Spectral properties of blue upconversion luminescences in Tm 3ϩ doped tellurite ͑PWT, PbF 2 -WO 3 -TeO 2 ͒ glasses and germanate ͑PWG, PbF 2 -WO 3 -GeO 2 ͒ glasses pumped by a tunable dye laser were studied at room temperature. Two emission bands centered at 453 and 477 nm, corresponding to the 1 D 2 → 3 H 4 and 1 G 4 → 3 H 6 transitions of Tm 3ϩ ions respectively, were observed. The two-photon absorption mechanism responsible for the 477 nm luminescence was confirmed by a quadratic dependence of luminescent intensities on the excitation power. Tellurite glasses showed a weaker upconversion luminescence than germanate glasses. This observation was inconsistent with the prediction from the phonon sideband measurement. In this article, Raman spectroscopy and transmittance measurement were employed to investigate the origin of the difference in upconversion luminescences in the two glasses. Compared with phonon sideband spectroscopy, Raman spectroscopy extracts more information, including both phonon energy and phonon density, and therefore, is a more effective analytical tool for understanding upconversion luminescence. Our results showed that the phonon energy as well as phonon density of the host glass is important in determining the upconversion efficiency.

Thin films of (1Ϫx)PbMg 1/3 Nb 2/3 O 3 -xPbTiO 3 ͑PMN-PT͒ with xϭ0, 0.1, 0.3, 0.35, and 0.4 have been fabricated on ͑001͒MgO single-crystal substrates by pulsed laser deposition ͑PLD͒. X-ray diffraction ͑XRD͒, scanning electron microscopy ͑SEM͒, and atomic force microscopy ͑AFM͒ were employed to characterize the structural properties of these PMN-PT films. Our results show that these films possess excellent structural properties and are cube-on-cube grown on ͑001͒MgO substrates. Spectroellipsometry ͑SE͒ was used to characterize the depth profiles, the microstructural inhomogeneities, including void and surface roughness, refractive indices and extinction coefficients of the films. In the analysis of the measured SE spectra, a double-layer Lorentz model with four oscillators was adopted to represent the optical properties of the PMN-PT films. In this model, the films were assumed to consist of two layers-a bottom bulk PMN-PT layer and a surface layer composed of bulk PMN-PT as well as void. Good agreement was obtained between the measured spectra and the model calculations. The film thickness measured by SEM is consistent with that obtained by SE while the root mean square ͑rms͒ surface roughness determined by AFM is also close to our fitted effective surface layer thickness obtained by SE. Our measurements show that the refractive indices of the PMN-PT films increase with PbTiO 3 contents. This dependence is consistent with our optical transmittance measurements which revealed that the energy band gaps of PMN-PT films decrease with increasing PbTiO 3 contents. The correlation between the energy band gap and the refractive index is discussed.

0.65 Pb(Mg 1/3 Nb 2/3 ) O 3 –0.35 PbTiO 3 (PMN–PT) thin films have been grown on MgO/TiN-buffered Si(001) substrates using pulsed laser deposition. Their structural properties and surface morphology were examined by x-ray diffraction and scanning electron microscopy, respectively. All PMN–PT films grown at 670 °C show a cube-on-cube epitaxial relationship of PMN–PT(100)∥MgO(100)∥TiN(100)∥Si(100). Discernable interfaces between layers in the heterostructures and crack-free surfaces are evident. A spectroscopic ellipsometer was used to study the optical characteristics of the films. It was revealed that the refractive index of the PMN–PT is ∼2.50 as measured at 635 nm. This value is only slightly less than that of the PMN–PT single crystal of 2.60. Our results suggest that the PMN–PT/MgO/TiN/Si heterostructure has an excellent potential for use in integrated optical waveguide devices.

High-quality ZnS:Mn thin films have been deposited on ͑001͒Si substrates at various temperatures using pulsed laser deposition. Their structural properties were characterized by x-ray diffraction. Optical studies by spectroscopic ellipsometry, optical transmittance, and photoluminescence measurements were systematically carried out on all film samples. In the analysis of the measured SE spectra, a modified double-layer Sellmeier model was adopted to represent the optical properties of the ZnS:Mn films. In this model, the films were assumed to consist of two layers-a bottom bulk ZnS:Mn layer and a surface layer composed of bulk ZnS:Mn as well as void. Good agreement was obtained between the measured spectra and the model calculations. Changes in the refractive indices of the ZnS:Mn films as a function of growth temperature were investigated. The PL and absorption measurements revealed that the orange-yellow emission band at ϳ590 nm and the absorption edge at ϳ370 nm upshifted to shorter wavelengths for films deposited at higher substrate temperatures. These results imply that the energy gap of the ZnS:Mn films increases with growth temperature. The observed changes of optical properties in these films are correlated to their structural qualities.

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