scholarly journals Study on the Photonic Band Gaps of the Face Centered Cubic Crystals

2016 ◽  
Vol 70 ◽  
pp. 63-75
Author(s):  
K.B.S.K.B. Jayawardana ◽  
K.A.I.L. Wijewardena Gamalath
Keyword(s):  
Photonic Crystals ◽  
Band Gap ◽  
Filling Factor ◽  
Dielectric Material ◽  
Dielectric Materials ◽  
Face Centered Cubic ◽  
Gap Ratio ◽  
Dielectric Contrast ◽  
Dielectric Spheres ◽  
Face Centered

Since the dielectric contrast of photonic crystals play an important role in determining the existence of a photonic gap, the photonic energy bands, density of states of face centered cubic structured photonic crystals formed from spheres of several dielectric materials placed in air were calculated using the plane wave expansion method. A complete band gap was obtained between second and third bands with a gap to mid gap frequency ratio in the range for the dielectric contrast in the range 11-16 with dielectric spheres of radius with a filling factor of 0.134 and fordielectric contrast of 200 with . A complete gap was not found for the dielectric contrast of 3.9. A complete band gap can be obtained for filling factors for the dielectric contrast in the range with an optimum band gap for the filling factor 0.134 while GaAs () has almost a constant optimum band gap in this range. The largest gap to mid gap ratio of was obtained for GaP (). For dielectric spheres of and larger gap to mid gap ratio were obtained for the dielectric contrast while the largest were obtained for . The only dielectric material BaSrTiO3 () which gives a band gap for the filling factor of 0.4524 can be used in microwave applications.

THE SIZE INFLUENCE OF SILICA MICROSPHERES ON PHOTONIC BAND GAP OF PHOTONIC CRYSTALS

2007 ◽  
Vol 21 (16) ◽  
pp. 2761-2768 ◽  
Author(s):  
XIYING MA ◽  
ZHIJUN YAN
Keyword(s):  
Photonic Crystals ◽  
Band Gap ◽  
Photonic Band Gap ◽  
Three Dimensional ◽  
Refraction Index ◽  
Face Centered Cubic ◽  
Silica Microspheres ◽  
Large Shift ◽  
Face Centered ◽  
Photonic Band

The size influence of silica microspheres on the photonic band gap (PBG) of three-dimensional face-centered-cubic (fcc) photonic crystals (PCs) is studied by means of colloidal photonic crystals, which are self-assembled by the vertical deposition technique. Monodispersed SiO 2 microspheres with a diameter of 220–320 nm are synthesized using tetraethylorthosilicate (TEOS) as a precursor material. We find that the PBG of the PCs shifts from 450 nm to 680 nm with silica spheres increasing from 220 to 320 nm. In addition, the PBG moves to higher photon energy when the samples are annealed in a temperature range of 200–700°C. The large shift results from the decrease in refraction index of silica due to moisture evaporation.

scholarly journals Body Centered Photonic Crystal

2016 ◽  
Vol 66 ◽  
pp. 96-108 ◽  
Author(s):  
K.B.S.K.B. Jayawardana ◽  
K.A.I.L. Wijewardena Gamalath
Keyword(s):  
Band Gap ◽  
Filling Factor ◽  
Energy Gap ◽  
Dielectric Material ◽  
Expansion Method ◽  
Energy Bands ◽  
Lattice Constants ◽  
Dielectric Spheres ◽  
Frequency Ratios ◽  
Gap Width

The photonic energy bands of body centered cubic photonic crystals formed from SiO2, GaP, Si, InAs, GaAs, InP, Ge and BaSrTiO3 dielectric spheres drilled in air and air holes drilled in these dielectric mediums were calculated using the plane wave expansion method. The filling factor for each dielectric material was changed until a complete energy gap was obtained and then the density of states was calculated. There were no complete band gaps for air spheres drilled in these eight dielectric mediums. The lattice constants were determined by using wavelengths in the region . The variation of the band gap widths with the filling factor and the variation of gap width to midgap frequency ratios with dielectric contrast were investigated. The largest band gap width of 0.021 for normalized frequency was obtained for GaP for the filling factor of 0.0736. The mode filed distributions were obtained by guiding a telecommunication wave with wavelength through a photonic cell formed from GaP spheres in air with a filling factor of 0.0736 for transverse electric and magnetic modes.

