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Author

Rainer Jacob

Bio: Rainer Jacob is an academic researcher from Helmholtz-Zentrum Dresden-Rossendorf. The author has contributed to research in topics: Near-field scanning optical microscope & Spectroscopy. The author has an hindex of 4, co-authored 5 publications receiving 178 citations.

Papers
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Journal ArticleDOI
TL;DR: A superlens for electric evanescent fields with low losses using perovskites in the mid-infrared regime using near-field microscopy with a tunable free-electron laser to address precisely the polariton modes, which are critical for super-resolution imaging.
Abstract: A planar slab of negative-index material works as a superlens with sub-diffraction-limited resolution, as propagating waves are focused and, moreover, evanescent waves are reconstructed in the image plane. Here we demonstrate a superlens for electric evanescent fields with low losses using perovskites in the mid-infrared regime. The combination of near-field microscopy with a tunable free-electron laser allows us to address precisely the polariton modes, which are critical for super-resolution imaging. We spectrally study the lateral and vertical distributions of evanescent waves around the image plane of such a lens, and achieve imaging resolution of λ/14 at the superlensing wavelength. Interestingly, at certain distances between the probe and sample surface, we observe a maximum of these evanescent fields. Comparisons with numerical simulations indicate that this maximum originates from an enhanced coupling between probe and object, which might be applicable for multifunctional circuits, infrared spectroscopy and thermal sensors.

105 citations

Journal ArticleDOI
TL;DR: Using scattering-type near-field infrared microscopy in combination with a free-electron laser, intersublevel transitions in buried single InAs quantum dots are investigated and signals from bound-to-bound transitions of single electrons in a probe volume of the order of (100 nm)(3).
Abstract: Using scattering-type near-field infrared microscopy in combination with a free-electron laser, intersublevel transitions in buried single InAs quantum dots are investigated. The experiments are performed at room temperature on doped self-assembled quantum dots capped with a 70 nm GaAs layer. Clear near-field contrast of single dots is observed when the photon energy of the incident beam matches intersublevel transition energies, namely the p-d and s-d transition of conduction band electrons confined in the dots. The observed room-temperature line width of 5–8 meV of these resonances in the mid-infrared range is significantly below the inhomogeneously broadened spectral lines of quantum dot ensembles. The experiment highlights the strength of near-field microspectroscopy by demonstrating signals from bound-to-bound transitions of single electrons in a probe volume of the order of (100 nm)3.

50 citations

Journal ArticleDOI
TL;DR: A combination of a scattering-type near-field infrared microscope with a free-electron laser as an intense, tunable radiation source to spatially and spectrally resolve buried doped layers in silicon yields quantitatively correct values for the concentration of the activated carriers.
Abstract: We use a combination of a scattering-type near-field infrared microscope with a free-electron laser as an intense, tunable radiation source to spatially and spectrally resolve buried doped layers in silicon. To this end, boron implanted stripes in silicon are raster scanned at different wavelengths in the range from 10 to 14 µm. An analysis based on a simple Drude model for the dielectric function of the sample yields quantitatively correct values for the concentration of the activated carriers. In a control experiment at the fixed wavelength of 10.6 µm, interferometric near-field signals are recorded. The phase information gained in this experiment is fully consistent with the carrier concentration obtained in the spectrally resolved experiments.

25 citations

Journal ArticleDOI
TL;DR: In this article, the lateral, vertical, and spectral field distribution of three different perovskite-based superlenses by means of scattering-type near-field microscopy was studied.
Abstract: Superlenses create sub-diffraction-limit images by reconstructing the evanescent fields arising from an object. We study the lateral, vertical, and spectral field distribution of three different perovskite-based superlenses by means of scattering-type near-field microscopy. Sub-diffraction-limit resolution is observed for all samples with an image contrast depending on losses such as scattering and absorption. For the three lenses superlensing is observed at slightly different frequencies resulting in an overall broad frequency range of 3.6 THz around 20 THz.

