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Kazuyuki Hirao - One of the best experts on this subject based on the ideXlab platform.
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Photochemical reactions of samarium ions in Sodium Borate glasses irradiated with near-infrared femtosecond laser pulses
Journal of Luminescence, 2002Co-Authors: Koji Fujita, Chikafumi Yasumoto, Kazuyuki HiraoAbstract:Abstract Photoinduced processes of Sm3+-doped Sodium Borate glasses under high-power, 800 nm femtosecond laser irradiation have been studied. Both the photoreduction of Sm3+ to Sm2+ and the formation of intrinsic defects are observed at an irradiance well below the threshold for laser-induced damage. We propose that these photoinduced processes arise from the linear and two-photon absorption of the short-wavelength component of the supercontinuum and the subsequent ionization of the glass matrix. Photochemical hole burning (PHB) has been observed for 5 D 0 – 7 F 0 transition of Sm2+ in the Sodium Borate glasses irradiated with near-infrared femtosecond laser pulses. The efficiency of hole burning at 77 K was about 5 times higher in the irradiated glasses than in thermally reduced glasses. We consider that both the metastable Sm2+ and the intrinsic defects were responsible for the highly efficient PHB phenomenon.
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Ultrashort-laser-pulse-induced persistent spectral hole burning of Eu(3+) in Sodium Borate glasses.
Optics letters, 2001Co-Authors: Koji Fujita, Masayuki Nishi, Kazuyuki HiraoAbstract:We have observed persistent spectral hole burning (PSHB) in Eu3+-doped Sodium Borate glasses irradiated with near-IR femtosecond laser pulses. As-prepared glasses, i.e., glasses melted in air, do not show PSHB even at low temperatures ∼77 K, but room-temperature PSHB occurs in the irradiated glasses. The exposure to IR radiation causes both the reduction of Eu3+ to Eu2+ and the formation of intrinsic defects. We propose that the photoinduced redistribution of electric charges between Eu3+ to Eu2+ is responsible for the occurrence of PSHB.
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room temperature photochemical hole burning of eu3 in Sodium Borate glasses
Journal of Physics: Condensed Matter, 2001Co-Authors: Koji Fujita, Masayuki Nishi, Katsuhisa Tanaka, Kazuyuki HiraoAbstract:Persistent spectral hole burning (PSHB) has been observed at 77 K to room temperature for Eu3+ in Sodium Borate glasses with compositions of xNa2O(100-x)B2O3 (x = 10,25,35). Glasses melted in air do not show the phenomenon of PSHB, while room-temperature PSHB occurs in the glasses prepared by melting in reducing conditions. 151Eu Mossbauer spectra reveal that europium ions are present as both Eu3+ and Eu2+ in glasses melted in reducing conditions. The relative hole area increases with an increase in the molar ratio of Eu2+ to Eu3+ when the content of Eu2+ is low, whereas the relative hole is almost independent of the molar fraction of Eu2+ when the content of Eu2+ is high. Furthermore, a comparison of hole burning among Sodium Borate glasses with the molar fraction of Eu2+ being almost the same as one another shows that the hole area grows larger as the content of Na2O becomes higher. These observations are interpreted in terms of the photoinduced redistribution of electric charges between Eu3+ and Eu2+. The effect of the glass composition on hole widths is also discussed based on the structural change in Sodium Borate glasses.
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Room-temperature persistent spectral hole burning of Eu3+-doped Sodium Borate glasses
Journal of Luminescence, 2000Co-Authors: Koji Fujita, Katsuhisa Tanaka, Kazumi Yamashita, Kazuyuki HiraoAbstract:Abstract Persistent spectral hole burning has been observed at room temperature for Eu3+ incorporated in Sodium Borate glasses prepared under reducing conditions. The measurements at 77 K indicate that the relative hole area increases with increasing the molar ratio of Eu2+ to Eu3+ when the content of Eu2+ is low, whereas the relative hole is almost independent of the molar fraction of Eu2+ when the content of Eu2+ is high. We suggest that photoinduced reduction of Eu3+ is responsible for the room-temperature hole burning of Eu3+ in the present Sodium Borate glasses and that the predominant center which captures a positive hole formed by the reduction of Eu3+ is the coexisting Eu2+.
