Compact nanophotonic elements exhibiting adaptable properties are essential components for the miniaturization of powerful optical technologies such as adaptive optics and spatial light modulators. ...While the larger counterparts typically rely on mechanical actuation, this can be undesirable in some cases on a microscopic scale due to inherent space restrictions. Here, we present a novel design concept for highly integrated active optical components that employs a combination of resonant plasmonic metasurfaces and the phase-change material Ge
Sb
Te
. In particular, we demonstrate beam switching and bifocal lensing, thus, paving the way for a plethora of active optical elements employing plasmonic metasurfaces, which follow the same design principles.
Graphene as a one-atom-thick planar sheet can support surface plasmons at infrared (IR) and terahertz (THz) frequencies, opening up exciting possibilities for the emerging research field of graphene ...plasmonics. Here, we theoretically report that a layered graphene-lens (GL) enables the enhancement of evanescent waves for near-field subdiffractive imaging. Compared to other resonant imaging devices like superlenses, the nonresonant operation of the GL provides the advantages of a broad intrinsic bandwidth and a low sensitivity to losses, while still maintaining a good subwavelength resolution of better than λ/10. Most importantly, thanks to the large tunability of the graphene, we show that our GL is a continuously frequency-tunable subwavelength-imaging device in the IR and THz regions, thus allowing for ultrabroadband spectral applications.
Hyperbolic materials exhibit sub-diffractional, highly directional, volume-confined polariton modes. Here we report that hyperbolic phonon polaritons allow for a flat slab of hexagonal boron nitride ...to enable exciting near-field optical applications, including unusual imaging phenomenon (such as an enlarged reconstruction of investigated objects) and sub-diffractional focusing. Both the enlarged imaging and the super-resolution focusing are explained based on the volume-confined, wavelength dependent propagation angle of hyperbolic phonon polaritons. With advanced infrared nanoimaging techniques and state-of-art mid-infrared laser sources, we have succeeded in demonstrating and visualizing these unexpected phenomena in both Type I and Type II hyperbolic conditions, with both occurring naturally within hexagonal boron nitride. These efforts have provided a full and intuitive physical picture for the understanding of the role of hyperbolic phonon polaritons in near-field optical imaging, guiding, and focusing applications.
Near-Field Microscopy Through a SiC Superlens Taubner, Thomas; Korobkin, Dmitriy; Urzhumov, Yaroslav ...
Science (American Association for the Advancement of Science),
09/2006, Letnik:
313, Številka:
5793
Journal Article
Recenzirano
The wave nature of light limits the spatial resolution in classical microscopy to about half of the illumination wavelength. Recently, a new approach capable of achieving subwavelength spatial ...resolution, called superlensing, was invented, challenging the already established method of scanning near-field optical microscopy (SNOM). We combine the advantages of both techniques and demonstrate a novel imaging system where the objects no longer need to be in close proxim-ity to a near-field probe, allowing for optical near-field microscopy of subsurface objects at sub-wavelength-scale lateral resolution.
Abstract Tailoring light-matter interaction is essential to realize nanophotonic components. It can be achieved with surface phonon polaritons (SPhPs), an excitation of photons coupled with phonons ...of polar crystals, which also occur in 2d materials such as hexagonal boron nitride or anisotropic crystals. Ultra-confined resonances are observed by restricting the SPhPs to cavities. Phase-change materials (PCMs) enable non-volatile programming of these cavities based on a change in the refractive index. Recently, the plasmonic PCM In 3 SbTe 2 (IST) was introduced which can be reversibly switched from an amorphous dielectric state to a crystalline metallic one in the entire infrared to realize numerous nanoantenna geometries. However, reconfiguring SPhP resonators to modify the confined polaritons modes remains elusive. Here, we demonstrate direct programming of confined SPhP resonators by phase-switching IST on top of a polar silicon carbide crystal and investigate the strongly confined resonance modes with scanning near-field optical microscopy. Reconfiguring the size of the resonators themselves result in enhanced mode confinements up to a value of $${{{\boldsymbol{\lambda }}}{{{\boldsymbol{/}}}{{{\boldsymbol{35}}}{{{\boldsymbol{.}}}$$ λ / 35 . Finally, unconventional cavity shapes with complex field patterns are explored as well. This study is a first step towards rapid prototyping of reconfigurable SPhP resonators that can be easily transferred to hyperbolic and anisotropic 2d materials.
