Recently, it was demonstrated that a new type of radio frequency surface electromagnetic wave appears on the surface of a lossy conductive medium in the presence of dielectric permittivity gradients. We present theoretical and experimental study of gradient surface electromagnetic wave (GSEW) excitation and propagation on such conductive surfaces as various metals, water, and human skin. The geometry of our experiments is designed to emulate various potential biosensing and bioimaging applications of GSEW. We demonstrate the capability of GSEW-based techniques to detect the presence of metallic and dielectric objects underwater in close proximity to the water surface. Since the dielectric properties of the human body are similar to those of water, we anticipate that the developed GSEW technique may supplement X-ray and ultrasound-based biosensing and bioimaging.

Electromagnetic properties of water and water interfaces in the radio frequency range have fundamental importance in such diverse fields of science and technology as physics, chemistry, life sciences and wireless communications. Despite their importance, many aspects of these properties remain controversial or unresolved, especially where it concerns water response to radio frequency electromagnetic fields inside biological matter or near biological interfaces. Here we note that in the radio frequency range water belongs to a class of electromagnetic materials in which the real part of their complex dielectric permittivity-squared approximately equals zero. We demonstrate that surface electromagnetic waves in such materials may exhibit a “plasmonic gradient resonance”, which leads to highly unusual propagation properties of radio fields. Based on our computations, the plasmonic gradient resonance in water may be observed in the frequency range from 2 MHz to 20 GHz, depending on the interface properties and water salinity. Our detailed radio communication experiments underwater indeed reveal such a resonant field behavior at the frequency of 50 MHz at 0.25 S/m water conductivity. The anomalous propagation properties of surface electromagnetic waves at resonance result in extremely large penetration distances and depths of radio fields underwater, reaching hundreds and in some cases thousands of skin depths. Similar resonances should be observable in a very broad range of materials and electromagnetic frequencies, from radio communication underground and underwater, to super-resolution radio frequency biosensing and bioimaging, and silicon ultraviolet nanophotonics.

While electromagnetic metamaterials completely revolutionized optics and radio frequency engineering, recent progress in the development of conceptually related electronic metamaterials was more slow. Similar to electromagnetic metamaterials, which engineer material response to the electromagnetic field of a photon, the purpose of electronic metamaterials is to affect electron propagation and its wave function by changing material response to its electric field. This makes electronic metamaterials an ideal tool for engineering light–matter interaction in semiconductors and superconductors. Here, we propose the use of Fermi’s quantum refraction, which was previously observed in the terahertz spectroscopy of Rydberg atoms and two-dimensional surface electronic states, as a novel tool in quantum electronic metamaterial design. In particular, we demonstrate several potential applications of this concept in two-dimensional metamaterial superconductors and “universal quantum dots” designed for operation in the terahertz frequency range.

Geometry- and gravity-induced effective photon mass is known to arise in many cases, such as various optical waveguides, Kaluza-Klein theories, and many other optical and general relativity situations. Here we study the appearance of effective photon mass in the Newtonian limit due to the presence of a gravity gradient emulated by an electromagnetic medium. The effective photon mass squared appears to be proportional to the local gravity gradient, and it becomes negative in an optical anti-waveguide around the unstable equilibrium location. A similar effect is observed in the emulated Kottler-M & oslash;ller spacetime where the absolute value of the gravity-induced effective photon mass appears to coincide with the Unruh temperature. We demonstrate that similar to the Unruh effect, a bath of thermal radiation should be observed in an optical anti-waveguide near the unstable equilibrium, whose temperature is defined by the emulated local gravity gradient, and which remains unchanged in the c -> infinity limit.

Recent theoretical and experimental work demonstrated that nonlinear optics of ferrofluid-based hyperbolic metamaterials exhibits very unusual 2+2-dimensional spatiotemporal dynamics. Here we report a detailed microscopic study of mutual interactions of individual self-focused optical filaments inside this metamaterial. In agreement with theoretical expectations, the observed mutual interactions of individual filaments exhibit strong similarities with general relativity in 2+1 dimensions. This observation is very important since 2+1-dimensional gravity is an exactly solvable theory even in the quantum gravity limit.

Recent theoretical and experimental work demonstrated that nonlinear optics of ferrofluid-based hyperbolic metamaterials exhibit very unusual spatiotemporal dynamics. Here a detailed theoretical and experimental study of mutual interactions of individual self-focused optical filaments inside this metamaterial is reported. In agreement with theoretical expectations, the observed mutual interactions of individual filaments exhibit strong similarities with general relativity in 2+1 dimensions, which predicts that these interactions must have predominantly non-Newtonian topological character. This observation is important since 2+1-dimensional gravity is an exactly solvable theory even in the quantum gravity limit.

