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Spectral Dependence (spectral + dependence)

Distribution by Scientific Domains
Physics and Astronomy75%

Selected Abstracts

Growth and optical characterization of Cd1- xBexSe and Cd1- xMgxSe crystals

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 4-5 2005
F. Firszt
Abstract Cd1- xBexSe and Cd1- xMgxSe solid solutions were grown from the melt by the high pressure Bridgman method. Optical, luminescence and photothermal properties of these materials were investigated. Spectroscopic ellipsometry was applied for determination of the spectral dependence of the complex dielectric function (E) and refractive index n(E) at room temperature in the photon energy range 0.75-6.5 eV for samples with optic axis (c-axis) perpendicular to the air-sample interface. The critical point (CP) parameters for E0 and E1 transitions were determined using a standard excitonic CP function to fit the numerically calculated differential spectra ,2,2/,E2. The dispersion of the refractive index of the alloys was modelled using a Sellmeier-type relation. The values of fundamental and exciton band-gap energies were estimated from the ellipsometric and photoluminescence measurements. The origin of luminescence in Cd1- xBexSe and Cd1- xMgxSe was discussed. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Disorder-induced modification of the attenuation of light in a two-dimensional photonic crystal with complete band gap

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2003
M. A. Kaliteevski
Abstract We report on the modeling of light transmission in disordered two-dimensional photonic crystals (formed by air cylinders etched in a dielectric slab) with a complete photonic band gap. The disorder leads to a decrease in the light attenuation in the transmission dip corresponding to the photonic band gap, both for straight and scattered transmission, but the dependence of the attenuation length on the disorder is quite different for straight and scattered transmission. In the case of the straight transmission, there is a threshold degree of disorder required for the increase of the attenuation length. Disorder leads to a substantial modification of the spectral shape in the frequency region, corresponding to the photonic band gap, in particular, to the decrease of the width of the spectral dependence of the inverse attenuation length. We also demonstrate the appearance of photonic mini-bands in the photonic band gaps in the case of disorder represented by randomly distributed ,vacancies' of the air-cylinders. [source]

Characterisation of Cd1,x,yZnxBeySe crystals by spectroscopic ellipsometry and luminescence

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2006
A. A. Wronkowska
Abstract Optical and luminescence properties of Cd1,x,yZnxBeySe solid solutions grown in the composition range 0 < x < 0.15 and 0 < y < 0.30 by the high pressure Bridgman method are reported. Spectroscopic ellipsometry was employed for determination of spectral dependence of the complex dielectric function ,(E), refractive index n(E) and absorption coefficient ,(E) in the photon energy range 0.75,6.0 eV. The dispersion of the refractive index of the alloys was modelled using a Sellmeier-type relation. The excitonic band-gap energies were estimated from the ellipsometric and photoluminescence measurements. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

UVA1 and UVB irradiated skin investigated by optical coherence tomography in vivo: a preliminary study

CLINICAL & EXPERIMENTAL DERMATOLOGY, Issue 1 2005
T. Gambichler
Summary In histological studies, it has frequently been demonstrated that ultraviolet (UV) exposure, in particular UVB, can induce significant thickening of the viable epidermis and/or stratum corneum. Since skin biopsy alters the original skin morphology and always requires an iatrogenic trauma, we aimed to introduce optical coherence tomography (OCT) in vivo for the investigation of changes of epidermal thickness (ET) following UVA1 and UVB irradiation. Twelve healthy subjects received daily 60 J/cm2 of UVA1 and 1.5 minimal erythema doses UVB on their upper back over 3 consecutive days. Twenty-four hours after the last irradiation, OCT assessments were performed on UV exposed and adjacent nonirradiated control sites. Data of ET as expressed by comparison of the averaged A-scans differed significantly between nonirradiated (94.2 ± 15.7 µm), UVA1 (105.4 ± 12.8 µm) and UVB (125.7 ± 22.1 µm) exposed sites. In comparison to the nonirradiated sites, UVA1 exposed skin showed significant (P = 0.022) increase of ET of 11% and UVB exposed sites a significant (P < 0.001) increase of 25%. ET of UVA1 and UVB exposed skin sites differed significantly (P =0.005). Our results obtained from OCT in vivo measurements confirm data of previous histological studies indicating that not only erythemogenic doses of UVB, but also suberythemogenic doses of UVA1 may have a significant impact on ET. OCT appears to be a promising bioengineering technique for photobiological studies. However, further studies are needed to establish its measurement precision and validity, and to investigate in vivo spectral dependence on UV induced skin changes such as skin thickening. [source]