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Sökning: L773:1094 4087 > Örebro universitet

  • Resultat 1-7 av 7
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1.
  • Kotlyar, Oleksandr, 1982-, et al. (författare)
  • Convolutional long short-term memory neural network equalizer for nonlinear Fourier transform-based optical transmission systems
  • 2021
  • Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 29:7, s. 11254-11267
  • Tidskriftsartikel (refereegranskat)abstract
    • We evaluate improvement in the performance of the optical transmission systems operating with the continuous nonlinear Fourier spectrum by the artificial neural network equalisers installed at the receiver end. We propose here a novel equaliser designs based on bidirectional long short-term memory (BLSTM) gated recurrent neural network and compare their performance with the equaliser based on several fully connected layers. The proposed approach accounts for the correlations between different nonlinear spectral components. The application of BLSTM equaliser leads to a 16x improvement in terms of bit-error rate (BER) compared to the non-equalised case. The proposed equaliser makes it possible to reach the data rate of 170 Gbit/s for one polarisation conventional nonlinear Fourier transform (NFT) based system at 1000 km distance. We show that our new BLSTM equalisers significantly outperform the previously proposed scheme based on a feed-forward fully connected neural network. Moreover, we demonstrate that by adding a 1D convolutional layer for the data pre-processing before BLSTM recurrent layers, we can further enhance the performance of the BLSTM equaliser, reaching 23x BER improvement for the 170 Gbit/s system over 1000 km, staying below the 7% forward error correction hard decision threshold (HD-FEC).
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2.
  • Lehmuskero, Anni, et al. (författare)
  • Plasmonic particles set into fast orbital motion by an optical vortex beam
  • 2014
  • Ingår i: Optics express. - : The Optical Society. - 1094-4087. ; 22:4, s. 4349-4356
  • Tidskriftsartikel (refereegranskat)abstract
    • We optically trap plasmonic gold particles in two dimensions and set them into circular motion around the optical axis using a helically phased vortex laser beam. The orbiting frequency of the particles reaches 86 Hz, which corresponds to a particle velocity of the order 1 mm per second, for an incident laser power of a few tens of milliwatts. The experimentally determined orbiting frequencies are found to be well in line with the notion that the beam carries an orbital angular momentum of ħl per photon.
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3.
  • Miljkovic, Vladimir, 1982, et al. (författare)
  • Mode-specific directional emission from hybridized particle-on-a-film plasmons
  • 2011
  • Ingår i: Optics Express. - 1094-4087. ; 19:14, s. 12856-12864
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate the electromagnetic interaction between a gold nanoparticle and a thin gold film on a glass substrate. The coupling between the particle plasmons and the surface plasmon polaritons of the film leads to the formation of two localized hybrid modes, one low-energy. film-like. plasmon and one high-energy plasmon dominated by the nanoparticle. We find that the two modes have completely different directional scattering patterns on the glass side of the film. The high-energy mode displays a characteristic dipole emission pattern while the low-energy mode sends out a substantial part of its radiation in directions parallel to the particle dipole moment. The relative strength of the two radiation patterns vary strongly with the distance between the particle and the film, as determined by the degree of particle-film hybridization. (C) 2011 Optical Society of America
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4.
  • Miljkovic, Vladimir, 1982, et al. (författare)
  • Simulating light scattering from supported plasmonic nanowires
  • 2012
  • Ingår i: Optics Express. - : Optical Society of America. - 1094-4087 .- 1094-4087. ; 20:10, s. 10816-10826
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a method for calculating the differential scattering cross sections from nanostructures close to an interface separating two semi-infinitive dielectric media. The method combines a fast finite element software (Comsol multiphysics), used for calculations of the fields around and inside the structure, and the Green's functions method, which is used to find the far field distribution from the calculated total fields inside the nanostructure. We apply the method to calculations of scattering spectra from silver nanowires supported by an air-glass interface, a system that is of high current interest in relation to various nanophotonics applications. The results are analyzed in relation to analytical models and compared to experimentally measured spectra, to which we find a good agreement.
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5.
  • Odebo Länk, Nils, 1988, et al. (författare)
  • Directional scattering and multipolar contributions to optical forces on silicon nanoparticles in focused laser beams
  • 2018
  • Ingår i: Optics Express. - : Optical Society of America. - 1094-4087 .- 1094-4087. ; 26:22, s. 29074-29085
  • Tidskriftsartikel (refereegranskat)abstract
    • Nanoparticles made of high index dielectric materials have seen a surge of interest and have been proposed for various applications, such as metalenses, light harvesting and directional scattering. With the advent of fabrication techniques enabling colloidal suspensions, the prospects of optical manipulation of such nanoparticles becomes paramount. High index nanoparticles support electric and magnetic multipolar responses in the visible regime and interference between such modes can give rise to highly directional scattering, in particular a cancellation of back-scattered radiation at the first Kerker condition. Here we present a study of the optical forces on silicon nanoparticles in the visible and near infrared calculated using the transfer matrix method. The zero-backscattering Kerker condition is investigated as an avenue to reduce radiation pressure in an optical trap. We find that while asymmetric scattering does reduce the radiation pressure, the main determining factor of trap stability is the increased particle response near the geometric resonances. The trap stability for non-spherical silicon nanoparticles is also investigated and we find that ellipsoidal deformation of spheres enables trapping of slightly larger particles.
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6.
  • Pervishko, Anastasiia A., et al. (författare)
  • Localized surface electromagnetic waves in CrI3-based magnetophotonic structures
  • 2020
  • Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 28:20, s. 29155-29165
  • Tidskriftsartikel (refereegranskat)abstract
    • Resulting from strong magnetic anisotropy two-dimensional ferromagnetism was recently shown to be stabilized in chromium triiodide, CrI3, in the monolayer limit. While its properties remain largely unexplored, it provides a unique material-specific platform to unveil its electromagnetic properties associated with coupling of modes. Indeed, trigonal symmetry in the presence of out-of-plane magnetization results in a non-trivial structure of the conductivity tensor, including the off-diagonal terms. In this paper, we study the surface electromagnetic waves localized in a CrI3-based structure using the results of ab initio calculations for the CrI3 conductivity tensor. In particular, we provide an estimate for the critical angle corresponding to the surface plasmon polariton generation in the Kretschmann-Raether configuration by a detailed investigation of reflectance spectrum as well as the magnetic field distribution for different CrI3 layer thicknesses. We also study the bilayer structure formed by two CrI3 layers separated by a SiO2 spacer and show that the surface plasmon resonance can be achieved at the interface between CrI3 and air depending on the spacer thickness.
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7.
  • Sepulveda, Borja, et al. (författare)
  • Shape effects in the localized surface plasmon resonance of single nanoholes in thin metal films
  • 2008
  • Ingår i: Optics Express. - Washington, DC : Optical Society of America. - 1094-4087. ; 16:8, s. 5609-5616
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on the polarization-dependent optical response of elongated nanoholes in optically thin gold films. We measured elastic scattering spectra of spatially isolated ellipsoidal nanoholes with varying aspect ratio and compared the results to electrodynamic simulations. Both experiments and theory show that the plasmon mode that is polarized parallel to the short axis of the ellipsoidal hole red-shifts with increasing aspect ratio. This behavior is completely opposite to the case of elongated metal particles. We present a simple analytical model that qualitatively explains the observations in terms of the different orientations of the induced dipole moments in holes and particles.
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  • Resultat 1-7 av 7

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