A portable radio communication system operating in the 30 MHz band and capable of transmitting high-definition live underwater video images is presented. The system operation is based on launching electromagnetic surface waves propagating along water-air interface using specially designed surface wave antennas. Since the propagation length of the surface electromagnetic waves far exceeds the skin depth of bulk radio waves at the same frequency, this technique is useful for video communication underwater over distances of several meters. Also, this system appears to be efficient at communicating through the water-air interface.

Geometry and gravity induced effective photon mass is known to arise in many cases, such as various optical waveguides, Kaluza-Klein theories, and many other optical and general relativity situations. Here we study the appearance of effective photon mass in the Newtonian limit due to the presence of gravity gradient in a locally inertial reference frame. The effective photon mass squared appears to be proportional to the local gravity gradient, and it becomes tachyonic around unstable equilibrium locations. A similar effect is observed in the Kottler-Moller spacetime where the absolute value of the gravity-induced effective photon mass appears to coincide with the Unruh temperature. We demonstrate that similar to Unruh effect, a bath of thermal radiation is observed near the unstable equilibrium, which temperature is defined by the local gravity gradient, and which remains unchanged in the limit of infinite light velocity.

We demonstrate that a gradual interface between gold and silver supports the propagation of a novel kind of surface electromagnetic wave, which is different from the more well-known surface plasmon polaritons. The existence of such surface waves leads to a paradoxical situation in which a continuous metal barrier which does not have any pinholes may exhibit considerably increased light transmission if the barrier is made of two different metals. A spectroscopic study of this effect is reported.

The mid-T-C superconductor Ba1-XKXBiO3 (BKBO) exhibits different superconducting mechanisms depending on x, in the range similar to 0.35-0.65. The optimal doping for the highest T-C is reported to be around x = 0.4. To understand more about the dependence of the superconducting mechanism on x, high quality and reproducible epitaxial films with controlled x are needed. This has been challenging owing to the volatility of K and (to a lesser extent) Bi. In this work, we use pulsed laser deposition (PLD) with several novel process steps to achieve high-quality films in a reproducible way. These include a modified method for target preparation, a low NO2 growth pressure, and precise positioning of substrates in the PLD plume. Optimum T-C films (32 K onset) were grown from an x = 0.4 target, i.e. with no excess K, as is normally used. Stable, higher K content films (made from an x = 0.45 target), were also grown. These x = 0.45 films had a lower T-C (22.5 K onset), as expected for (K) overdoped films, with very high upper critical field, H-C2 (0 K), and irreversibility field, H-irr (0 K), values, from linear extrapolation, of similar to 31.7 T and similar to 28.8 T, respectively. The growth methodology demonstrated in this work is highly beneficial for fundamental mechanistic studies of this complex superconductor on which there is renewed interest, and where controlled compositions and crystalline quality are currently limited.

Label-free super-resolution (LFSR) imaging relies on light-scattering processes in nanoscale objects without a need for fluorescent (FL) staining required in super-resolved FL microscopy. The objectives of this Roadmap are to present a comprehensive vision of the developments, the state-of-the-art in this field, and to discuss the resolution boundaries and hurdles which need to be overcome to break the classical diffraction limit of the LFSR imaging. The scope of this Roadmap spans from the advanced interference detection techniques, where the diffraction-limited lateral resolution is combined with unsurpassed axial and temporal resolution, to techniques with true lateral super-resolution capability which are based on understanding resolution as an information science problem, on using novel structured illumination, near-field scanning, and nonlinear optics approaches, and on designing superlenses based on nanoplasmonics, metamaterials, transformation optics, and microsphere-assisted approaches. To this end, this Roadmap brings under the same umbrella researchers from the physics and biomedical optics communities in which such studies have often been developing separately. The ultimate intent of this paper is to create a vision for the current and future developments of LFSR imaging based on its physical mechanisms and to create a great opening for the series of articles in this field.

Underwater radio communication using surface electromagnetic waves propagating along the seawater-air and seawater-sea floor interfaces may provide a promising alternative to commonly used acoustic communication underwater.Here we present a detailed analytical and numerical consideration of TE and TM polarized surface electromagnetic wave properties.The resulting surface waves have propagation constants that permit communication ranges far longer than those of bulk propagation in the lossy media.We demonstrate theoretically and experimentally their ability to carry broadband radio signals over practical communication distances underwater.A 50 MHz radio signal was successfully carried along the sandy seabed over 7 m distance.

