Tailored disorder - an advanced materials design for innovative photonic applications
Disorder, complex order, and broken periodicity are an emerging and lively research area in photonic materials, whose optical response fundamentally relies on the structural architecture. Materials that are not periodically ordered reveal novel and designable manipulation of light. Numerous important scientific achievements are reported in the areas of biology, materials science, and nano-photonics and define routes to a new design guide for innovative materials with advanced optical properties.
Natural systems are able to produce materials surfaces with unique properties. The formation of complex three-dimensional structures in nature is of fundamental importance to break the limits imposed by available construction elements. Structuring into ordered, and especially into complex or disordered systems is the key to define new roadmaps to innovative materials engineering. The importance of disordered structures in biology can be most efficiently demonstrated on natural optical materials. It has been shown that structural disorder is most beneficial in nature and can be used as an engineering guide for the development of novel advanced photonic devices. While still in its infancy, the general subject of structural disorder is rapidly emerging into an area of interdisciplinary scientific interest. Therefore, the purpose of this symposium is to bring together specialists from various scientific communities such as physics, biology and materials science and engineering to advance the structural disorder research area based on basic and applied research with emphasis on multidisciplinary approaches and fabrication routes. Contributions from the fields of theoretical, applied and computational physics, optics and photonics in biology, materials engineering and nano-patterning are encouraged. The development of novel approaches and design routes to realize tailored disorder in materials will be one of the main topics of the symposium. Presentations not limited to various patterning procedures such as self-assembly, sol-gel procedures, solid state synthesis, soft lithography, layer-by-layer deposition with the focus on materials functions and properties are welcome.
Hot topics to be covered by the symposium:
- Advanced optics;
- Disorder in optics;
- Anderson localization of light;
- Random lasing;
- Structural optics;
- Biological optical materials;
- Bioinspired optical materials;
- Cavity quantum electrodynamics (cQED);
- Solid-state lighting, security and (quantum) authentication;
- Ultrafast all-optical switching;
- Wavefront shaping.
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SESSION 1 : .
Authors : Lukas Maiwald, D. Jalas, A. Yu. Petrov, M. Eich
Affiliations : Hamburg University of Technology, Institute of Optical and Electronic Materials, Eißendorferstr. 38, 21073 Hamburg, Germany
Resume : Structural coloration offers great possibilities for extremely light-fast colors based on simple and environmentally friendly material compositions. Highly saturated, non-iridescent blue and green structural colors are found in nature and have also been shown experimentally. Such disordered structures reflect short wavelengths and transmit long wavelengths. However, producing non-iridescent red structural colors with the same structures is problematic as long wavelengths should be reflected and short wavelengths transmitted in this case. Disordered structures with non-iridescent structural colors have been shown to feature spherically shaped Fourier transforms. We simulated a structure producing an ideally spherical Fourier transform to gain deeper insight into the mechanisms behind structural coloration. Using the Ewald sphere approach we propose a simple method to predict the reflection from structures with low refractive index contrasts. We found that, due to the wavelength dependent scattering directions predicted by the Ewald sphere approach, Fresnel reflection at the inner surface of the structure can lead to a distinct reflection peak even at longer wavelengths. When the refractive index contrast increases, diffuse reflection, being more pronounced for short wavelengths, overshadows the peak reflection and leads to limited color purity. We show for shorter wavelengths that inner reflections also lead to longer photon traveling times inside the structure. This leads to a conclusive explanation of the known improvement of color saturation by addition of broadband absorbers.
