B. Sudhakar Reddy

Spectroscopic Investigations of Sm3+ Ions Doped B2O3-Bi2O3-ZnO-Li2O Glasses

This article reports on the preparation and optical properties of Sm3+ ions doped B2O3-Bi2O3-ZnO-Li2O (ZLiBiB) glasses. The optical absorption spectra, luminescence spectra and decay curves were measured. On the basis of Judd-Ofelt theory, the intensity parameters Ωλ (λ = 2, 4, 6) and also oscillatory strengths are obtained from the absorption spectra and these results were used to compute the radiative properties of Sm3+: ZLiBiB glasses. Especially the luminescence concentration quenching and the related mechanism were analysed systematically.

Spectroscopic investigations of Er3+:CdO–Bi2O3–B2O3 glasses

This article reports on the optical properties of Er3+ ions doped CdO-Bi2O3-B2O3 (CdBiB) glasses. The materials were characterized by optical absorption and emission spectra. By using Judd-Ofelt theory, the intensity parameters Ω(λ) (λ = 2, 4, 6) and also oscillatory strengths were calculated from the absorption spectra. The results were used to compute the radiative properties of Er3+ :CdBiB glasses. The concentration quenching and energy transfer from Yb3+ -Er3+ were explained. The stimulated emission cross-section, full width at half maximum (FWHM) and FWHM × σpE values are also calculated for all the Er3+ CdBiB glasses.

Emission Properties of RE3+ (RE = Eu, Tb): CdO-Li2O-B2O3-TeO2 Glasses

Eu3+ or Tb3+ ions doped Cadmium lithium boro tellurite (CLiBT) glasses with different compositions were prepared by melt quenching method. The non-crystalline nature of the glasses has been verified by the XRD measurements. The photoluminescent properties were characterized with excitation and emission spectra. The emission spectra of Eu3+: CLiBT glasses measured with λexci = 392 nm (7F0→5L6) have shown five emission transitions at 578 nm, 592 nm, 612 nm, 652 nm, 701 nm and are assigned to the transitions 5D0→7F0,7F1,7F2,7F3 &7F4 respectively. Among these, the transition at 612 nm (5D0→7F2) has shown a bright red emission. In the case of Tb3+:CLiBT glasses upon excitation with 376 nm (7F6 → 5G6), the emission transitions have been observed at 436 nm, 456 nm, 450 nm, 467 nm, 488 nm, 508 nm, 542 nm, 583 nm, 612 nm, 653 nm and are assigned to the transitions 5D3→7F4,7F3,7F3 & 5D4→7F6,7F6, 7F5,7F4,7F3 &7F2 respectively. Among these, the transition at 542 nm (5D4→7F5) has shown a bright green emission. In this work, we have reported the emission properties of Eu3+ and Tb3+: CLiBT glasses to explore them as novel display materials.

