2,565 research outputs found
All-optical control of surface plasmons by second-harmonic generation
Light with light control of surface plasmon polaritons is theoretically
demonstrated. A barely simple and compact source of these waves consists in a
finite number of slits (evenly spaced) perforating a metal film. The system
scatters electromagnetic fields in one side of the metal film when it is
illuminated from the opposite side by a polarized light source. High intensity
light sources moreover efficiently generate light at second harmonic and higher
frequencies in the metal led by optical nonlinearities. It is shown how the
mixing of fields scattered by the slits from a weak beam at
wavelength, with the second harmonic fields generated by a high intensity beam, creates a destructive interference of surface plasmons in one of
the two possible directions of emission from the slits, while these are
enhanced along the opposite direction. The unidirectional launching of surface
plasmons is due to the different properties of symmetry at whether
they are linearly or nonlinearly generated. It is envisaged a nanodevice which
might allow sending digital information codified in the surface plasmon field
or be used to build ultra-narrow bandwidth surface plasmon frequency combs.Comment: 5 pages, 3 figures, Supplemental Materia
Second harmonic generation from metallic arrays of rectangular holes
The generation process of second harmonic (SH) radiation from holes
periodically arranged on a metal surface is investigated. Three main modulating
factors affecting the optical response are identified: the near-field
distribution at the wavelength of the fundamental harmonic, how SH light
couples to the diffraction orders of the lattice, and its propagation
properties inside the holes. It is shown that light generated at the second
harmonic can excite electromagnetic modes otherwise inaccessible in the linear
regime under normal incidence illumination. It is demonstrated that the
emission of SH radiation is only allowed along off-normal paths precisely due
to that symmetry. Two different regimes are studied in the context of
extraordinary optical transmission, where enhanced linear transmission either
occurs through localized electromagnetic modes or is aided by surface plasmon
polaritons (SPPs). While localized resonances in metallic hole arrays have been
previously investigated, the role played by SPPs in SH generation has not been
addressed so far. In general, good agreement is found between our calculations
(based on the finite difference time domain method) and the experimental
results on localized resonances, even though no free fitting parameters were
used in describing the materials. It is found that SH emission is strongly
modulated by enhanced fields at the fundamental wavelength (either localized or
surface plasmon modes) on the glass metal interface. This is so in the
transmission side but also in reflection, where emission can only be explained
by an efficient tunneling of SH photons through the holes from the output to
the input side. Finally, the existence of a dark SPP at the fundamental field
is identified through a noninvasive method for the first time, by analyzing the
efficiency and far-field pattern distribution in transmission at the second
harmonic.Comment: This paper was published in JOSA B and is made available as an
electronic reprint with the permission of OSA. The paper can be found at the
following URL on the OSA website:
http://www.opticsinfobase.org/josab/abstract.cfm?URI=josab-32-1-15.
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Terahertz gas sensor based on absorption-induced transparency
A system for the detection of spectral signatures of gases at the Terahertz regime is presented. The system consists in an initially opaque holey metal film whereby the introduction of a gas provokes the appearance of spectral features in transmission and reflection, due to the phenomenom of absorption-induced transparency (AIT). The peaks in transmission and dips in reflection observed in AIT occur close to the absorption energies of the molecules, hence its name. The presence of the gas would be thus revealed as a strong drop in reflectivity measurements at one (or several) of the gas absorption resonances. As a proof of principle, we theoretically demonstrate how the AIT-based sensor would serve to detect tiny amounts of hydrocyanic acid
Coherent Control of Light Scattering from Nanostructured Materials by Second-Harmonic Generation
We introduce an active, all-optical method for controlling the intensity and directionality of light scattering from single nanostructures. The method is based on the coherent interplay between linear light scattering and second-harmonic generation. The intensity and directionality of scattered light can be controlled by the phase delay and the relative angle between excitation beams. We discuss the principle of this coherent control technique and perform numerical model calculations
Solving differential equations with Deep Learning: a beginner's guide
The research in Artificial Intelligence methods with potential applications
in science has become an essential task in the scientific community last years.
Physics Informed Neural Networks (PINNs) is one of this methods and represent a
contemporary technique that is based on the fundamentals of neural networks to
solve differential equations. These kind of networks have the potential to
improve or complement classical numerical methods in computational physics,
making them an exciting area of study. In this paper, we introduce PINNs at an
elementary level, mainly oriented to physics education so making them suitable
for educational purposes at both undergraduate and graduate levels. PINNs can
be used to create virtual simulations and educational tools that aid in
understating complex physical concepts and processes where differential
equations are involved. By combining the power of neural networks with physics
principles, PINNs can provide an interactive and engaging learning experience
that can improve students' understanding and retention of physics concepts in
higher education
Influence of material properties on extraordinary optical transmission through hole arrays
We present a theoretical study, based on the finite difference time domain method, of the optical response of circular hole arrays drilled in several metal films (Ag, Au, Cu, Al, Ni, Cr, and W). Two series of structures are studied. In the first one, transmittance peaks are analyzed as all geometrical parameters defining the system are scaled, except for the metal thickness which is kept constant, showing good agreement with existing experimental data. In the second series, the metal thickness is also scaled. This allows a clear distinction in the behavior of different metals: Ag, Au, and Cu show even larger transmittance peaks than hole arrays in a perfect conductor with the same nominal parameters. This is due to both a larger effective hole area and smaller absorption. In the case of Ni and Cr, the transmittance is much smaller due to absorption. Band structure calculations confirm that surface electromagnetic modes sustained by the perforated metal film are responsible for the extraordinary optical transmission phenomenon
Theory of light transmission through an array of rectangular holes
In a two-dimensional array of rectangular holes perforated on a metallic film, two mechanisms leading to enhanced transmission of light operate: excitation of surface plasmon polaritons (SPPs) and localized resonances that are also present in single holes. In this paper, we analyze theoretically how the two mechanisms evolve and mix when the period of the array is varied. We also demonstrate that absorption in the metal is the main limiting factor for the SPP-based enhanced transmission
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