Authors : José M. Miranda-Munoz, Sol Carretero-Palacios, Alberto Jimenez-Solano, Yuelong Li, Gabriel Lozano, and Hernan Míguez
Affiliations : Institute of Materials Science of Seville, Spanish National Research Council-Unviersity of Seville, Av. Americo Vespucio 49, 41092, Seville, Spain
Resume : Herein, an optically disordered material is developed to enhance the performance of dye-sensitized solar cells (DSSCs) that operate under bifacial conditions. Spherical submicron TiO2 particles are randomly dispersed in a mesoporous TiO2 matrix by solution processing in a fast and inexpensive way. A Monte Carlo approach is used to calculate the trajectory of individual photons impinging the cell. Moreover, our model makes use of Fresnel coefficients at the interface of each two layers, and Mie theory to account for the scattering efficiency and the angular distribution of the light scattered by every TiO2 sphere. We demonstrate that a careful choice of the size of the TiO2 inclusions within the photoanode together with the appropriate particle number density enable optimized DSSCs. Power conversion efficiency enhancements as high as 25% and 33% are attained for devices operating under front and rear illumination, respectively, compared to an 8-µm thick standard DSSC. Indeed, the random nature of our approximation leads to solar cells with remarkable bifacial character, as proven by the high 80% rear/front efficiency ratio attained, which is among the largest reported for this sort of devices. Our approach may be also applied to the development of other optoelectronic devices for which an accurate control of light absorption and emission is desired. References - F. E. Gálvez, P. R. F. Barnes, J. Halme, and H. Míguez, ?Dye sensitized solar cells as optically random photovoltaic media?, Energy Environ. Sci. 7, 689 (2014). - J. M. Miranda-Muñoz, S. Carretero-Palacios, A. Jiménez-Solano, Y. Li, G. Lozano and H. Míguez, ?Efficient bifacial dye-sensitized solar cells through disorder by design?, J. Mater. Chem. A, DOI: 10.1039/c5ta10091g.
Authors : S. Venkatachalam1, F. Vaurette1, G. Ducournau1, J. F. Lampin1, D. Hourlier1,*
Affiliations : 1IEMN, UMR-8520, Avenue Poincaré, BP 69, 59652 Villeneuve d'Ascq, France *firstname.lastname@example.org
Resume : Turbostratic carbon consists mainly of polyaromatic carbon with or without heteroatoms (N, H, O). Its structure is made of stacked graphene layers in parallel array but without any three dimensional order, as in graphite structure. Such disordered graphitic microstructure is produced very simply, by heating organic polymers in inert atmosphere. This work discusses about the thermal conversion of a commercially available organic polymer, Kapton® HN polyimide, and the interaction of terahertz radiation on various carbon-microstructures. The progress of carbonization was followed by a variety of analytical methods including thermogravimetry coupled with mass spectrometry, Infra-red and Raman spectroscopies. Raman spectra acquired from the carbonaceous residues exhibited the two characteristic bands, D (1358 cm-1) and G (1593 cm-1), indicating the formation of turbostratic carbon. The electrical conductivity progressively increases with the heat treatment temperature from 2×10-3 S cm-1 at 700 °C to 298 S cm-1 > 900 °C. Moreover, the heat-treated materials show variant degrees of transmission and reflection in the frequency range 220-500 GHz. The thickness of the material, as well as the structural rearrangement of carbon can cause significant deviations in how a sub-millimetric wave is transmitted, and reflected, leading to different absorptions. The maximal absorption of 47% was obtained with the carbonaceous residue obtained between 750-800 °C.
SESSION 2 : .
