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  • 1.
    Anand, Srinivasan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Desieres, Y.
    KTH, School of Engineering Sciences (SCI), Applied Physics. CEA LETI MINATEC, Grenoble, France.
    Visser, D.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Chen, D-Y
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Optical Coatings and Films Based on Photonic Semiconductor Nanostructure Assemblies2017In: 2017 19TH INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS (ICTON), IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    Photonic semiconductor nanostructure assemblies offer unique possibilities for light manipulation as well as for tailoring light-matter interaction by appropriate choice of their geometrical and material properties. The material-structure combination offers a variety of options for wavelength specific applications, deriving from the electronic properties of semiconductors and optical properties of individual and assemblies of nanostructures (particles, disks, pillars/wires etc.). We present an overview of our research on optical coatings based on semiconductor nanostructure assemblies focusing on their optical properties, different fabrication technologies and selected application examples. Design and simulations of the optical coatings are performed by finite difference time domain calculations, and are used as a guideline for fabrication. We discuss different routes for fabrication of nanostructured optical films/coatings including directed assembly and patterning of nanoparticles from solution phase, solution synthesis, combination of dry etching and colloidal lithography, transfer printing, and generation of flexible polymer films with embedded nanostructures. The fabricated films are validated by optical measurements and some device specific properties such as omni-directional broad-band anti-reflection in solar cells and efficient light extraction in light emitting diodes are demonstrated.

  • 2.
    Chen, Shula
    et al.
    Linkoping Univ, Dept Phys Chem & Biol, SE-58183 Linkoping, Sweden..
    Huang, Yuqing
    Linkoping Univ, Dept Phys Chem & Biol, SE-58183 Linkoping, Sweden..
    Visser, Dennis
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Anand, Srinivasan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Buyanova, Irina A.
    Linkoping Univ, Dept Phys Chem & Biol, SE-58183 Linkoping, Sweden..
    Chen, Weimin M.
    Linkoping Univ, Dept Phys Chem & Biol, SE-58183 Linkoping, Sweden..
    Room-temperature polarized spin-photon interface based on a semiconductor nanodisk-in-nanopillar structure driven by few defects2018In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 9, article id 3575Article in journal (Refereed)
    Abstract [en]

    Owing to their superior optical properties, semiconductor nanopillars/nanowires in one-dimensional (1D) geometry are building blocks for nano-photonics. They also hold potential for efficient polarized spin-light conversion in future spin nano-photonics. Unfortunately, spin generation in 1D systems so far remains inefficient at room temperature. Here we propose an approach that can significantly enhance the radiative efficiency of the electrons with the desired spin while suppressing that with the unwanted spin, which simultaneously ensures strong spin and light polarization. We demonstrate high optical polarization of 20%, inferring high electron spin polarization up to 60% at room temperature in a 1D system based on a GaNAs nanodisk-in-GaAs nanopillar structure, facilitated by spin-dependent recombination via merely 2-3 defects in each nanodisk. Our approach points to a promising direction for realization of an interface for efficient spin-photon quantum information transfer at room temperature-a key element for future spin-photonic applications.

  • 3.
    De Luca, Eleonora
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Sanatinia, Reza
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Mensi, Mounir
    KTH, School of Information and Communication Technology (ICT).
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Swillo, Marcin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Modal phase matching in nanostructured zincblende semiconductors for second-harmonic generation2017In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2017Conference paper (Refereed)
    Abstract [en]

    Gallium phosphide nanowaveguide arrays, designed to fulfill the phase matching conditions and field-overlap, are characterized by second-harmonic generation. The bandwidth of 30nm with maximum conversion efficiency of 10-3 is measured for 150fs optical pulses.

  • 4.
    De Luca, Eleonora
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Visser, Dennis
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Anand, Srinivasan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Swillo, Marcin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Gallium Indium Phosphide Microstructures with Suppressed Photoluminescence for Applications in Nonlinear Optics2019In: Optics Letters, ISSN 0146-9592, Vol. 44, no 21Article in journal (Refereed)
    Abstract [en]

    Gallium indium phosphide (Ga0.51In0.49P), lattice matched to gallium arsenide, shows remarkable second-order nonlinear properties, as well as strong photoluminescence due to its direct band gap. By measuring the second-harmonic generation from the GaInP microwaveguide (0.2 x 11 x 1300 μm) before and after stimulating intrinsic photobleaching, we demonstrate that the photoluminescence could be strongly suppressed (-34 dB), leaving the nonlinear properties unchanged, making it suitable for low-noise applications.