Optical absorption and photoluminescence studies of Dy3+: LCZSFB glasses

The paper presents the way that colour can serve solving the problem of calibration points indexing in a camera geometrical calibration process. We propose a technique in which indexes of calibration points in a black-and-white chessboard are represented as sets of colour regions in the neighbourhood of calibration points. We provide some general rules for designing a colour calibration chessboard and provide a method of calibration image analysis. We show that this approach leads to obtaining better results than in the case of widely used methods employing information about already indexed points to compute indexes. We also report constraints concerning the technique. Nowadays we are witnessing an increasing need for camera geometrical calibration systems. They are vital for such applications as 3D modelling, 3D reconstruction, assembly control systems, etc. Wherever possible, calibration objects placed in the scene are used in a camera geometrical calibration process. This approach significantly increases accuracy of calibration results and makes the calibration data extraction process easier and universal. There are many geometrical camera calibration techniques for a known calibration scene [1]. A great number of them use as an input calibration points which are localised and indexed in the scene. In this paper we propose the technique of calibration points indexing which uses a colour chessboard. The presented technique was developed by solving problems we encountered during experiments with our earlier methods of camera calibration scene analysis [2]-[3]. In particular, the proposed technique increases the number of indexed points points in case of local lack of calibration points detection. At the beginning of the paper we present a way of designing a chessboard pattern. Then we describe a calibration point indexing method, and finally we show experimental results. A black-and-white chessboard is widely used in order to obtain sub-pixel accuracy of calibration points localisation [1]. Calibration points are defined as corners of chessboard squares. Assuming the availability of rough localisation of these points, the points can be indexed. Noting that differences in distances between neighbouring points in calibration scene images differ slightly, one of the local searching methods can be employed (e.g. [2]). Methods of this type search for a calibration point to be indexed, using a window of a certain size. The position of the window is determined by a vector representing the distance between two previously indexed points in the same row or column. However, experiments show that this approach has its disadvantages, as described below. * E-mail: A.Nowakowski@ire.pw.edu.pl Firstly, there is a danger of omitting some points during indexing in case of local lack of calibration points detection in a neighbourhood (e.g. caused by the presence of non-homogeneous light in the calibration scene). A particularly unfavourable situation is when the local lack of detection effects in the appearance of separated regions of detected calibration points. It is worth saying that such situations are likely to happen for calibration points situated near image borders. Such points are very important for the analysis of optical nonlinearities, and a lack of them can significantly influence the accuracy of distortion modelling. Secondly, such methods may give wrong results in the case of optical distortion with strong nonlinearities when getting information about the neighbouring index is not an easy task. Beside this, the methods are very sensitive to a single false localisation of a calibration point. Such a single false localisation can even result in false indexing of a big set of calibration points. To avoid the above-mentioned problems, we propose using a black-and-white chessboard which contains the coded index of a calibration point in the form of colour squares situated in the nearest neighbourhood of each point. The index of a certain calibration point is determined by colours of four nearest neighbouring squares (Fig.1). An order of squares in such foursome is important. Because the size of a colour square is determined only by the possibility of correct colour detection, the size of a colour square can be smaller than the size of a black or white square. The larger size of a black or white square is determined by the requirements of the exact localisation step which follows the indexing of calibration points [3]. In this step, edge information is extracted from a blackand-white chessboard. This edge information needs larger Artur Nowakowski, Wladyslaw Skarbek Institute of Radioelectronics, Warsaw University of Technology, Nowowiejska 15/19, 00-665 Warszawa, A.Nowakowski@ire.pw.edu.pl Received February 10, 2009; accepted March 27, 2009; published March 31, 2009 http://www.photonics.pl/PLP

Synthesis and luminescence properties of Ca3Ga2Si3O12:RE3+ (RE = Eu/Tb) powder phosphors

Rare earth ions (Eu(3+) or Tb(3+) )-activated Ca(3) Ga(2) Si(3) O(12) (CaGaSi) phosphors were synthesized by using a sol-gel method. Photoluminescence spectra of Eu(3+):CaGaSi phosphors exhibited five emission bands at 578, 592, 612, 652 and 701 nm, which were assigned to the transitions ((5)D(0) → (7)F(0), (7)F(1,)(7)F(2), (7)F(3) and (7)F(4)), respectively, with an excitation wavelength of λ(exci) = 392 nm. Among these, the transition (5) D(0) → (7) F(2) (612 nm) displayed bright red emission. In the case of Tb(3+):CaGaSi phosphors, four emission bands were observed at 488 ((5)D(4) → (7)F(6)), 543 ((5)D(4) → (7)F(5)), 584 ((5)D(4) → (7)F(4)) and 614 nm ((5)D(4) → (7) F(3) ) from the measurement of PL spectra with λ(exci) = 376 nm. Among these, the transition (5)D(4) → (7) F(5) at 543 nm displayed bright green emission. The structure and morphology of the phosphors were studied from the measurements of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDAX) results.

Synthesis, Structural and Photoluminescence Properties of RE3+ (RE = Pr, Tm): (Mg Ca)2Bi4Ti5O20 Ceramics

Pr3+ and Tm3+ (0.2 mol %) ions doped magnesium calcium bismuth titanate [(MgCa)2 Bi4Ti5O20] ceramics were synthesized by conventional solid state reaction method. The structural and morphological properties of prepared ceramic powders were studied by using XRD and SEM profiles. The elemental analysis and FTIR spectra of the prepared ceramics have been analyzed. Emission spectrum of Pr3+: (MgCa)2Bi4Ti5O20 ceramic powder has shown strong red emission at 614 nm (3P0 → 3H6) with an excitation wavelength λexci = 452 nm (3H4 → 3P2) and Tm3+: (MgCa)2Bi4Ti5O20 ceramic powder has shown blue emission at 477 nm (1G4 → 3H6) with an excitation wavelength λexci = 367 nm (3H6 → 1D2).