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infrared femtosecond laser induced visible long lasting phosphorescence in mn2 doped Sodium Borate glasses
Japanese Journal of Applied Physics, 1999Co-Authors: Jianrong Qiu, Yuki Kondo, Kiyotaka Miura, Tsuneo Mitsuyu, Kazuyuki HiraoAbstract:We report on the long-lasting phosphorescence phenomenon in Mn2+-doped Sodium Borate glass. After scanning by a focused 800 nm femtosecond laser for 10 s, the path traversed by the focal point of the laser in the glass emits reddish long-lasting phosphorescence visible to the naked eye in the dark five minutes after the removal of the activating laser. Absorption spectra of the glass showed that defect centers were induced after laser irradiation, and the absorption due to the laser-induced defect centers decayed with time. The long-lasting phosphorescence is considered to be due to the thermostimulated recombination of holes and electrons at traps induced by the laser irradiation, and energy transfer from the composite defect centers to Mn2+ ions.
Koji Fujita - One of the best experts on this subject based on the ideXlab platform.
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Photochemical reactions of samarium ions in Sodium Borate glasses irradiated with near-infrared femtosecond laser pulses
Journal of Luminescence, 2002Co-Authors: Koji Fujita, Chikafumi Yasumoto, Kazuyuki HiraoAbstract:Abstract Photoinduced processes of Sm3+-doped Sodium Borate glasses under high-power, 800 nm femtosecond laser irradiation have been studied. Both the photoreduction of Sm3+ to Sm2+ and the formation of intrinsic defects are observed at an irradiance well below the threshold for laser-induced damage. We propose that these photoinduced processes arise from the linear and two-photon absorption of the short-wavelength component of the supercontinuum and the subsequent ionization of the glass matrix. Photochemical hole burning (PHB) has been observed for 5 D 0 – 7 F 0 transition of Sm2+ in the Sodium Borate glasses irradiated with near-infrared femtosecond laser pulses. The efficiency of hole burning at 77 K was about 5 times higher in the irradiated glasses than in thermally reduced glasses. We consider that both the metastable Sm2+ and the intrinsic defects were responsible for the highly efficient PHB phenomenon.
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Ultrashort-laser-pulse-induced persistent spectral hole burning of Eu(3+) in Sodium Borate glasses.
Optics letters, 2001Co-Authors: Koji Fujita, Masayuki Nishi, Kazuyuki HiraoAbstract:We have observed persistent spectral hole burning (PSHB) in Eu3+-doped Sodium Borate glasses irradiated with near-IR femtosecond laser pulses. As-prepared glasses, i.e., glasses melted in air, do not show PSHB even at low temperatures ∼77 K, but room-temperature PSHB occurs in the irradiated glasses. The exposure to IR radiation causes both the reduction of Eu3+ to Eu2+ and the formation of intrinsic defects. We propose that the photoinduced redistribution of electric charges between Eu3+ to Eu2+ is responsible for the occurrence of PSHB.
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room temperature photochemical hole burning of eu3 in Sodium Borate glasses
Journal of Physics: Condensed Matter, 2001Co-Authors: Koji Fujita, Masayuki Nishi, Katsuhisa Tanaka, Kazuyuki HiraoAbstract:Persistent spectral hole burning (PSHB) has been observed at 77 K to room temperature for Eu3+ in Sodium Borate glasses with compositions of xNa2O(100-x)B2O3 (x = 10,25,35). Glasses melted in air do not show the phenomenon of PSHB, while room-temperature PSHB occurs in the glasses prepared by melting in reducing conditions. 151Eu Mossbauer spectra reveal that europium ions are present as both Eu3+ and Eu2+ in glasses melted in reducing conditions. The relative hole area increases with an increase in the molar ratio of Eu2+ to Eu3+ when the content of Eu2+ is low, whereas the relative hole is almost independent of the molar fraction of Eu2+ when the content of Eu2+ is high. Furthermore, a comparison of hole burning among Sodium Borate glasses with the molar fraction of Eu2+ being almost the same as one another shows that the hole area grows larger as the content of Na2O becomes higher. These observations are interpreted in terms of the photoinduced redistribution of electric charges between Eu3+ and Eu2+. The effect of the glass composition on hole widths is also discussed based on the structural change in Sodium Borate glasses.