  • 5.
    De Luca, Eleonora
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Visser, Dennis
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Anand, Srinivasan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Swillo, Marcin
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Gallium indium phosphide nanostructures with suppressed photoluminescence for applications in nonlinear optics2018In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2018Conference paper (Refereed)
    Abstract [en]

    Nanostructured GaInP shows remarkable second-order nonlinear properties. By measuring the second harmonic generation before and after stimulating intrinsic photobleaching, we observed suppressed photoluminescence and unchanged nonlinear properties, making it suitable for low-noise applications. 

  • 6.
    Desieres, Yohan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Chen, Ding Yuan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Visser, Dennis
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Schippers, Casper
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Anand, Srinivasan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Strong light extraction enhancement using TiO2 nanoparticles-based microcone arrays embossed on III-Nitride light emitting diodes2018In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 112, no 23, article id 231101Article in journal (Refereed)
    Abstract [en]

    Colloidal TiO2 nanoparticles were used for embossing of composite microcone arrays on III-Nitride vertical-thin-film blue light emitting diodes (LEDs) as well as on silicon, glass, gallium arsenide, and gallium nitride surfaces. Ray tracing simulations were performed to optimize the design of microcones for light extraction and to explain the experimental results. An optical power enhancement of similar to 2.08 was measured on III-Nitride blue LEDs embossed with a hexagonal array of TiO2 microcones of similar to 1.35 mu m in height and similar to 2.6 mu m in base width, without epoxy encapsulation. A voltage increase in similar to 70mV at an operating current density of similar to 35 A/cm(2) was measured for the embossed LEDs. The TiO2 microcone arrays were embossed on functioning LEDs, using low pressures (similar to 100 g/cm(2)) and temperatures <= 100 degrees C. 

  • 7.
    Dev Choudhury, Bikash
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Semiconductor Materials, HMA.
    Anand, Srinivasan
    Rapid thermal annealing treated spin-on doped antireflective radial junction Si nanopillar solar cell2017In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 25, no 8, p. A200-A207Article in journal (Refereed)
    Abstract [en]

    Radial junction nanopillar Si solar cells are interesting for cost effective efficiency improvement. Here, we address a convenient top-down fabrication of Si nanopillar solar cells using spin-on doping and rapid thermal annealing (RTA) for conformal PN junction formation. Broadband suppressed reflection as low as an average of 5% in the 300-1100 nm wavelength range and un-optimized cell efficiency of 7.3% are achieved. The solar cell performance can be improved by optimization of spin-on-doping and suitable surface passivation. Overall, the all RTA processed, spin-on doped nanopillar radial junction solar cell shows a very promising route for low cost and high efficiency thin film solar cell perspectives.

  • 8.
    Désières, Yohan
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Chen, Dingyuan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Visser, Dennis
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Schippers, Casper
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Vaufrey, D.
    Demars, P.
    Levy, F.
    Largeron, C.
    Lalauze, Q.
    Anand, Srinivasan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Nanoparticle-based microstructures for light extraction enhancement in nitride-based LEDs2018In: Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XXII, SPIE - International Society for Optical Engineering, 2018, article id 105540QConference paper (Refereed)
    Abstract [en]

    TiO2 nanoparticles dispersion was used to fabricate three dimensional (3D) composite structures on the surface of various substrate materials as well as on the surface of nitride light emitting diodes (LEDs). Optical power enhancements in the range of ∼1.4-2.1 were measured.

  • 9.
    Johansson, Wilhelm
    et al.
    Linnaeus Univ, Fac Technol, Dept Built Environm & Energy Technol, LNU Glass Grp, Vaxjo, Sweden..
    Peralta, Albert
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum and Biophotonics.
    Jonson, Bo
    Linnaeus Univ, Fac Technol, Dept Built Environm & Energy Technol, LNU Glass Grp, Vaxjo, Sweden..
    Anand, Srinivasan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Österlund, Lars
    Uppsala Univ, Dept Engn Sci, Angstrom Lab, Uppsala, Sweden..
    Karlsson, Stefan
    RISE Res Inst Sweden, Built Environm Div, RISE Glass, Vaxjo, Sweden..
    Transparent TiO2 and ZnO Thin Films on Glass for UV Protection of PV Modules2019In: FRONTIERS IN MATERIALS, ISSN 2296-8016, Vol. 6, article id 259Article in journal (Refereed)
    Abstract [en]

