yulin Wang, Zhanghua Han, Yong Du, Jianyuan Qin
Non-Hermitian and topological photonics: optics at an exceptional point
by Midya Parto, Yuzhou G. N. Liu, Babak Bahari, Mercedeh Khajavikhan, Demetrios N. Christodoulides
Metasurfaces for biomedical applications: imaging and sensing from a nanophotonics perspective
by Shuyan Zhang, Chi Lok Wong, Shuwen Zeng, Renzhe Bi, Kolvyn Tai, Kishan Dholakia, Malini Olivo
THz spintronic emitters: a review on achievements and future challenges
by Evangelos Th. Papaioannou and René Beigang
Machine learning–assisted global optimization of photonic devices
by Zhaxylyk A. Kudyshev, Alexander V. Kildishev, Vladimir M. Shalaev, Alexandra Boltasseva
Topological photonics: Where do we go from here?
by Mordechai Segev, Miguel A. Bandres
Polymerization mechanisms initiated by spatio-temporally confined light
by Edvinas Skliutas, Migle Lebedevaite, Elmina Kabouraki, Tommaso Baldacchini, Jolita Ostrauskaite, Maria Vamvakaki, Maria Farsari, Saulius Juodkazis, Mangirdas Malinauskas
Highly ordered arrays of hat-shaped hierarchical nanostructures with different curvatures for sensitive SERS and plasmon-driven catalysis
by Chao Zhang, Zhaoxiang Li, Si Qiu, Weixi Lu, Mingrui Shao, Chang Ji, Guangcan Wang, Xiaofei Zhao, Jing Yu and Zhen Li
Manipulating the surface-enhanced Raman spectroscopy (SERS) activity and plasmon-driven catalytic efficiency by the control of Ag NP/graphene layers under optical excitation
by Xianwu Xiu, Liping Hou, Jing Yu, Shouzhen Jiang, Chonghui Li, Xiaofei Zhao, Qianqian Peng, Si Qiu, Chao Zhang, Baoyuan Man and Zhen Li