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Room-temperature persistent spectral hole burning of Eu3+-doped Sodium Borate glasses
Journal of Luminescence, 2000Co-Authors: Koji Fujita, Katsuhisa Tanaka, Kazumi Yamashita, Kazuyuki HiraoAbstract:Abstract Persistent spectral hole burning has been observed at room temperature for Eu3+ incorporated in Sodium Borate glasses prepared under reducing conditions. The measurements at 77 K indicate that the relative hole area increases with increasing the molar ratio of Eu2+ to Eu3+ when the content of Eu2+ is low, whereas the relative hole is almost independent of the molar fraction of Eu2+ when the content of Eu2+ is high. We suggest that photoinduced reduction of Eu3+ is responsible for the room-temperature hole burning of Eu3+ in the present Sodium Borate glasses and that the predominant center which captures a positive hole formed by the reduction of Eu3+ is the coexisting Eu2+.
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Faraday effect of Sodium Borate glasses containing divalent europium ions
Journal of Applied Physics, 1997Co-Authors: Katsuhisa Tanaka, Koji Fujita, Naohiro Soga, Jianrong Qiu, Kazuyuki HiraoAbstract:Faraday effect measurements have been carried out at room temperature for some Sodium Borate glasses containing Eu2+ ions prepared under a reducing atmosphere. The wavelength dependence of the Verdet constant is analyzed in terms of a theory derived by Van Vleck and Hebb to obtain effective transition wavelength of the 4f7→4f65d transition which causes the Faraday effect of Eu2+ in the visible range. The effective transition wavelength increases with an increase in the optical basicity of glass. This phenomenon is explained in terms of the crystal field theory; because the splitting of 5d levels is larger in the glass with larger optical basicity, the energy required for the 4f7→4f65d transition decreases as the optical basicity of glass increases. The magnitude of Verdet constant increases with an increase in the effective transition wavelength when the concentration of EuO remains constant.
Myeongkyu Lee - One of the best experts on this subject based on the ideXlab platform.
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Crystalline patterning in Sm-doped Sodium Borate glass by CW Nd:YAG laser irradiation
Applied Surface Science, 2007Co-Authors: Yusok Lim, Myeongkyu LeeAbstract:Abstract Laser irradiation of glass materials has drawn much attention because this technique can offer a new processing method for spatially selected structural modification and/or crystallization in glass. Crystallized line and dot patterns at the micrometer scale were fabricated on the surface of Sm-doped Sodium Borate (Na2O–B2O3) glass by irradiation of a continuous-wave Nd:YAG laser at λ = 1064 nm. The pattern sizes could be controlled by adjusting such parameters as scan rate, exposure time, and laser power. Analyses by Raman spectroscopy and X-ray diffraction revealed that the crystalline phase is Na3Sm2(BO3)3.
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Femtosecond laser induced PL change in Sm-doped Sodium Borate glass and 3D optical memory
Journal of Luminescence, 2006Co-Authors: Seungphil Lee, Myeongkyu Lee, Ki-soo LimAbstract:Abstract We report on a femtosecond laser-induced photoluminescence (PL) change in Sm-doped Sodium-Borate glass and its potential application to three-dimensional optical memory. Irradiation with a femtosecond pulsed laser (800 nm, 1 kHz, 100 fs) induced a new PL peak near 682 nm, resulting from the photoreduction of Sm ions from Sm3+ to Sm2+. This makes it possible to readout the stored data by detecting the new PL peak as a signal. Multilayer patterns of various dot sizes and interlayer spacings were fabricated by femtosecond pulsed laser. These patterns were read out by a fluorescent confocal microscope which detected the emission at 682 nm as a signal. Here we discuss the feasibility of 3D optical memory by use of PL change in Sm-doped Sodium Borate glass.
