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  • 1. Almeida, J. M. P.
    et al.
    Tribuzi, V.
    Fonseca, R. D.
    Otuka, A. J. G.
    Ferreira, P. H. D.
    Mastelaro, V. R.
    Brajato, P.
    Hernandes, A. C.
    Dev, Apurba
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Halvledarmaterial, HMA. Universidade de São Paulo, Brazil.
    Voss, T.
    Correa, D. S.
    Mendonca, C. R.
    Femtosecond laser processing of glassy and polymeric matrices containing metals and semiconductor nanostructures2013Inngår i: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 35, nr 12, s. 2643-2648Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Tailoring properties of materials by femtosecond laser processing has been proposed in the last decade as a powerful approach for technological applications, ranging from optics to biology. Although most of the research output in this field is related to femtosecond laser processing of single either organic or inorganic materials, more recently a similar approach has been proposed to develop advanced hybrid nanomaterials. Here, we report results on the use of femtosecond lasers to process hybrid nanomaterials, composed of polymeric and glassy matrices containing metal or semiconductor nanostructures. We present results on the use of femtosecond pulses to induce Cu and Ag nanoparticles in the bulk of borate and borosilicate glasses, which can be applied for a new generation of waveguides. We also report on 3D polymeric structures, fabricated by two-photon polymerization, containing Au and ZnO nanostructures, with intense two-photon fluorescent properties. The approach based on femtosecond laser processing to fabricate hybrid materials containing metal or semiconductor nanostructures is promising to be exploited for optical sensors and photonics devices.

  • 2.
    Bagheri, Shervin
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik. Photonics Laboratory, Physics Department, Kharazmi University, Tehran, Iran.
    Liu, Q.ingyun
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Bergstrand, Jan
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Pu, R.
    Centre for Optical and Electromagnetic Research, Guangdong Provincial Key Laboratory of Optical Information.
    Zhan, Q.
    Centre for Optical and Electromagnetic Research, Guangdong Provincial Key Laboratory of Optical Information.
    Ara, M. H. M.
    Photonics Laboratory, Physics Department, Kharazmi University, Tehran, Iran.
    Ågren, Hans
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. College of Chemistry and Chemical Engineering, Henan University, Kaifeng, Henan 475004, China.
    Liu, Haichun
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Widengren, Jerker
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Change in the emission saturation and kinetics of upconversion nanoparticles under different light irradiations2019Inngår i: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 97, artikkel-id 109389Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nd3+-sensitized upconversion nanoparticles (UCNPs) can be excited by both 980 and 808 nm light, which is regarded as a particularly advantageous property of these particles. In this work, we demonstrate that the nanoparticles can exhibit significantly different response when excited at these two excitation wavelengths, showing dependence on the intensity of the excitation light and the way it is distributed in time. Specifically, with 808 nm excitation saturation in the emitted luminescence is more readily reached with increasing excitation intensities than upon 980 nm excitation. This is accompanied by delayed upconversion luminescence (UCL) kinetics and weaker UCL intensities. The different luminescence response at 808 and 980 nm excitation reported in this work is relevant in a manifold of applications using UCNPs as labels and sensors. This could also open new possibilities for multi-wavelength excitable UCNPs for upconversion color display and in laser-scanning microscopy providing selective readouts and sub-sectioning of samples.

  • 3. Bolanos, Western
    et al.
    Carvajal, Joan J.
    Mateos, Xavier
    Cinta Pujol, Maria
    Thilmann, Nicky
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Lifante, Gines
    Aguilo, Magdalena
    Diaz, Francesc
    Epitaxial layers of KY1-x-yGdxLuy(WO4)(2) doped with Er3+ and Tm3+ for planar waveguide lasers2010Inngår i: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 32, nr 3, s. 469-474Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Here we show the results we obtained in the fabrication of planar wave guide lasers based on monoclinic double tungstates doped with Er3+ and Tm3+. We have successfully introduced these ions into the lattice matched KY0.59Gd0.19Lu0.22(WO4)(2) epitaxial layers grown on KY(WO4)(2) substrates without loss of optical quality and keeping a high refractive index contrast between the epitaxial layer and the substrate. We characterized the waveguiding properties of these epitaxial layers at lambda = 632.8 nm by dark modes spectroscopy, and we showed that these waveguides can support several TE and TM modes. Spectroscopic characterization of the active lanthanide ions in these crystals is also presented.

