Papers by Keyword: Optical Absorption

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Authors: Ahmad Marzuki, Mohtar Yunianto, Riyatun, Hery Purwanto
Abstract: Absorption spectra of different composition of tellurite glasses were analyzed in order to estimate their lasing properties. Composition of the investigated tellurite glasses are: 55TeO2-(43-x)ZnO-2Bi2O3-xEr2O3 (x = 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 mol%). Glasses absorption spectra and density were measured at room temperature using UV-VIS-NIR Spectrophotometer and pycnometer, respectively; while their refractive index were measured by implying Brewster’s angle method. Lasing performance of glasses were then analyzed using Judd-Ofelt theory in order to obtain line strength (S), Judd-Ofelt parameters (Ωt, t = 1, 2, 3), and radiative life-times (τ). It is seen that incorporating Er3+ ions of up to 2.5 mol% resulted in decreasing the radiative lifetime of electrons sitting at 4I11/2. From Judd-Ofelt parameters analysis it can be concluded that these tellurite glasses tend to have the covalence nature of Er-O bond and thus represents the asymmetry around the Er3+ ions site.
Authors: Walter R.L. Lambrecht, Sukit Limpijumnong, Sergey N. Rashkeev, Benjamin Segall
Authors: Pavol Fedorko, V. Skákalová, O. Foltin, F. Kolenic, V. Šmatko
Authors: G. Farhi, R. Cherfi, M. Aoucher, K. Zellama
Authors: A.A.I. Al-Bassam, U.A. Elani
Abstract: Thin films CuInSe2 (CIS) cells have been fabricated by the electro chemical method. Some of the physical properties such as lattice parameter, crystal structure and grain size of CuInSe2 (CIS) films with different Cu/In ratios ( 0.50-1.1) were determined using X-ray diffractornetry. The surface morphology with different Cu/In ratios was studied using a scanning electron microscope. The SEM studies on these films showed that the grain size increases the Cu/In ratios increases from 0.49 to 1.1. The variation of the band gap with different Cu/In ratio was determined from optical absorption measurements. The results showed that the band gap decreases as the Cu/In ratio increases over the considered range of composition. Key words: Thin films, Lattice Parameter , Optical Absorption, grain size
Authors: Hui Chiang Teoh, Sabar Derita Hutagalung
Abstract: Silicon nanowires (SiNWs) are important candidate for high performance electronic and optoelectronic devices due to their unique structures, electrical and optical properties. SiNWs were fabricated by silver-assisted electroless etching of Si wafer. Vertically aligned SiNW arrays with length about 8.75 μm and diameter of less than 90 nm have been fabricated. The reflectance of SiNWs without dye (12%) is greatly lower compared to bare Si wafer (25%). Therefore, SiNWs on Si substrate can be used as a good anti-reflection layer for a wide range of incident light. The reflectance of dye-sensitized SiNWs with red, green and blue dyes is 7%, 5.5%, and 5% respectively. The results confirmed that the reflectance of SiNWs with dye is much lower compared to SiNWs without dye and bare Si wafer. It was proven that dye on SiNWs can be used to reduce the reflectance (improved absorption) about 40% compared to SiNWs without dye.
Authors: Tamihiro Gotoh, Kenta Kawarai, Hiroki Wakabayashi, Kenji Kaneda
Abstract: Optical absorption in amorphous InGaZnO4 films was examined by optical transmittance and photothermal spectroscopy using individual cantilever. The amorphous InGaZnO4 films have optical bandgap of ~3.5 eV, and Urbach tail absorption and mid-gap absorption at 2.0-3.0 eV. Mid-gap absorption was reduced by thermal annealing at 300 °C in an atmosphere. This observation indicates that heat-induced structural change causes reduction of gap states in amorphous InGaZnO4 films.
Authors: Iman Santoso, Ram Sevak Singh, Pranjal Kumar Gogoi, Teguh Citra Asmara, Da Cheng Wei, Wei Chen, Andrew T.S. Wee, Vitor M. Pereira, Andrivo Rusydi
Abstract: The significant alteration of absorption (A) of monolayer graphene under mild oxygen plasma exposure has been observed. The first important effect is the reduction of the excitonic resonance peak at 4.64 eV. Secondly, in the near infrared range, A is gradually suppressed below an exposure-dependent threshold in sense that A << A0. Quantity A0 (given by πα and α is the fine structure constant) denotes constant absorption and relates to universal optical conductivity σ0. The suppression of A0 can be thought as the weakening of electron-hole interaction as displayed by the reduction of the excitonic resonance peak at 4.64 eV. The weakening of this interaction is due to the disorder introduced by the oxygen plasma exposure.
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