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Laser-induced defect centers and valence state change of Mn ions in Sodium Borate glasses
Journal of Luminescence, 2006Co-Authors: Sunkyun Lee, Ki-soo Lim, Minh-tuan Trinh, Myeongkyu Lee, Jung-rim Nam, Eunkyoung KimAbstract:Abstract In this report, an ultrafast laser was used to produce persistent change of valence states of Mn ions in Sodium Borate glasses. Glass composition of Sodium Borate in this study was 85B 2 O 3 –15Na 2 O. We observed a broad emission at 600 nm of the transition 4 T 1 – 6 A 1 of doped Mn 2+ ions with excitation at 325 nm in an unirradiated area. Femtosecond laser irradiation produced additional strong blue emission at 440 nm and reduced the emission intensity from Mn 2+ ions. The irradiation produced the absorption band of Mn 3+ at 550 nm, resulting in color change of the glass. The blue band was measured as a function of irradiation exposure for samples with various concentrations of Mn ions. The valence state change of Mn 2+ to Mn 3+ was suppressed in Mn and Cr codoped glasses.
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Femtosecond laser-induced reduction in Eu-doped Sodium Borate glasses
Journal of Luminescence, 2006Co-Authors: Ki-soo Lim, Sunkyun Lee, Minh-tuan Trinh, Suk-ho Kim, Myeongkyu Lee, D.s. Hamilton, George N. GibsonAbstract:Abstract In this work, we report permanent reduction of Eu 3+ to Eu 2+ in Sodium Borate glasses by irradiation of near-infrared femtosecond laser. Glass composition of Sodium Borate was 85B 2 O 3 –15Na 2 O. The glasses were doped with 0.05, 0.1, and 0.5 mol% Eu 2 O 3 . Absorption and fluorescence dynamics were studied to investigate valence state change of europium ions and the energy transfer between Eu 2+ and Eu 3+ ions. As the femtosecond laser intensity or exposure time increases, the emission band at 400 nm becomes stronger. However, the photoreduction efficiency decreases as the dopant concentration increases. We discuss the photoreduction mechanism under multiphoton absorption.
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3D Optical Memory by Photoluminescence Change in Sm-doped Sodium Borate Glass
Integrated Photonics Research and Applications Nanophotonics for Information Systems, 2005Co-Authors: Myeongkyu Lee, Sunkyun Lee, Jinhyong Lim, Eunkyoung Kim, Ki-soo LimAbstract:We observed femtosecond laser-induced photoluminescence (PL) change in Sm-doped Sodium-Borate glass. Recording and readout of the multi-layer dot patterns by use of this spectral change are here discussed
C.s. Menon - One of the best experts on this subject based on the ideXlab platform.
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Preparation and physical properties of CuPc substituted Sodium Borate glass matrix
Materials Letters, 2002Co-Authors: Cyriac Joseph, P.r Binu, K Shreekrishnakumar, C.s. MenonAbstract:Electrical conductivity and optical absorption of copper phthalocyanine (CuPc) substituted Sodium Borate glass is reported here for the first time. We have successfully prepared CuPc substituted Sodium Borate glass at 830 °C and some preliminary studies on this glass are reported. Activation energy and optical band gap were determined for the glass from the Arrhenius plot of conductivity and optical absorption spectra, respectively.
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Preparation and physical properties of nickel phthalocyanine-substituted Sodium Borate glass
Materials Letters, 2002Co-Authors: P.r Binu, Cyriac Joseph, K Shreekrishnakumar, C.s. MenonAbstract:Electrical conductivity and optical absorption of nickel phthalocyanine (NiPc)-substituted Sodium Borate glass is reported here. We have successfully prepared NiPc-substituted Sodium Borate glass at 830 °C, and some preliminary studies on this glass are reported. Activation energy and optical band gap were determined for the glass from the Arrhenius plot of conductivity and optical absorption spectra, respectively.