Plasmonic antennas are crucial components for nano-optics and have been extensively used to enhance sensing, spectroscopy, light emission, photodetection, and others. Recently, there is a trend to ...search for new plasmonic materials with low intrinsic loss at new plasmon frequencies. As an alternative to metals, polar crystals have a negative real part of permittivity in the Reststrahlen band and support surface phonon polaritons (SPhPs) with weak damping. Here, we experimentally demonstrate the resonance of single circular microcavities in a thin gold film deposited on a silicon carbide (SiC) substrate in the mid-infrared range. Specifically, the negative permittivity of SiC leads to a well-defined, size-tunable SPhP resonance with a Q factor of around 60 which is much higher than those in surface plasmon polariton (SPP) resonators with similar structures. These infrared resonant microcavities provide new possibilities for widespread applications such as enhanced spectroscopy, sensing, coherent thermal emission, and infrared photodetectors among others throughout the infrared frequency range.
We show tuning of the resonance frequency of aluminum nanoantennas via variation of the refractive index n of a layer of phase-change material. Three configurations have been considered, namely, with ...the antennas on top of, inside, and below the layer. Phase-change materials offer a huge index change upon the structural transition from the amorphous to the crystalline state, both stable at room temperature. Since the imaginary part of their permittivity is negligibly small in the mid-infrared spectral range, resonance damping is avoided. We present resonance shifting to lower as well as to higher wavenumbers with a maximum shift of 19.3% and a tuning figure of merit, defined as the resonance shift divided by the full-width at half-maximum (FWHM) of the resonance peak, of 1.03.
Abstract
The high dielectric optical contrast between the amorphous and crystalline structural phases of non-volatile phase-change materials (PCMs) provides a promising route towards tuneable ...nanophotonic devices. Here, we employ the next-generation PCM In
3
SbTe
2
(IST) whose optical properties change from dielectric to metallic upon crystallization in the whole infrared spectral range. This distinguishes IST as a switchable infrared plasmonic PCM and enables a programmable nanophotonics material platform. We show how resonant metallic nanostructures can be directly written, modified and erased on and below the meta-atom level in an IST thin film by a pulsed switching laser, facilitating direct laser writing lithography without need for cumbersome multi-step nanofabrication. With this technology, we demonstrate large resonance shifts of nanoantennas of more than 4 µm, a tuneable mid-infrared absorber with nearly 90% absorptance as well as screening and nanoscale “soldering” of metallic nanoantennas. Our concepts can empower improved designs of programmable nanophotonic devices for telecommunications, (bio)sensing and infrared optics, e.g. programmable infrared detectors, emitters and reconfigurable holograms.
A conventional thermal emitter exhibits a broad emission spectrum with a peak wavelength depending upon the operation temperature. Recently, narrowband thermal emission was realized with periodic ...gratings or single microstructures of polar crystals supporting distinct optical modes. Here, we exploit the coupling of adjacent phonon-polaritonic nanostructures, demonstrating experimentally that the nanometer-scale gaps can control the thermal emission frequency while retaining emission line widths as narrow as 10 cm–1. This was achieved by using deeply subdiffractional bowtie-shaped silicon carbide nanoantennas. Infrared far-field reflectance spectroscopy, near-field optical nanoimaging, and full-wave electromagnetic simulations were employed to prove that the thermal emission originates from strongly localized surface phonon-polariton resonances of nanoantenna structures. The observed narrow emission line widths and exceptionally small modal volumes provide new opportunities for the user-design of near- and far-field radiation patterns for advancements in infrared spectroscopy, sensing, signaling, communications, coherent thermal emission, and infrared photodetection.
We demonstrate that scattering near-field microscopy (s-SNOM) can determine infrared “fingerprint” spectra of individual poly(methyl methacrylate) nanobeads and viruses as small as 18 nm. Amplitude ...and phase spectra are found surprisingly strong, even at a probed volume of only 10-20 l, and robust in regard to particle size and substrate. This makes infrared spectroscopic s-SNOM a versatile tool for chemical andin the case of proteinsecondary-structure identification.
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