Browsing by Subject "Germanium compounds"
Now showing 1 - 5 of 5
Results Per Page
Sort Options
Item Open Access Characterization of thermally poled germanosilicate thin films(Optical Society of American (OSA), 2004) Ozean, A.; Digonnet, M.J.F.; Kino G.S.; Ay F.; Aydınlı, AtillaWe report measurements of the nonlinearity profile of thermally poled low-loss germanosilicate films deposited on fused-silica substrates by PECVD, of interest as potential electro-optic devices. The profiles of films grown and poled under various conditions all exhibit a sharp peak ∼0.5 μm beneath the anode surface, followed by a weaker pedestal of approximately constant amplitude down to a depth of 13-16 μm, without the sign reversal typical of poled undoped fused silica. These features suggest that during poling, the films significantly slow down the injection of positive ions into the structure. After local optimization, we demonstrate a record peak nonlinear coefficient of ∼1.6 pm/V, approximately twice as strong as the highest reliable value reported in thermally poled fused silica glass, a significant improvement that was qualitatively expected from the presence of Ge. ©2004 Optical Society of America.Item Open Access Infrared absorption spectroscopy of monolayers with thin film interference coatings(Optical Society of America, 2017) Ayas, Sencer; Bakan, Gökhan; Ozgur, E.; Celebi, Kemal; Dana, AykutluWe report high performance Infrared spectroscopy platforms based on interference coatings on metal using CaF2 dielectric films and Ge2Sb2Te5 (GST) phase-change films. IR vibrational bands of proteins and organic monolayers are also detected.Item Open Access Plasma enhanced chemical vapor deposition of low-loss as-grown germanosilicate layers for optical waveguides(SPIE, 2004) Ay, Feridun; Agan, S.; Aydınlı, AtillaWe report on systematic growth and characterization of low-loss germanosilicate layers for use in optical waveguides. Plasma enhanced chemical vapor deposition (PECVD) technique was used to grow the films using silane, germane and nitrous oxide as precursor gases. Chemical composition was monitored by Fourier transform infrared (FTIR) spectroscopy. N-H bond concentration of the films decreased from 0.43 ×1022 cm -3 down to below 0.06x 1022 cm-3, by a factor of seven as the GeH4 flow rate increased from 0 to 70 seem. A simultaneous decrease of O-H related bonds was also observed by a factor of 10 in the same germane flow range. The measured TE loss rates at λ=632.8 nm were found to increase from are 0.20 ± 0.02 to 6.46 ± 0.04 dB/cm as the germane flow rate increased from 5 to 50 seem, respectively. In contrast, the propagation loss values for TE polarization at λ-1550 nm were found to decrease from 0.32 ± 0.03 down to 0.14 ± 0.06 dB/cm for the same samples leading to the lowest values reported so far in the literature, eliminating the need for high temperature annealing as is usually done for these materials to be used in waveguide devices.Item Open Access Theoretical study of the insulating oxides and nitrides: SiO2, GeO2, Al2O3, Si3N4, and Ge3N4(Springer New York LLC, 2007) Sevik, C.; Bulutay, C.An extensive theoretical study is performed for wide bandgap crystalline oxides and nitrides, namely, SiO2, GeO2, Al 2O3, Si3N4, and Ge3N 4. Their important polymorphs are considered which are for SiO 2: α-quartz, α- and β-cristobalite and stishovite, for GeO2: α-quartz, and rutile, for Al2O 3: α-phase, for Si3N4 and Ge 3N4: α- and β-phases. This work constitutes a comprehensive account of both electronic structure and the elastic properties of these important insulating oxides and nitrides obtained with high accuracy based on density functional theory within the local density approximation. Two different norm-conserving ab initio pseudopotentials have been tested which agree in all respects with the only exception arising for the elastic properties of rutile GeO2. The agreement with experimental values, when available, are seen to be highly satisfactory. The uniformity and the well convergence of this approach enables an unbiased assessment of important physical parameters within each material and among different insulating oxide and nitrides. The computed static electric susceptibilities are observed to display a strong correlation with their mass densities. There is a marked discrepancy between the considered oxides and nitrides with the latter having sudden increase of density of states away from the respective band edges. This is expected to give rise to excessive carrier scattering which can practically preclude bulk impact ionization process in Si3N4 and Ge3N4.Item Open Access Thermally poled germanosilicate films with high second-order nonlinearity(IEEE, 2005) Özcan, A.; Digonnet, M. J. F.; Kino, G. S.; Ay, Feridun; Aydınlı, AtillaAccurate measurements of the second-order nonlinearity profile of thermally poled low-loss germanosilicate films grown on fused-silica substrates are reported, of interest as potential electro-optic devices. After optimization, we demonstrate a record high nonlinear coefficient d 33 ≈ 1.6 pm/V, a two-fold improvement over highest reported d 33 value in fused silica that we attribute to the presence of germanium.