  • 4. Cao, X.
    et al.
    Wang, Z. G.
    He, Sailing
    Zhan, L.
    Xia, Y. X.
    Optical and structural characterization of annealed proton exchange waveguides in Y-cut MgO: LiNbO32005Inngår i: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 27, nr 10, s. 1596-1601Artikkel i tidsskrift (Fagfellevurdert)
  • 5. Karpus, V.
    et al.
    Suchodolskis, Arturas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Taulavicius, J.
    Karlsson, Ulf O.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Assmus, W.
    Bruehne, S.
    Uhrig, E.
    Photoemission spectroscopy study of si-ZnMgHo quasicrystals2008Inngår i: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 30, nr 5, s. 690-692Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The results of photoemission spectroscopy of the simple-icosahedral single-grain ZnMgHo quasicrystals are presented. Synchrotron radiation photoemission measurements were performed on in situ cleaved samples at 10(-10) mbar pressure and low, 160 K, temperature. The valence band photoemission spectra measured reveal a simple metal type valence band with a distinct Fermi edge and a sharp pseudogap feature, which originates from the van Hove singularities in the density of states. The photoemission spectra of the Mg 2p core level show the coordination shifts of Mg 2p, spin-orbit doublet due to inequivalent Mg sites in the quasicrystalline lattice.

  • 6.
    Pasiskevicius, Valdas
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Strömqvist, Gustav
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Quasi-phase matched nonlinear media: Progress towards nonlinear optical engineering2012Inngår i: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 34, nr 3, s. 513-523Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Nonlinear optics has been enabled by the invention of the laser 50 years ago, and since then both technologies evolved together complementing and enabling each other. In this paper we attempt to briefly overview the historic development of second-order nonlinear materials and try to discern the trends which might dominate developments in the future. The advent of methods of quasi-phase matching and added degrees of freedom in managing three-wave mixing processes pushed the field of nonlinear optics into the realm of engineering. This trend, we believe will continue in the future. In this text we give a short description of design principles of one-dimensional and two-dimensional quasi-phase matched structures and emphasize the increased functionality afforded by such structures. We also overview the nonlinear media where engineering of nonlinear interactions has been demonstrated with the primary focus on ferroelectric and semiconductor nonlinear crystals.

  • 7.
    Pitois, Claire
    et al.
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Vestberg, Robert
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Rodlert, Marlene
    Malmström, Eva
    KTH, Tidigare Institutioner                               , Fiber- och polymerteknologi.
    Hult, Anders
    KTH, Tidigare Institutioner                               , Polymerteknologi.
    Lindgren, M.
    Fluorinated dendritic polymers and dendrimers for waveguide applications2003Inngår i: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 21, nr 1-3, s. 499-506Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    I Fluorinated hyperbranched polymers and dendrimers with low optical losses and functionality to modify refractive index and add a cross-linking unit were developed. The results of refractive index. measurements indicate a tunability of the refractive index between approximately 1.5 and 1.6, and optical losses below 0.5 dB/cm at 1550 nm. Dendrimers with similar, surface group structure and possibility to surface functionalization were prepared using a lanthanide. cation as focal point. Results on luminescent properties in the NIR and IR regions were measured for lanthanide ions such as Nd3+ and Er3+, showing characteristic emission bands at 1.06, 1.3 and 1.5 mum. The associated absorption and excitation spectra were found similar to those of the corresponding ions in optical glasses.

