Author Affiliations
Abstract
1 Key Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
2 School of Physics and Optoelectronics, South China University of Technology, Guangzhou 510640, China
We investigate the dynamic crystallization processes of colloidal photonic crystals, which are potentially invaluable for solving a number of existing and emerging technical problems in regards to controlled fabrication of crystals, such as size normalization, stability improvement, and acceleration of synthesis. In this paper, we report systematic high-resolution optical observation of the spontaneous crystallization of monodisperse polystyrene (PS) micro-spheres in aqueous solution into close-packed arrays in a static line optical tweezers. The experiments demonstrate that the crystal structure is mainly affected by the minimum potential energy of the system; however, the crystallization dynamics could be affected by various mechanical, physical, and geometric factors. The complicated dynamic transformation process from 1D crystallization to 2D crystallization and the creation and annihilation of dislocations and defects via crystal relaxation are clearly illustrated. Two major crystal growth modes, the epitaxy growth pattern and the inserted growth pattern, have been identified to play a key role in shaping the dynamics of the 1D and 2D crystallization process. These observations offer invaluable insights for in-depth research about colloidal crystal crystallization.
Photonic crystals Optical confinement and manipulation Photonics Research
2017, 5(3): 03000201
Author Affiliations
Abstract
Institute of Electrical and Information Engineering, Christian-Albrechts-Universit?t zu Kiel,Kaiserstr. 2, D-24143 Kiel, Germany
Photonic crystal slabs integrated into organic light-emitting diodes (OLEDs) allow for the extraction of waveguide modes and thus an increase in OLED efficiency. We fabricated linear Bragg gratings with a 460-nm period on flexible polycarbonate substrates using UV nanoimprint lithography. A hybrid organic–inorganic nanoimprint resist is used that serves also as a high refractive index layer. OLEDs composed of a poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) polymer anode, an organic emission layer [poly(p-phenylene vinylene) (PPV)-derivative “Super Yellow”], and a metal cathode (LiF/Al) are deposited onto the flexible grating substrates. The effects of photonic crystal slab deformation in a flexible OLED are studied in theory and experiment. The substrate deformation is modeled using the finite-element method. The influence of the change in the grating period and the waveguide thickness under bending are investigated. The change in the grating period is found to be the dominant effect. At an emission angle of 20° a change in the resonance wavelength of 1.2% is predicted for a strain of 1.3% perpendicular to the grating grooves. This value is verified experimentally by analyzing electroluminescence and photoluminescence properties of the fabricated grating OLEDs.
Gratings Gratings Photonic crystals Photonic crystals Light-emitting diodes Light-emitting diodes Organic materials Organic materials Polymers Polymers Photoluminescence Photoluminescence Photonics Research
2015, 3(2): 02000032
Author Affiliations
Abstract
1 Hubei Key Laboratory of Intelligent Wireless Communications, College of Electronics and Information Engineering, South-central University for Nationalities, Wuhan, Hubei 430074, China
2 Wuhan National Laboratory for Optoelectronics (WNLO), School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
Wepresent a novel method for engineering ultra-flattened-dispersion photonic crystal fibers with uniform air holes by rotations of inner air-hole rings around the fiber core. By choosing suitable rotation angles of each inner ring, theoretical results show that normal, anomalous, and nearly zero ultra-flattened-dispersion fibers in wide spectra ranges of interest can be obtained alternatively. Moreover, in our dispersion sensitive analysis, these types of fibers are robust to variations from optimal design parameters. The method is suitable for the accurate adjustment of fiber dispersion within a small range, which would be valuable for the fabrication of ultra-flattened-dispersion fibers and also have potential applications in wide-band high-speed optical communication systems.
Photonic crystal fibers Fiber properties Fiber design and fabrication Photonics Research
2014, 2(2): 02000059