    Failure of PV modules frequently occurs as a result of degradation of their encapsulation material by destructive UV radiation. Both the life expectancy and efficiency of PV modules can be improved by reducing the transmittance of the destructive UV radiation through the cover glass without compromising the transmittance in the visible wavelength region. In addition, if the absorbed UV photons can be down-shifted to wavelengths that can be more efficiently converted to electrical energy, an additional increase of the PV efficiency could be achieved. In this study we have investigated transparent ZnO and TiO2 thin films deposited by spray pyrolysis on soda lime silicate float glass as functional layers on PV cover glass. The optical bandgap, UV-cutoff, UV-Vis transmittance, reflectivity (total and diffuse) and photoluminescence have been determined. The ZnO coating shifted the optical bandgap to longer wavelengths, resulting in a reduction of the transmittance of destructive UV radiation by up to similar to 85%. Distinct photoluminescence peaks at 377 nm and at 640 nm were observed for one of the ZnO samples. The TiO2 coated glasses also showed an increased UV cutoff, which resulted in a reduction of transmittance of destructive UV radiation by up to 75%. However, no photoluminescence peaks could be observed from the TiO2 films with 325 nm excitation laser, which can be explained by the fact that only indirect interband transitions are accessible at this excitation wavelength. Deposition of both ZnO and TiO2 coatings resulted in a reduction of the transmitted light convertible by PV modules, by up to 12.3 and 21.8%, respectively. The implication of the results is discussed in terms of lifetime expectancy and efficiency of PV modules.

  • 10.
    Maknys, Kestutis
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Douhéret, Olivier
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Electrical characterization of InGaAs/InP quantum wells by scanning capacitance microscopy2018In: Microscopy of Semiconducting Materials 2003, CRC Press, 2018, p. 645-648Chapter in book (Refereed)
    Abstract [en]

    In this work, cross-sectional scanning capacitance microscopy (SCM) is used to investigate 5, 10, and 20 nm InGaAs/InP (lattice matched) quantum wells grown by metalorganic vapour phase epitaxy and sandwiched between Si-doped InP barriers. It is demonstrated that SCM is capable of detecting the electrons accumulated in the quantum wells and that the SCM signal shows a systematic trend for the wells of different width. It is also shown that at appropriate tip-sample DC biases depletion regions in the barriers adjacent to the wells are clearly resolved.

  • 11.
    Ravishankar, Ajith P.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    van Tilburg, Marvin A.
    KTH, School of Engineering Sciences (SCI), Applied Physics. Eindhoven Univ Technol, Dept Appl Phys, NL-5600 MB Eindhoven, Netherlands..
    Vennberg, Felix
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Visser, Dennis
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Anand, Srinivasan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Color generation from self-organized metato-dielectric nanopillar arrays2019In: NANOPHOTONICS, ISSN 2192-8606, Vol. 8, no 10, p. 1771-1781Article in journal (Refereed)
    Abstract [en]

    Nanostructures composed of dielectric, metallic or metalo-dielectric structures are receiving significant attention due to their unique capabilities to manipulate light for a wide range of functions such as spectral colors, anti-reflection and enhanced light-matter interaction. The optical properties of such nanostructures are determined not only by the shape and dimensions of the structures but also by their spatial arrangement. Here, we demonstrate the generation of vivid colors from nanostructures composed of spatially disordered metalo-dielectric (In/InP) nanopillar arrays. The nanopillars are formed by a singlestep, ion-sputtering-assisted, self-assembly process that is inherently scalable and avoids complex patterning and deposition procedures. The In/InP nanopillar dimensions can be changed in a controlled manner by varying the sputter duration, resulting in reflective colors from pale blue to dark red. The fast Fourier transform (FFT) analysis of the distribution of the formed nanopillars shows that they are spatially disordered. The electromagnetic simulations combined with the optical measurements show that the reflectance spectra are strongly influenced by the pillar dimensions. While the specular and diffuse reflectance components are appreciable in all the nanopillar samples, the specular part dominates for the shorter nanopillars, thereby leading to a glossy effect. The simulation results show that the characteristic features in the observed specular and diffused reflectance spectra are determined by the modal and light-scattering properties of single pillars. While the work focuses on the In/InP system, the findings are relevant in a wider context of structural color generation from other types of metalo-dielectric nanopillar arrays.