Ki-soo Lim - One of the best experts on this subject based on the ideXlab platform.
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Femtosecond laser induced PL change in Sm-doped Sodium Borate glass and 3D optical memory
Journal of Luminescence, 2006Co-Authors: Seungphil Lee, Myeongkyu Lee, Ki-soo LimAbstract:Abstract We report on a femtosecond laser-induced photoluminescence (PL) change in Sm-doped Sodium-Borate glass and its potential application to three-dimensional optical memory. Irradiation with a femtosecond pulsed laser (800 nm, 1 kHz, 100 fs) induced a new PL peak near 682 nm, resulting from the photoreduction of Sm ions from Sm3+ to Sm2+. This makes it possible to readout the stored data by detecting the new PL peak as a signal. Multilayer patterns of various dot sizes and interlayer spacings were fabricated by femtosecond pulsed laser. These patterns were read out by a fluorescent confocal microscope which detected the emission at 682 nm as a signal. Here we discuss the feasibility of 3D optical memory by use of PL change in Sm-doped Sodium Borate glass.
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Laser-induced defect centers and valence state change of Mn ions in Sodium Borate glasses
Journal of Luminescence, 2006Co-Authors: Sunkyun Lee, Ki-soo Lim, Minh-tuan Trinh, Myeongkyu Lee, Jung-rim Nam, Eunkyoung KimAbstract:Abstract In this report, an ultrafast laser was used to produce persistent change of valence states of Mn ions in Sodium Borate glasses. Glass composition of Sodium Borate in this study was 85B 2 O 3 –15Na 2 O. We observed a broad emission at 600 nm of the transition 4 T 1 – 6 A 1 of doped Mn 2+ ions with excitation at 325 nm in an unirradiated area. Femtosecond laser irradiation produced additional strong blue emission at 440 nm and reduced the emission intensity from Mn 2+ ions. The irradiation produced the absorption band of Mn 3+ at 550 nm, resulting in color change of the glass. The blue band was measured as a function of irradiation exposure for samples with various concentrations of Mn ions. The valence state change of Mn 2+ to Mn 3+ was suppressed in Mn and Cr codoped glasses.
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Femtosecond laser-induced reduction in Eu-doped Sodium Borate glasses
Journal of Luminescence, 2006Co-Authors: Ki-soo Lim, Sunkyun Lee, Minh-tuan Trinh, Suk-ho Kim, Myeongkyu Lee, D.s. Hamilton, George N. GibsonAbstract:Abstract In this work, we report permanent reduction of Eu 3+ to Eu 2+ in Sodium Borate glasses by irradiation of near-infrared femtosecond laser. Glass composition of Sodium Borate was 85B 2 O 3 –15Na 2 O. The glasses were doped with 0.05, 0.1, and 0.5 mol% Eu 2 O 3 . Absorption and fluorescence dynamics were studied to investigate valence state change of europium ions and the energy transfer between Eu 2+ and Eu 3+ ions. As the femtosecond laser intensity or exposure time increases, the emission band at 400 nm becomes stronger. However, the photoreduction efficiency decreases as the dopant concentration increases. We discuss the photoreduction mechanism under multiphoton absorption.
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3D Optical Memory by Photoluminescence Change in Sm-doped Sodium Borate Glass
Integrated Photonics Research and Applications Nanophotonics for Information Systems, 2005Co-Authors: Myeongkyu Lee, Sunkyun Lee, Jinhyong Lim, Eunkyoung Kim, Ki-soo LimAbstract:We observed femtosecond laser-induced photoluminescence (PL) change in Sm-doped Sodium-Borate glass. Recording and readout of the multi-layer dot patterns by use of this spectral change are here discussed