Authors : K. Kertesz1, G. Piszter1, Zs. Balint2, L. P. Biro1
Affiliations : 1: Institute of Technical Physics and Materials Science, Centre for Energy Research, 1525 Budapest, PO Box 49, Hungary (http://www.nanotechnology.hu/); 2: Hungarian Natural History Museum, Baross utca 13, H-1088 Budapest, Hungary
Resume : In butterflies, coloration is often achieved by nanoarchitectures generating structural color. In their case a chitinous layer forms a complex nanocomposite, the periodicity of which fits in the range of the visible light wavelength. A characteristic reflection develops providing the various structural colors of butterflies . Both sides of the wings are covered by scales which may exhibit a large variety of photonic nanostructures . Blue polyommatus butterflies in this study possess a short range ordered structure called pepper-pot type structure. We demonstrated on closely related species living in the same habitat the unambiguous connection between the scale nanostructure variations and the color . Recently we investigated the variability of the color of P. icarus males living in the same location. We found for 100 samples that the variation in the spectral position of the reflectance maximum is smaller than +/-40 nm. We investigated for the first time a large set (2824 data points) of specimens collected over a wide geographical area: the palearctic ecozone (west to east: Western Europe to Eastern Asia; north to south: Finland to Afganistan). The spectral position of the reflectance maxima was found to have the same variation of the order of +/- 40 nm, but clear geographical particularities were evidenced.  LP Biró & JP Vigneron, Laser & Photonics Rev. 5 (2011) 27  H. Ghiradella, Appl. Opt. 30 (1991) 3492  Zs. Bálint et al. JRS Interface 73 (2012) 1745
Authors : Aisling Kerr; Nebras Al-Attar; James Rice
Affiliations : School of Physics, UCD
Resume : The transmission of light through a fibre plays an important role in many optical devices and techniques such as optical communication, medical light sensing and fibre optical sensing. Microscale optical waveguides are crucial for steering and manipulating light in such devices. Organic materials are easily processed into a variety of nano and microshapes cost effectively and efficiently depending on the solution in which they are dissolved and nature of their polarity making them attractive for opto-electronics. We study self-assembled hollow microtubes formed from an organic molecule (nile red). These microtubes were seen to passively waveguide light when probed at a higher wavelength relative to their absorption band threshold. The input light directly propagated through the other end of the tube creating Fabry-Perot fringing in the observed waveguide light. Studies of microtube interactions/junctions were also performed and compared to isolated microstructures. Active waveguiding was also observed when probing within the absorption band of the microtube. The emitted light from the ends of tubes were spectrally shifted relative to the emission wavelengths of the starting material which is indicative of active waveguiding.
Authors : Rusul M. Al-Shammari1, Michele Manzo2, Katia Gallo2, James H. Rice1, and Brian J. Rodriguez1,3.
Affiliations : 1School of Physics, University College Dublin, Belfield, Dublin 4, Ireland; 2Department of Applied Physics, KTH ? Royal Institute of Technology, 106 91 Stockholm, Sweden; 3Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland.
Resume : Optofluidic materials are of interest in a variety of device applications, particularly in bio-system-on-a-chip devices. An important aspect of optimising these materials for such devices is the ability to engineer materials properties, e.g., structure and charge, which allow the contact angle (CA) to be tuned. Using biocompatibile ferroelectric lithium niobate (LN), which is well known for various nonlinear optical applications, it is shown that the CA can be tuned via ferroelectric domain and polarization engineering and subsequent polarization directed photo-assisted deposition of metallic nanostructures. The LN templates have been patterned via electric field poling to create periodically poled (PP) LN or using a periodic proton exchange (PPE) chemical patterning process to create PPELN. PPLN samples present an optically flat surface with charge-patterned regions that can be preferentially etched to create structured, three dimensional surfaces. PPELN surfaces have patterned surface chemistry and topographical features associated with the fabrication processing, e.g., swelling during proton exchange and over-etching during masking. The chemical patterning provides the ability to tailor the electrostatic fields at the surface, which can be used to fabricate microscale arrays of metallic nanostructures. By combining patterned LN surfaces and metal deposition, it is shown that the CA of LN can be reproducibly tailored between 41.40 ± 0.05° and 106.40 ± 0.67°.
Authors : Lagutin Andrei
Affiliations : Belarusian State Academy of Telecommunications
Resume : A study of bend-induced losses in a silica-based single-mode microstructured fiber G.652 has been conducted. With the use of the equivalent step-index profile method in approximation of waveguide parameters of microstructured fiber (normalized frequency and normalized transverse attenuation constant) the effect of bending on the spectral position of the fundamental mode short-wavelength leakage boundary has been analyzed. Upon measurement of spectral characteristics of attenuation in the considered fibers good accordance of numerical and experimental data has been found out. It is shown that increase of the air content in the holey cladding leads to expansion of the mentioned boundary to lower wavelengths for the value from 150 to 800 nm depending on the core size and bending conditions. A single-transverse-mode propagation is achieved on fiber length of 5-10 meters due to a substantial difference in losses of fundamental and higher-order guided modes attained by bending. Optical losses in all studied samples are less than 10 dB/km at the wavelength λ = 1550 nm.
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