Spectroscopic Studies of RE3+(RE = Eu, Tb, Sm & Dy): Lithium Lead Boro Tellurite Glasses

0.25, 0.5, 1.0 and 2.0 mol% of rare earth ions (Eu3+, Tb3+, Sm3+and Dy3+) doped lithium lead boro tellurite glasses have been prepared. From the measured absorption and emission spectra, optical properties have been studied. The absorption spectrum of Eu3+: glass has shown three absorption bands at 394 nm, 465 nm and 533 nm, Tb3+: glass has shown a weak absorption band at 484 nm, Sm3+: glass has shown nine absorption bands at 477 nm, 563 nm, 946 nm, 1081 nm, 1231 nm, 1378 nm, 1482 nm,1525 nm and 1589 nm, Dy3+: glass has shown six absorption bands at 751 nm, 797 nm,900 nm, 1091 nm, 1274 nm and 1680 nm. From Eu3+: glasses, a red emission at 612 nm (5D0 → 7F2) with λexci = 392 nm, Tb3+: glasses, a green emission at 543 nm (5D4 → 7F5) with λexci = 376 nm, Sm3+: glasses, an orange-red emission at 598 nm (4G5/2 → 6H7/2) with λexci = 401 nm and also from Dy3+: glasses, a yellow emission at 574 nm (4F9/2 → 6H13/2) with λexci = 451 nm have been observed. For all these emission bands decay curves have been plotted to evaluate their life times and the emission mechanism that arised in the glasses have been explained in terms of energy level diagrams.

Emission analysis of RE3+ (RE = Sm, Dy):B2O3-TeO2-Li2O-AlF3 glasses

This article reports on the optical properties of 0.5% mol of Sm(3+), Dy(3+) ion-doped B2O3-TeO2-Li2O-AlF3 (LiAlFBT) glasses. The glass samples were characterized by optical absorption and emission spectra. Judd-Ofelt theory was applied to analyze the optical absorption spectra and calculate the intensity parameters and radiative properties of the emission transitions. The emission spectra of Sm(3+) and Dy(3+):LiAlFBT glasses showed a bright reddish-orange emission at 598 nm ((4)G5/2 → (6)H7/2) and an intense yellow emission at 574 nm ((4)F9/2 → (6)H13/2), respectively. Full width at half maximum (FWHM), stimulated emission cross section, gain bandwidth and optical gain values were also calculated to extend the applications of the Sm(3+) and Dy(3+):LiAlFBT glasses.

Spectroscopic investigations of Eu3+ and Tb3+: Cadmium lead boro tellurite glasses

This paper reports on the preparation and spectral properties of europium (Eu3+) and terbium (Tb3+) ions doped cadmium lead boro tellurite (CLBT) glasses. For reference glasses, physical properties have been evaluated. From the [measurements of X-ray diffraction (XRD), glass amorphous nature of these [glasses has been studied. From the emission spectra of Eu3+: CLBT glasses, five [transitions (5D0 → 7F0, 7F1, 7F2, 7F3 and 7F4) at 579, 591, 613, 652 and 701 nm are observed with λexci = 392 nm (7F0 → 5L6) and in the case of Tb3+: CLBT glasses, four emission transitions 5D4 → (7F6, 7F5, 7F4 and 7F3) are observed at 489, 543, 584 and 621nm respectively monitered with λexci = 376 nm (7F6 → 5G6).

Optical analysis of Sm3+ and Dy3+ ion-doped cadmium lead boro tellurite glasses

This paper reports on the spectral results of Sm3+ or Dy3+ ion-doped optical glasses in the following composition: Their X-ray diffraction profiles confirm the amorphous nature of these rare-earth ion-doped glasses. These glasses have shown strong absorption bands in the near-infrared region. The emission spectrum of Sm3+-doped glasses exhibit four emission transitions at 562 nm (4G 5/2→6H 5/2), 598 nm (4G 5/2→6H 7/2), 645 nm (4G 5/2→6H 9/2) and 705 nm (4G 5/2→6H 11/2) with 471 nm (4G 5/2→6I 11/2) as the excitation. Among these, the transition (4G 5/2→6H 7/2) at 598 nm has shown a strong emission. The emission spectrum of Dy3+-doped glass has shown three emission transitions at 482 nm (4F 5/2→6H 15/2), 574 nm (4F 9/2→6H 13/2) and 664 nm (4F 9/2→6H 13/2) with an excitation at 451 nm (6H 15/2→6I 15/2). Upon exposure to UV radiation, Sm3+ and Dy3+ glasses have shown bright reddish-orange and bright yellow colors, respectively, from their surfaces. The emission mechanisms that arise in these glasses have been explained in terms of energy level schemes.