Wireless radio communications provide a backbone to our technological civilization. However, radio communications are widely believed to be impossible in many situations where radios are surrounded by conductive media, such as underwater or underground, thus making ocean exploration difficult and creating well-known mine safety problems. In addition, since most imaging techniques rely on electromagnetic waves, the difficulty of electromagnetic wave propagation through biological tissues, which are mostly made of water, also severely limits bioimaging. Here we show that contrary to common beliefs, radio signals may be efficiently propagated through water over useful distances. Both radio communication and radio imaging through water may be enabled by superlensing of surface electromagnetic waves propagating along the water surface. We have demonstrated underwater radio communication over distances of several hundred skin depth in the MHz frequency range, which would require sensitivity below 10 −100 W in a conventional radio communication channel. We also demonstrated subwavelength super-resolution radio imaging in the GHz range by using water surface as a superlens. Our results indicate new ways to perform bioimaging, as well as marine life safe techniques of wireless radio communication and imaging underwater, which are essential for ocean and seafloor exploration. We also anticipate that the developed techniques will provide invaluable means of studying the extraterrestrial water worlds, such as potentially inhabitable Jovian moons.

A theory of surface electromagnetic waves in gradient media exhibiting arbitrary surface gradients of dielectric permittivity and magnetic permeability has been developed. Novel low-loss propagating surface wave solutions have been found in the gradient media in which both dielectric permittivity and magnetic permeability are dominated by their imaginary parts. Several examples of gradient geometries in which the surface wave problem may be solved analytically have been found. Examples of practically useful surface wave geometries spanning from radio communication underwater to UV nanophotonics have been demonstrated.