scholarly journals Enhanced sunlight photocatalytic activity and biosafety of marine-driven synthesized cerium oxide nanoparticles

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Somayeh Safat ◽  
Foad Buazar ◽  
Salim Albukhaty ◽  
Soheila Matroodi
Keyword(s):  
Photocatalytic Activity ◽  
Band Gap ◽  
Color Change ◽  
Removal Rate ◽  
Average Crystallite Size ◽  
Face Centered Cubic ◽  
One Pot ◽  
Stabilizing Agents ◽  
Face Centered ◽  
Living Organisms

AbstractThis contribution presents the biosynthesis, physiochemical properties, toxicity and photocatalytic activity of biogenic CeO2 NPs using, for the first time, marine oyster extract as an effective and rich source of bioreducing and capping/stabilizing agents in a one-pot recipe. CeO2 NPs formation was initially confirmed through the color change from light green to pale yellow and subsequently, their corresponding absorption peak was spectroscopically determined at 310 nm with an optical band-gap of 4.67 eV using the DR-UV technique. Further, XRD and Raman analyses indicated that nanoceria possessed face-centered cubic arrangements without any impurities, having an average crystallite size of 10 nm. TEM and SEM results revealed that biogenic CeO2 NPs was approximately spherical in shape with a median particle size of 15 ± 1 nm. The presence of various bioorganic substances on the surface of nanoparticles was deduced by FTIR and TGA results. It is found that marine-based nanoceria shows no cytotoxic effect on the normal cell, thus indicating their enhanced biocompatibility and biosafety to living organisms. Environmentally, due to energy band gap, visible light-activated CeO2 nanocatalyst revealed superior photocatalytic performance on degradation of methylene blue pollutant with removal rate of 99%. Owing to the simplicity, cost-effectiveness, and environmentally friendly nature, this novel marine biosynthetic route paves the way for prospective applications of nanoparticles in various areas.

Photonic band gap in the face-centered cubic lattice of spherical shells connected by cylindrical tubes

2005 ◽  
Vol 72 (11) ◽  
Author(s):  
Hong-Bo Chen ◽  
Yong-Zheng Zhu ◽  
Yan-Ling Cao ◽  
Yan-Ping Wang ◽  
Yuan-Bin Chi
Keyword(s):  
Band Gap ◽  
Photonic Band Gap ◽  
Face Centered Cubic ◽  
Spherical Shells ◽  
Cubic Lattice ◽  
Cylindrical Tubes ◽  
The Face ◽  
Face Centered ◽  
Photonic Band

Characteristic band gap structures of high dielectric contrast photonic crystals

2011 ◽  
Vol 1343 ◽  
Author(s):  
Sheng D. Chao ◽  
Hsin Y. Peng
Keyword(s):  
Photonic Crystals ◽  
Band Gap ◽  
Hexagonal Lattice ◽  
Dispersion Curves ◽  
Band Gaps ◽  
Circular Cylinders ◽  
Change Characteristics ◽  
Dielectric Contrast ◽  
Full Band ◽  
High Dielectric

ABSTRACTConventional photonic crystals exhibit low-lying full band gaps for the dielectric contrast smaller than 15. As the dielectric contrast increases, the band gap patterns change characteristics and exhibit interesting properties. In particular, the dispersion curves near the band gap region become concentrated to the middle band frequencies and exhibit an overall red shift in frequency. For a dielectric column photonic crystal made of a hexagonal lattice of circular cylinders, the maximum full band gap was found at the dielectric contrast as high as 27.5, which is attainable by using ceramics materials. The gap opens at high-lying bands, has simultaneous TM and TE band edges, and exhibit flattened dispersion curves near the band edges.

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