Mikhail Lapine

Bio: Mikhail Lapine is an academic researcher from University of Technology, Sydney. The author has contributed to research in topics: Metamaterial & Split-ring resonator. The author has an hindex of 26, co-authored 83 publications receiving 3773 citations. Previous affiliations of Mikhail Lapine include Centre for Ultrahigh Bandwidth Devices for Optical Systems & University of Seville.

Wide-band negative permeability of nonlinear metamaterials

Abstract: We propose a novel way to achieve an exceptionally wide frequency range where metamaterial possesses negative effective permeability. This can be achieved by employing a nonlinear response of metamaterials. We demonstrate that, with an appropriate design, a frequency band exceeding 100% is available for a range of signal amplitudes. Our proposal provides a significant improvement over the linear approach, opening a road towards broadband negative refraction and its applications.

Colloquium : Nonlinear metamaterials

Abstract: This Colloquium presents an overview of the research on nonlinear electromagnetic metamaterials The developed theoretical approaches and experimental designs are summarized, along with a systematic description of various phenomena available with nonlinear metamaterials

Active and tunable metamaterials

Abstract: Metamaterial research is an extremely important global activity that promises to change our lives in many different ways. These include making objects invisible and the dramatic impact of metamaterials upon the energy and medical sectors of society. Behind all of the applications, however, lies the business of creating metamaterials that are not going to be crippled by the kind of loss that is naturally heralded by use of resonant responses in their construction. This review sets out some solutions to the management of loss and gain, coupled to controlled and nonlinear behavior, and discusses some critical consequences concerning stability. Under the general heading of active and tunable metamaterials, an international spectrum of authors collaborates here to present a set of solutions that addresses these issues in several directions. As will be appreciated, the range of possible solutions is really fascinating, and it is hoped that these discussions will act as a further stimulus to the field.

Magnetoelastic metamaterials

Abstract: We propose and demonstrate experimentally a novel type of nonlinearity in metamaterials, which is induced by mechanical deformation of the structure. The nonlinearity arises from the introduction of an extra degree of freedom in the metamaterial, which allows for elastic displacement of the strongly interacting structural elements (see Fig. 1a). This type of nonlinearity relies on the counterplay between the electromagnetic attraction and the elastic repulsion, and the induced deformation alters the electromagnetic response of the entire structure, leading to the novel nonlinear response of the metamaterial.

Nonlinearity of a metamaterial arising from diode insertions into resonant conductive elements.

Abstract: We consider a possibility to create a metamaterial with nonlinear magnetic response in the microwave frequency range. Such a metamaterial is a regular periodic three-dimensional-array of resonant conductive elements with diodes as nonlinear insertions. We calculate the arising quadratic nonlinear susceptibility and show how it is controlled by the properties and arrangement of the structure elements as well as by the type and characteristics of the diode. We discuss the requirements for the diode necessary to optimize the nonlinear response of the proposed metamaterial.

Compositional engineering of perovskite materials for high-performance solar cells

Abstract: Inorganic–organic lead halide perovskite could be efficient when used as the light-harvesting component of solar cells; here incorporation of methylammonium lead bromide into formamidinium lead iodide stabilizes the perovskite and improves the power conversion efficiency of the solar cell up to 17.9 per cent. Inorganic–organic lead halide perovskites are currently attracting considerable interest for solar-cell applications. Most of the best performing perovskite solar cells to date have made use of methylammonium-based perovskites; formamidinium-based perovskites have also shown promise, but are not as stable. Now Nam Joong Jeon and colleagues show that the formamidinium-based perovskites can be stabilized by the addition of some methylammonium-based perovskite, and that solar cells incorporating the resulting compositionally tuned materials can reach new heights of efficiency. Of the many materials and methodologies aimed at producing low-cost, efficient photovoltaic cells, inorganic–organic lead halide perovskite materials1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17 appear particularly promising for next-generation solar devices owing to their high power conversion efficiency. The highest efficiencies reported for perovskite solar cells so far have been obtained mainly with methylammonium lead halide materials1,2,3,4,5,6,7,8,9,10. Here we combine the promising—owing to its comparatively narrow bandgap—but relatively unstable formamidinium lead iodide (FAPbI3) with methylammonium lead bromide (MAPbBr3) as the light-harvesting unit in a bilayer solar-cell architecture13. We investigated phase stability, morphology of the perovskite layer, hysteresis in current–voltage characteristics, and overall performance as a function of chemical composition. Our results show that incorporation of MAPbBr3 into FAPbI3 stabilizes the perovskite phase of FAPbI3 and improves the power conversion efficiency of the solar cell to more than 18 per cent under a standard illumination of 100 milliwatts per square centimetre. These findings further emphasize the versatility and performance potential of inorganic–organic lead halide perovskite materials for photovoltaic applications.