  • 8.
    Souza Dantas, Nilton
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Ferreira da Silva, Antonio
    Persson, Clas
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Electronic band -edge properties of rock salt PbY and SnY (Y = S, Se, and Te)2008Inngår i: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 30, nr 9, s. 1451-1460Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The electronic band-edges of lead chalcogenides PbY and tin chalcogenides SnY (where Y = S, Se, and Te) are investigated by the means of a full-potential linearized augmented plane wave (FPLAPW) method and the local density approximation (LDA). All six chalcogenide binaries have similar electronic structures and density-of-states, but there are differences in the symmetry of the band-edge states at and near the Brillouin zone L-point. These differences give the characteristic composition, pressure, and temperature dependences of the energy gap in Pb1-xSnxY alloys.We find that: (1) SnY are zero-gap semiconductors E-g = 0 if the spin-orbit (SO) interaction is excluded. The reason for this is that the conduction band (CB) and the valence band (VB) cross along the Q equivalent to LW line. (2) Including the SO interaction splits this crossing and creates a direct gap along the Q-line, thus away from the L symmetry point. Hence, the fundamental band gap E-g in SnY is induced by the SO interaction and the energy gap is rather small Eg approximate to 0.2-0.3 eV. At the L-point, the CB state has symmetric L-4(+) and the VB state is antisymmetric L-4(-) thereby the L-point pressure coefficient partial derivative E-g(L)/partial derivative p is a positive quantity. (3) PbY have a direct band gap at the L-point both when SO coupling is excluded and included. In contrast to SnY, the SO interaction decreases the gap energy in PbY. (4) Including the SO interaction, the LDA yields incorrect symmetries of the band-edge states at the L-point; the CB state has L-4(+) and the VB state has L-4(-) symmetry. However, a small increase of the cell volume corrects this LDA failure, producing an antisymmetric CB state and a symmetric VB state, and thereby also yields the characteristic negative pressure coefficient partial derivative E-g(L)/partial derivative p in agreement with experimental findings. (5) Although PbY and SnY have different band-edge physics at their respective equilibrium lattice constants, the change of the band-edges with respect to cell volume is qualitatively the same for all six chalcogenides. (6) Finally, in the discussion of the symmetry of the band edges, it is important to clearly state the chosen unit cell origin; a shift by (a/2,0,0) changes the labeling L-4(+) double left right arrow L-4(-) of the irreducible representations.

  • 9. Srimathi, K.
    et al.
    Hussain, Tanveer
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. bCondensed Matter Theory Group, Materials Theory Division, Department of Physics and Astronomy, Uppsala University, P.O Box 530, Uppsala, S75121, Sweden.
    Panigrahi, P.
    Subramaniam, N. G.
    Ahuja, Rajeev
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. Condensed Matter Theory Group, Materials Theory Division, Department of Physics and Astronomy, Uppsala University, P.O Box 530, Uppsala, S75121, Sweden.
    Influence of Sodium Iodide doped polypyrrole on green synthesized aluminum doped ZnO for the enhanced charge separation at the interface2020Inngår i: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 99, artikkel-id 109568Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Different Concentration of Aluminum (1, 3, 5%) was doped in ZnO by green synthesis method using environmental friendly cucum sativa fruit pulp extract as capping agent. Increase in crystallinity was observed for higher concentration of Aluminum in ZnO by X-ray diffraction (XRD). With the increase in Al percentage, band gap gets reduced from 3.14eV to 3.01eV, due to band tailing effect. On the other hand, Polypyrrole(PPy) and Sodium iodide(NaI) doped PPy powder synthesized by chemical polymerization method produced a band gap of 2.83eV and 2.57eV respectively. A simple and economical Successive ionic layer adsorption and reaction (SILAR) method was employed to fabricate 5% Al doped ZnO/NaI-PPy nanocomposite thin film. Characterization of the ZnO reveal enhanced crystallinity, spherical morphology and low band gap which has an influence in the Photoluminescence quenching of the nanocomposite thin film. To reveal the electronic property of ZnO with Al using density functional theory (DFT) was performed. Reduction in band gap well agreed with experimental finding. Our findings suggest that nanocomposite thin film can be fabricated with improved charge separation at the interface which can find application in Photo catalysis, hybrid solar cell and optoelectronic devices.

