19 research outputs found
Optical Properties of Bismuth Nanostructures Towards the Ultrathin Film Regime
Bulk bismuth presents outstanding optical properties, such as a giant
infrared refractive index (n near 10) and a negative ultraviolet visible
permittivity induced by giant interband electronic transitions. Although such
properties are very appealing for applications in nanophotonics, the dielectric
function of bismuth nanostructures has been scarcely studied. Here, we
determine by spectroscopic ellipsometry the far infrared to ultraviolet
dielectric function of pulsed laser deposited bismuth thin films with nominal
thickness tBi varied from near 10 nm to several tens of nm. For tBi above 15
nm, the films display a continuous structure and their dielectric function is
comparable with that of bulk bismuth. For tBi below 15 nm, the film structure
is discontinuous, and the dielectric function differs markedly from that of
bulk bismuth. It is proposed from FDTD simulations that this marked difference
arises mainly from effective medium effects induced by the discontinuous film
structure, where quantum electronic confinement does not play a dominant role.
This suggests that ultrathin and continuous bismuth films should present the
same outstanding optical properties as bulk bismuth for high performance
nanophotonic devices
Interband transitions in semi-metals, semiconductors, and topological insulators: A new driving force for plasmonics and nanophotonics
Plasmonic and Mie resonances in subwavelength nanostructures provide an
efficient way to manipulate light below the diffraction limit that has fostered
the growth of plasmonics and nanophotonics. Plasmonic resonances have been
mainly related with the excitation of free charge carriers, initially in
metals, and Mie resonances have been identified in Si nanostructures.
Remarkably, although much less studied, semi-metals, semiconductors and
topological insulators of the p-block enable plasmonic resonances without free
charge carriers and Mie resonances with enhanced properties compared with Si.
In this review, we explain how interband transitions in these materials show a
major role in this duality. We evaluate the plasmonic and Mie performance of
nanostructures made of relevant p-block elements and compounds, especially Bi,
and discuss their promising potential for applications ranging from switchable
plasmonics and nanophotonics to energy conversion, especially photocatalysis
Active analog tuning of the phase of light in the visible regime by bismuth-based metamaterials
Active and analog tuning of the phase of light is needed to boost the
switching performance of photonic devices. However, demonstrations of this type
of tuning in the pivotal visible spectral region are still scarce. Herein we
report active analog tuning of the phase of visible light reflected by a
bismuth-based metamaterial, enabled by a reversible solid-liquid transition.
This metamaterial, fabricated by a lithography-free approach, consists of
two-dimensional assemblies of polydisperse plasmonic bismuth nanostructures
embedded in a refractory and transparent aluminum oxide matrix. Analog tuning
of the phase is achieved by controlled heating of the metamaterial to melt a
fraction of the nanostructures. A maximum tuning of 320 deg (1.8pi) is observed
upon complete melting of the nanostructures at 230 degrees Celsius. This tuning
is reversible by cooling to 25 degrees Celsius. In addition, it presents a wide
hysteretic character due to liquid bismuth undercooling. This enables the phase
achieved by this analog approach to remain stable over a broad temperature
range upon cooling and until re-solidification occurs around 100 degrees
Celsius. Therefore, bismuth-based metamaterials are appealing for applications
including optical data storage with enhanced information density or bistable
photonic switching with a tunable "on" state
An all optical nanometric switch
[Poster of]: ¿SINFOTONes en el Año de la Luz?: Reunión de Jóvenes Investigadores SINFOTON: 1ª Feria de Otoño 2015, 23 de Octubre.Current requirements on information transfer, computation and storage demand new
counterparts to the electronic components. In particular, full-optical components are currently
explored. Different phenomena observed in the interaction of light with nanoparticles allow the
development of this concept. In this work, we explored the possibility of creating a full optical
nanometric switch to be the simplest part of the future family of components in optical
nanocircuits.
In 80's, Kerker et al [1] showed that the scattering of sub-wavelength particles can be directed
under certain conditions. In fact, a nanoparticle can accomplish a zero backscattering (ZB) or
minimum forward scattering (MF) depending on the relationship between its material, size and
incident wavelength. We have demonstrated that the Kerker conditions can be found in the visible
range for several usual semiconductor materials, as Silicon, Germanium, TiO2, GaAs, etc [2]. Playing
with sizes, it is possible to obtain nanoparticles satisfying either the ZB or the MF at the same
wavelength. Then, we have proposed a dimer of silicon nanoparticles [3] presenting such
combination of directional scattering in the visible range. This set can produce either a maximum or
a minimum of the scattered field in the area between the nanoparticles. As Kerkers' conditions are
very dependent on the wavelength, we propose that a modulation of the incident wavelength
can be used as switching parameter (Fig. 1). We have searched the optimum parameters of the
dimer setup, in wavelength, distance between particles and their sizes, in order to make easier the
fabrication for the Research Community to get an experimental Proof of Technology of these
simple designs.This work has been supported by Ministerio de EconomĂa y Competitividad of Spain (grants no. TEC2013-47342-C2-2-R, TEC2012-38901-C02-01 and no.TEC2013-50138-EXP) and
the R&D Program SINFOTON S2013/MIT-2790 of the Comunidad de Madrid.Publicad
Strain-Tuning of the Optical Properties of Semiconductor Nanomaterials by Integration onto Piezoelectric Actuators
The tailoring of the physical properties of semiconductor nanomaterials by
strain has been gaining increasing attention over the last years for a wide
range of applications such as electronics, optoelectronics and photonics. The
ability to introduce deliberate strain fields with controlled magnitude and in
a reversible manner is essential for fundamental studies of novel materials and
may lead to the realization of advanced multi-functional devices. A prominent
approach consists in the integration of active nanomaterials, in thin epitaxial
films or embedded within carrier nanomembranes, onto
Pb(Mg1/3Nb2/3)O3-PbTiO3-based piezoelectric actuators, which convert electrical
signals into mechanical deformation (strain). In this review, we mainly focus
on recent advances in strain-tunable properties of self-assembled InAs quantum
dots embedded in semiconductor nanomembranes and photonic structures.
Additionally, recent works on other nanomaterials like rare-earth and metal-ion
doped thin films, graphene and MoS2 or WSe2 semiconductor two-dimensional
materials are also reviewed. For the sake of completeness, a comprehensive
comparison between different procedures employed throughout the literature to
fabricate such hybrid piezoelectric-semiconductor devices is presented. Very
recently, a novel class of micro-machined piezoelectric actuators have been
demonstrated for a full control of in-plane stress fields in nanomembranes,
which enables producing energy-tunable sources of polarization-entangled
photons in arbitrary quantum dots. Future research directions and prospects are
discussed.Comment: review manuscript, 78 pages, 27 figure
Copernicus Ocean State Report, issue 6
The 6th issue of the Copernicus OSR incorporates a large range of topics for the blue, white and green ocean for all European regional seas, and the global ocean over 1993–2020 with a special focus on 2020
Bismuth-based Metamaterials: Fundamentals and Applications
Bismuth shows outstanding optical properties, including a metal-like response in the ultraviolet-visible and a dielectric character with giant refractive index in the infrared. We explain how this enables bismuth-based metamaterials to show a remarkable optical response over these spectral regions. Such response can be tuned in a static way by suitable metamaterial design and in a dynamic way by harnessing the solid-liquid transition of bismuth. We discuss the application of such metamaterials to information technology, energy harvesting and sensing