Formamidinium lead trihalide: a broadly tunable perovskite for efficient planar heterojunction solar cells

Abstract: Perovskite-based solar cells have attracted significant recent interest, with power conversion efficiencies in excess of 15% already superceding a number of established thin-film solar cell technologies. Most work has focused on a methylammonium lead trihalide perovskites, with a bandgaps of ∼1.55 eV and greater. Here, we explore the effect of replacing the methylammonium cation in this perovskite, and show that with the slightly larger formamidinium cation, we can synthesise formamidinium lead trihalide perovskites with a bandgap tunable between 1.48 and 2.23 eV. We take the 1.48 eV-bandgap perovskite as most suited for single junction solar cells, and demonstrate long-range electron and hole diffusion lengths in this material, making it suitable for planar heterojunction solar cells. We fabricate such devices, and due to the reduced bandgap we achieve high short-circuit currents of >23 mA cm−2, resulting in power conversion efficiencies of up to 14.2%, the highest efficiency yet for solution processed planar heterojunction perovskite solar cells. Formamidinium lead triiodide is hence promising as a new candidate for this class of solar cell.

Organometallic Halide Perovskites: Sharp Optical Absorption Edge and Its Relation to Photovoltaic Performance

Abstract: Solar cells based on organometallic halide perovskite absorber layers are emerging as a high-performance photovoltaic technology. Using highly sensitive photothermal deflection and photocurrent spectroscopy, we measure the absorption spectrum of CH3NH3PbI3 perovskite thin films at room temperature. We find a high absorption coefficient with particularly sharp onset. Below the bandgap, the absorption is exponential over more than four decades with an Urbach energy as small as 15 meV, which suggests a well-ordered microstructure. No deep states are found down to the detection limit of ∼1 cm–1. These results confirm the excellent electronic properties of perovskite thin films, enabling the very high open-circuit voltages reported for perovskite solar cells. Following intentional moisture ingress, we find that the absorption at photon energies below 2.4 eV is strongly reduced, pointing to a compositional change of the material.

Alternative Plasmonic Materials: Beyond Gold and Silver

Abstract: Materials research plays a vital role in transforming breakthrough scientific ideas into next-generation technology. Similar to the way silicon revolutionized the microelectronics industry, the proper materials can greatly impact the field of plasmonics and metamaterials. Currently, research in plasmonics and metamaterials lacks good material building blocks in order to realize useful devices. Such devices suffer from many drawbacks arising from the undesirable properties of their material building blocks, especially metals. There are many materials, other than conventional metallic components such as gold and silver, that exhibit metallic properties and provide advantages in device performance, design flexibility, fabrication, integration, and tunability. This review explores different material classes for plasmonic and metamaterial applications, such as conventional semiconductors, transparent conducting oxides, perovskite oxides, metal nitrides, silicides, germanides, and 2D materials such as graphene. This review provides a summary of the recent developments in the search for better plasmonic materials and an outlook of further research directions.

An Overview of the Theory and Applications of Metasurfaces: The Two-Dimensional Equivalents of Metamaterials

Abstract: Metamaterials are typically engineered by arranging a set of small scatterers or apertures in a regular array throughout a region of space, thus obtaining some desirable bulk electromagnetic behavior. The desired property is often one that is not normally found naturally (negative refractive index, near-zero index, etc.). Over the past ten years, metamaterials have moved from being simply a theoretical concept to a field with developed and marketed applications. Three-dimensional metamaterials can be extended by arranging electrically small scatterers or holes into a two-dimensional pattern at a surface or interface. This surface version of a metamaterial has been given the name metasurface (the term metafilm has also been employed for certain structures). For many applications, metasurfaces can be used in place of metamaterials. Metasurfaces have the advantage of taking up less physical space than do full three-dimensional metamaterial structures; consequently, metasurfaces offer the possibility of less-lossy structures. In this overview paper, we discuss the theoretical basis by which metasurfaces should be characterized, and discuss their various applications. We will see how metasurfaces are distinguished from conventional frequency-selective surfaces. Metasurfaces have a wide range of potential applications in electromagnetics (ranging from low microwave to optical frequencies), including: (1) controllable “smart” surfaces, (2) miniaturized cavity resonators, (3) novel wave-guiding structures, (4) angular-independent surfaces, (5) absorbers, (6) biomedical devices, (7) terahertz switches, and (8) fluid-tunable frequency-agile materials, to name only a few. In this review, we will see that the development in recent years of such materials and/or surfaces is bringing us closer to realizing the exciting speculations made over one hundred years ago by the work of Lamb, Schuster, and Pocklington, and later by Mandel'shtam and Veselago.