Laser & Photonics ReviewsVolume 17, Issue 12 2370055 Front CoverFree Access Roadmap on Label-Free Super-Resolution Imaging (Laser Photonics Rev. 17(12)/2023) Vasily N. Astratov, Vasily N. AstratovSearch for more papers by this authorYair Ben Sahel, Yair Ben SahelSearch for more papers by this authorYonina C. Eldar, Yonina C. EldarSearch for more papers by this authorLuzhe Huang, Luzhe HuangSearch for more papers by this authorAydogan Ozcan, Aydogan OzcanSearch for more papers by this authorNikolay Zheludev, Nikolay ZheludevSearch for more papers by this authorJunxiang Zhao, Junxiang ZhaoSearch for more papers by this authorZachary Burns, Zachary BurnsSearch for more papers by this authorZhaowei Liu, Zhaowei LiuSearch for more papers by this authorEvgenii Narimanov, Evgenii NarimanovSearch for more papers by this authorNeha Goswami, Neha GoswamiSearch for more papers by this authorGabriel Popescu, Gabriel PopescuSearch for more papers by this authorEmanuel Pfitzner, Emanuel PfitznerSearch for more papers by this authorPhilipp Kukura, Philipp KukuraSearch for more papers by this authorYi-Teng Hsiao, Yi-Teng HsiaoSearch for more papers by this authorChia-Lung Hsieh, Chia-Lung HsiehSearch for more papers by this authorBrian Abbey, Brian AbbeySearch for more papers by this authorAlberto Diaspro, Alberto DiasproSearch for more papers by this authorAymeric LeGratiet, Aymeric LeGratietSearch for more papers by this authorPaolo Bianchini, Paolo BianchiniSearch for more papers by this authorNatan T. Shaked, Natan T. ShakedSearch for more papers by this authorBertrand Simon, Bertrand SimonSearch for more papers by this authorNicolas Verrier, Nicolas VerrierSearch for more papers by this authorMatthieu Debailleul, Matthieu DebailleulSearch for more papers by this authorOlivier Haeberlé, Olivier HaeberléSearch for more papers by this authorSheng Wang, Sheng WangSearch for more papers by this authorMengkun Liu, Mengkun LiuSearch for more papers by this authorYeran Bai, Yeran BaiSearch for more papers by this authorJi-Xin Cheng, Ji-Xin ChengSearch for more papers by this authorBehjat S. Kariman, Behjat S. KarimanSearch for more papers by this authorKatsumasa Fujita, Katsumasa FujitaSearch for more papers by this authorMoshe Sinvani, Moshe SinvaniSearch for more papers by this authorZeev Zalevsky, Zeev ZalevskySearch for more papers by this authorXiangping Li, Xiangping LiSearch for more papers by this authorGuan-Jie Huang, Guan-Jie HuangSearch for more papers by this authorShi-Wei Chu, Shi-Wei ChuSearch for more papers by this authorOmer Tzang, Omer TzangSearch for more papers by this authorDror Hershkovitz, Dror HershkovitzSearch for more papers by this authorOri Cheshnovsky, Ori CheshnovskySearch for more papers by this authorMikko J. Huttunen, Mikko J. HuttunenSearch for more papers by this authorStefan G. Stanciu, Stefan G. StanciuSearch for more papers by this authorVera N. Smolyaninova, Vera N. SmolyaninovaSearch for more papers by this authorIgor I. Smolyaninov, Igor I. SmolyaninovSearch for more papers by this authorUlf Leonhardt, Ulf LeonhardtSearch for more papers by this authorSahar Sahebdivan, Sahar SahebdivanSearch for more papers by this authorZengbo Wang, Zengbo WangSearch for more papers by this authorBoris Luk'yanchuk, Boris Luk'yanchukSearch for more papers by this authorLimin Wu, Limin WuSearch for more papers by this authorAlexey V. Maslov, Alexey V. MaslovSearch for more papers by this authorBoya Jin, Boya JinSearch for more papers by this authorConstantin R. Simovski, Constantin R. SimovskiSearch for more papers by this authorStephane Perrin, Stephane PerrinSearch for more papers by this authorPaul Montgomery, Paul MontgomerySearch for more papers by this authorSylvain Lecler, Sylvain LeclerSearch for more papers by this author Vasily N. Astratov, Vasily N. AstratovSearch for more papers by this authorYair Ben Sahel, Yair Ben SahelSearch for more papers by this authorYonina C. Eldar, Yonina C. EldarSearch for more papers by this authorLuzhe Huang, Luzhe HuangSearch for more papers by this authorAydogan Ozcan, Aydogan OzcanSearch for more papers by this authorNikolay Zheludev, Nikolay ZheludevSearch for more papers by this authorJunxiang Zhao, Junxiang ZhaoSearch for more papers by this authorZachary Burns, Zachary BurnsSearch for more papers by this authorZhaowei Liu, Zhaowei LiuSearch for more papers by this authorEvgenii Narimanov, Evgenii NarimanovSearch for more papers by this authorNeha Goswami, Neha GoswamiSearch for more papers by this authorGabriel Popescu, Gabriel PopescuSearch for more papers by this authorEmanuel Pfitzner, Emanuel PfitznerSearch for more papers by this authorPhilipp Kukura, Philipp KukuraSearch for more papers by this authorYi-Teng Hsiao, Yi-Teng HsiaoSearch for more papers by this authorChia-Lung Hsieh, Chia-Lung HsiehSearch for more papers by this authorBrian Abbey, Brian AbbeySearch for more papers by this authorAlberto Diaspro, Alberto DiasproSearch for more papers by this authorAymeric LeGratiet, Aymeric LeGratietSearch for more papers by this authorPaolo Bianchini, Paolo BianchiniSearch for more papers by this authorNatan T. Shaked, Natan T. ShakedSearch for more papers by this authorBertrand Simon, Bertrand SimonSearch for more papers by this authorNicolas Verrier, Nicolas VerrierSearch for more papers by this authorMatthieu Debailleul, Matthieu DebailleulSearch for more papers by this authorOlivier Haeberlé, Olivier HaeberléSearch for more papers by this authorSheng Wang, Sheng WangSearch for more papers by this authorMengkun Liu, Mengkun LiuSearch for more papers by this authorYeran Bai, Yeran BaiSearch for more papers by this authorJi-Xin Cheng, Ji-Xin ChengSearch for more papers by this authorBehjat S. Kariman, Behjat S. KarimanSearch for more papers by this authorKatsumasa Fujita, Katsumasa FujitaSearch for more papers by this authorMoshe Sinvani, Moshe SinvaniSearch for more papers by this authorZeev Zalevsky, Zeev ZalevskySearch for more papers by this authorXiangping Li, Xiangping LiSearch for more papers by this authorGuan-Jie Huang, Guan-Jie HuangSearch for more papers by this authorShi-Wei Chu, Shi-Wei ChuSearch for more papers by this authorOmer Tzang, Omer TzangSearch for more papers by this authorDror Hershkovitz, Dror HershkovitzSearch for more papers by this authorOri Cheshnovsky, Ori CheshnovskySearch for more papers by this authorMikko J. Huttunen, Mikko J. HuttunenSearch for more papers by this authorStefan G. Stanciu, Stefan G. StanciuSearch for more papers by this authorVera N. Smolyaninova, Vera N. SmolyaninovaSearch for more papers by this authorIgor I. Smolyaninov, Igor I. SmolyaninovSearch for more papers by this authorUlf Leonhardt, Ulf LeonhardtSearch for more papers by this authorSahar Sahebdivan, Sahar SahebdivanSearch for more papers by this authorZengbo Wang, Zengbo WangSearch for more papers by this authorBoris Luk'yanchuk, Boris Luk'yanchukSearch for more papers by this authorLimin Wu, Limin WuSearch for more papers by this authorAlexey V. Maslov, Alexey V. MaslovSearch for more papers by this authorBoya Jin, Boya JinSearch for more papers by this authorConstantin R. Simovski, Constantin R. SimovskiSearch for more papers by this authorStephane Perrin, Stephane PerrinSearch for more papers by this authorPaul Montgomery, Paul MontgomerySearch for more papers by this authorSylvain Lecler, Sylvain LeclerSearch for more papers by this author First published: 11 December 2023 https://doi.org/10.1002/lpor.202370055AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Graphical Abstract Roadmap on Label-Free Super-Resolution Imaging In article number 2200029, Vasily Astratov and colleagues representing 27 research teams worldwide created a roadmap on label-free super-resolution imaging. Its scope spans from diffraction-limited interference detection techniques to methods allowing to overcome classical diffraction limit without using fluorescent markers, which are based on information science; structured illumination; near-field, nonlinear, and transformation optics; and advanced superlens designs. Cover images are provided by Aydogan Ozcan and Nikolay Zheludev participating in this Roadmap. Volume17, Issue12December 20232370055 RelatedInformation