  • 12. Sahoo, Pankaj K.
    et al.
    Choudhury, Bikash Dev
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Joseph, Joby
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    ZnO nanowire-enabled light funneling effect for antireflection and light convergence applications2017In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 42, no 1, p. 45-48Article in journal (Refereed)
    Abstract [en]

    We present a new light trapping technique to reduce reflection loss, as well as for light, focusing at submicron scales for solar cell and image sensing applications. We have fabricated hexagonal arrays of ZnO funnel-like structures on Si substrate by the patterned growth of ZnO nanowires in a hydrothermal growth process. The funnels are optimized so that the effective refractive index along the vertical direction decreases gradually from the Si surface to the top of funnel to reduce Fresnel reflection at a device-air interface. Finite difference time domain simulation is used for optimization of the minimum reflectivity and to analyze optical properties such as angle dependency, polarization dependency, and funneling effect. The structures function similar to a GRIN lens in light trapping and convergence. An optimized structure reduces the average reflectivity close to 3% in the wavelength range of 300-1200 nm with the possibility of confining incident light to a few hundreds of nano-meters.

  • 13.
    Visser, Dennis
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Basuvalingam, Saravana Balaji
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Desieres, Yohan
    KTH, School of Engineering Sciences (SCI), Applied Physics. University Grenoble Alpes, CEA, LETI, MINATEC Campus, Grenoble, F-38054, France.
    Anand, Srinivasan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Optical properties and fabrication of dielectric metasurfaces based on amorphous silicon nanodisk arrays2019In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 27, no 4, p. 5353-5367Article in journal (Refereed)
    Abstract [en]

    Dielectric metasurfaces based on amorphous silicon (a-Si) nanodisks are interesting for nanophotonic applications due to the high refractive index and mature/low temperature fabrication of a-Si. The investigated metasurfaces consist of a-Si nanodisk arrays embedded in a transparent film. The diameter-dependent optical properties of the nanodisk Mie resonators have been investigated by finite-difference time-domain (FDTD) simulations and spectrally-resolved reflectivity and transmission measurements. Well-ordered substrate-free a-Si nanodisk arrays were fabricated and characterized with regard to their broadband anti-reflection properties when placed on a crystalline silicon (c-Si) surface, and reflectivity/ transmission properties when embedded in a polydimethylsiloxane (PDMS) film. Our results confirm broadband anti-reflection when placed on silicon, while the optical characteristics of the nanodisks embedded in PDMS are shown to be potentially useful for color/NIR filter applications as well as for coloring on the micro/nanoscale. under the terms of the OSA Open Access Publishing Agreement

  • 14.
    Visser, Dennis
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Jaramillo Fernandez, Juliana
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Haddad, Gabriel
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Sotomayor Torres, Clivia M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Anand, Srinivasan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Ion bombardment induced formation of self-organized wafer-scale GaInP nanopillar assemblies2020In: Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics, ISSN 2166-2746, E-ISSN 2166-2754, Vol. 38, no 1, article id 012801Article in journal (Refereed)
    Abstract [en]

    Ion sputtering assisted formation of nanopillars is demonstrated as a wafer-scale, lithography-free fabrication method to obtain high optical quality gallium indium phosphide (GaInP) nanopillars. Compared to binary materials, little has been reported on the formation of self-organized ternary nanostructures. Epitaxial (100) Ga0.51In0.49P layers lattice matched to GaAs were sputtered by nitrogen (N2) ions with relatively low ion beam energies (∼400 eV) to reduce ion bombardment induced damage. The influence of process parameters such as temperature, sputter duration, ion beam energy, and ion beam incidence angle on the pillar formation is investigated. The fabricated GaInP nanopillars have average diameters of ∼75-100 nm, height of ∼220 nm, and average density of ∼2-4 × 108 pillars/cm2. The authors show that the ion beam incidence angle plays an important role in pillar formation and can be used to tune the pillar shape, diameter, and spatial density. Specifically, tapered to near cylindrical pillar profiles together with a reduction in their average diameters are obtained by varying the ion beam incidence angle from 0° to 20°. A tentative model for the GaInP nanopillar formation is proposed based on transmission electron microscopy and chemical mapping analysis. μ-Photoluminescence and μ-Raman measurements indicate a high optical quality of the c-GaInP nanopillars.

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