  • 10.
    Sychugov, Ilya
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Juhasz, Robert
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Galeckas, Augustinas
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Valenta, Jan
    Linnros, Jan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Single dot optical spectroscopy of silicon nanocrystals: Low temperature measurements2005Inngår i: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 27, nr 5, s. 973-976Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Single dot spectroscopy allows studying properties of a single nanocrystal avoiding inhomogeneous broadening of the emission band. Here, data obtained by this technique for Si nanocrystals fabricated by electron beam lithography, plasma etching and subsequent size-reduction by oxidation are presented. First, blinking (on–off intermittence) of the luminescence was observed for most individual nanocrystals, although some exhibited relatively stable luminescence. As a result of the quantum confinement effect spectra with different emission wavelengths for different nanocrystals were recorded. While at room temperature the full width at half-maximum of the nanocrystal emission peaks was measured to be 100–150 meV, at 80 K the linewidth for some dots appeared to be about 25 meV only. The observed temperature dependence of the homogeneous linewidth may lead to an understanding of the exciton–phonon interaction in indirect band-gap quantum dots.

  • 11. Valenta, J.
    et al.
    Janda, P.
    Dohnalova, K.
    Niznansky, D.
    Vacha, F.
    Linnros, Jan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Colloidal suspensions of silicon nanocrystals: from single nanocrystals to photonic structures2005Inngår i: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 27, nr 5, s. 1046-1049Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Colloidal suspesions of Si nanocrystals (NCs) are prepared from light-emitting porous Si grains obtained by mechanical pulverization of electrochemically etched layers. Sedimented and/or filtered Si NCs sols reveal a green photoluminescence (PL) band around 530nm, which is interpreted as radiative recombination of electron-hole pairs inside Si NCs with diameter about 2nm. These colloidal solutions have multiple advantages for both fundamental investigations and for nanotechnology. In one extreme, single molecule spectroscopy techniques can be applied to investigate PL of single grains of Si NCs dispersed on substrates from highly diluted solutions. On the other hand, concentrated suspensions enable us to fabricate bulk samples with embedded Si NCs or to prepare self-organised nanostructures on surfaces.

  • 12. Valenta, J.
    et al.
    Lalic, N.
    Linnros, Jan
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Electroluminescence microscopy and spectroscopy of silicon nanocrystals in thin SiO2 layers2001Inngår i: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 17, nr 02-jan, s. 45-50Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stable continuously operable electroluminescent diodes have been fabricated by Sii-ion implantation and annealing of thin SiO2 layers on a silicon substrate. The external quantum efficiency of the device is reaching 3 x 10(-5) for the best diodes. Electroluminescence (EL) emission band is wide and centered at 800 nm. EL is due to radiative recombination of tunneling carriers in Si-nanocrystals(NC) with small contribution of oxide defects (peak at 650 nm). EL images reveal inhomogeneous emission structures on the micrometer scale. Mainly, a small number of bright spots with diffraction limited size (similar to 600 nm) with a homogeneous background are observed and their EL spectra measured using an imaging spectrometer with a liquid-nitrogen-cooled CCD camera. The bright EL spots originate from the efficiently excited emission of oxide defects and/or emission of a few (possibly single) Si-NC, most likely at places with locally increased current. The low efficiency is probably a consequence of current tunneling through optically inactive nanocrystals or defects in a very thin oxide layer.

  • 13. Wang, S.
    et al.
    Pasiskevicius, Valdas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    High-efficiency frequency converters with periodically-poled Rb-doped KTiOPO42007Inngår i: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 30, nr 4, s. 594-599Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Periodic structuring of ferroelectric domains in 2 mol% Rb-doped KTP is demonstrated using a room-temperature electric-field poling. Drastically reduced ionic conductivity in this material, or 2-orders of magnitude lower than in flux-grown KTP, makes it a good candidate for fabrication of quasi-phase-matched frequency converters. A coercive field of 3.4 kV/mm has been measured at room temperature. The dispersion of the index of refraction and effective nonlinearity in quasi-phase-matched structures in Rb-doped KTP did not show significant difference from KTP. A normalized conversion efficiency of 2.5% W-1 cm(-1) for the frequency-doubling of 908.4 nm has been obtained. A singly-resonant mid-infrared optical parametric oscillator with periodically-poled Rb-doped KTP generating 1.53 mu m signal and 3.49 mu m idler had threshold of 51 MW/cm(2) which is comparable to the best-quality periodically-poled KTP structures in the same optical cavity.

1 - 13 of 13
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