We study one of the interesting properties of the electromagnetic wave propagation in the Schwarzschild background spacetime in the framework of general relativity (GR). The electromagnetic wave equation has been derived from vacuum general relativistic Maxwell's equations. It is shown that the solutions for the electromagnetic field can be expanded in the spherical harmonic functions and all components of the electromagnetic fields can be expressed in terms of two radial profile functions. These radial profile functions can be expressed in terms of the confluent Heun function. The calculated behavior of the electric and magnetic susceptibilities near the event horizon appears to be similar to the susceptibilities of multiferroic materials near phase transition. The Curie temperature of this phase transition appears to coincide with the Hawking temperature.

We demonstrate that gradual interfaces between lossy conductive media support propagation of a novel kind of surface electromagnetic wave, which is different from the more well-known surface plasmon polaritons. Potential applications of these novel surface waves to monitor water surface and the seawater-ice interface, as well as other environmental sensing applications in the RF and optical domain are discussed.

Localization phenomena in light, scattering from random fluctuations of matter fields and space–time metrics near a black hole horizon, were predicted to produce a pronounced peak in the angular distribution of second-harmonic light in the direction normal to the horizon. Therefore, the detection of second-harmonic generation may become a viable observational tool to study spacetime physics near event horizons of astronomical black holes. The light localization phenomena near the horizon may be facilitated by the existence of surface electromagnetic wave solutions. In this communication, we study such surface electromagnetic wave solutions near the horizon of a Schwarzschild metric, describing a black hole in vacuum. We demonstrate that such surface wave solutions must appear when quantum gravity effects are taken into account. Potential observational evidence of this effect is also discussed.

|It is commonly believed that electromagnetic waves cannot propagate in lossy conductive media and that they quickly decay inside such media over short length scales of the order of the so-called skin depth. Here we prove that this common belief is incorrect if the conductive medium is strati(cid:12)ed. We demonstrate that electromagnetic waves in strati(cid:12)ed lossy conductive media may have propagating character and that the propagation length of such waves may be considerably larger than the skin depth in homogeneous media. Our (cid:12)ndings have broad implications in many (cid:12)elds of science and engineering. They enable radio communication and imaging in such strongly lossy conductive media as seawater, various soils, plasma, and biological tissues. They also enable novel electromagnetic metamaterial designs by mediating the effect of losses on electromagnetic signal propagation in metamaterials. Our results demonstrate a new class of inherently non-Hermitian electromagnetic media with high dissipation, no gain, and no PT-symmetry, which nevertheless have almost real eigenvalue spectrum. the interface with the conductive stratum (e). Propagation length of the TM mode along the \parabolic" stratum considerably exceeds the conventional skin depth in a homogeneous medium.