14 citations

Proceedings ArticleDOI
28 Oct 2010
TL;DR: In this paper, a scattering-type scanning near-field optical micro-spectroscopy (s-SNOM) investigations successfully operated in the THz range with a wavelength independent spatial resolution of < 150 nm.
Abstract: We present scattering-type scanning near-field optical micro-spectroscopy (s-SNOM) investigations successfully operated in the THz range with a wavelength independent spatial resolution of < 150 nm. As a variable and monochromatic radiation source we use the free-electron laser (FELBE) located at the Forschungszentrum Dresden-Rossendorf (FZD) tunable over the wavelength range from 4–250 μm.

2 citations


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Journal ArticleDOI
TL;DR: This review explores different material classes for plasmonic and metamaterial applications, such as conventional semiconductors, transparent conducting oxides, perovskiteOxides, metal nitrides, silicides, germanides, and 2D materials such as graphene.
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.

1,836 citations

Journal ArticleDOI
TL;DR: In this paper, the authors provide details of fabrication and characterization of these new materials and discuss their suitability for a number of metamaterial and plasmonic applications, as well as their properties.
Abstract: As alternatives to conventional metals, new plasmonic materials offer many advantages in the rapidly growing fields of plasmonics and metamaterials. These advantages include low intrinsic loss, semiconductor-based design, compatibility with standard nanofabrication processes, tunability, and others. Transparent conducting oxides such as Al:ZnO, Ga:ZnO and indium-tin-oxide (ITO) enable many high-performance metamaterial devices operating in the near-IR. Transition-metal nitrides such as TiN or ZrN can be substitutes for conventional metals in the visible frequencies. In this paper we provide the details of fabrication and characterization of these new materials and discuss their suitability for a number of metamaterial and plasmonic applications.

782 citations

Journal ArticleDOI
TL;DR: In this article, the main types and mechanisms of magnetoelectric interactions and conditions of their origin are discussed, as well as potentially practical materials that display magneto-lectric properties at room temperature.
Abstract: The last decade has witnessed a significant growth of research into materials with coupled magnetic and electric properties. Reviewed here are the main types and mechanisms of magnetoelectric interactions and conditions of their origin. Special attention is given to potentially practical materials that display magnetoelectric properties at room temperature. Example applications of magnetoelectric materials and multiferroics in information and energy saving technologies are discussed.

477 citations

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate that hexagonal boron nitride, a natural mid-infrared hyperbolic material, can act as a "hyper-focusing lens" and as a multi-mode waveguide.
Abstract: Uniaxial materials whose axial and tangential permittivities have opposite signs are referred to as indefinite or hyperbolic media. In such materials, light propagation is unusual leading to novel and often non-intuitive optical phenomena. Here we report infrared nano-imaging experiments demonstrating that crystals of hexagonal boron nitride, a natural mid-infrared hyperbolic material, can act as a 'hyper-focusing lens' and as a multi-mode waveguide. The lensing is manifested by subdiffractional focusing of phonon-polaritons launched by metallic disks underneath the hexagonal boron nitride crystal. The waveguiding is revealed through the modal analysis of the periodic patterns observed around such launchers and near the sample edges. Our work opens new opportunities for anisotropic layered insulators in infrared nanophotonics complementing and potentially surpassing concurrent artificial hyperbolic materials with lower losses and higher optical localization.

379 citations

Journal ArticleDOI
TL;DR: In this letter, a metal is replaced with aluminum-doped zinc oxide as a new plasmonic material and negative refraction is experimentally demonstrated in an Al:ZnO/ ZnO metamaterial in the near-infrared range.
Abstract: Noble metals such as gold and silver are conventionally used as the primary plasmonic building blocks of optical metamaterials. Making subwavelength-scale structural elements from these metals not only seriously limits the optical performance of a device due to high absorption, it also substantially complicates the manufacturing process of nearly all metamaterial devices in the optical wavelength range. As an alternative to noble metals, we propose to use heavily doped oxide semiconductors that offer both functional and fabrication advantages in the near-infrared wavelength range. In this letter, we replace a metal with aluminum-doped zinc oxide as a new plasmonic material and experimentally demonstrate negative refraction in an Al:ZnO/ZnO metamaterial in the near-infrared range.

323 citations