Abstract

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.

© 2001 Optical Society of America

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  1. D. H. Cho, K. Hirao, and N. Soga, “Persistent spectral hole burning of Sm2+ in borate glasses,” J. Non-Cryst. Solids 189, 181–190 (1995), and references therein.
    [CrossRef]
  2. R. M. Macfarlane and R. M. Shelby, “Measurement of optical dephasing of Eu3+ and Pr3+ doped silicate glasses by spectral hole-burning,” Opt. Commun. 45, 46–51 (1983).
    [CrossRef]
  3. K. Fujita, K. Tanaka, K. Hirao, and N. Soga, “Room-temperature persistent spectral hole burning of Eu3+ in sodium aluminosilicate glasses,” Opt. Lett. 23, 543–545 (1998).
    [CrossRef]
  4. K. Fujita, K. Tanaka, K. Hirao, and N. Soga, “High-temperature persistent spectral hole burning of Eu3+ ions in silicate glasses: new room-temperature hole-burning materials,” J. Opt. Soc. Am. B 15, 2700–2705 (1998).
    [CrossRef]
  5. K. Fujita, K. Tanaka, K. Yamashita, and K. Hirao, “Room-temperature persistent spectral hole burning of Eu3+-doped sodium borate glasses,” J. Lumin. 87–89, 682–684 (2000).
    [CrossRef]
  6. M. Nogami, T. Hayakawa, and T. Ishikawa, “Room-temperature photochemical hole burning in Eu3+-doped Al2O3–SiO2 glass,” Appl. Phys. Lett. 75, 3072–3075 (1999).
    [CrossRef]
  7. D. Ricard, W. Beck, A. Y. Karasik, M. A. Borik, and J. Arvanitidis, “Room-temperature persistent spectral hole burning in Eu3+-doped Inorganic glasses: the mechanisms,” J. Lumin. 86, 317–322 (2000).
    [CrossRef]
  8. J. Qiu, K. Miura, T. Suzuki, T. Mitsuyu, and K. Hirao, “Permanent photoreduction of Sm3+ to Sm2+ inside a sodium aluminoborate glass by an infrared femtosecond pulse laser,” Appl. Phys. Lett. 74, 10–12 (1999).
    [CrossRef]
  9. J. Qiu, K. Kojima, K. Mira, T. Mituyu, and K. Hirao, “Infrared femtosecond laser pulse-induced permanent reduction of Eu3+ to Eu2+ in a fluorozirconate glass,” Opt. Lett. 24, 786–788 (1999).
    [CrossRef]
  10. H. Ebendorff-Heidepriem and D. Ehrt, “Electron spin resonance spectra of Eu2+ and Tb4+ ions in glasses,” J. Phys. Condens. Matter 11, 7627–7634 (1999), and references therein.
    [CrossRef]
  11. A. Bishay, “Radiation induced color centers in multicomponent glass,” J. Non-Cryst. Solids 3, 54–114 (1970).
    [CrossRef]
  12. O. M. Efimov, K. Gabel, S. V. Garnov, L. B. Glebov, S. Grantham, M. Richardson, and M. J. Soeileau, “Color-center generation in silicate glass exposed to infrared femtosecond pulse,” J. Opt. Soc. Am B 15, 193–199 (1998).
    [CrossRef]
  13. K. Tanaka, K. Fujita, N. Matsuoka, K. Hirao, and N. Soga, “Large Faraday effect and local structure of alkali silicate glasses containing divalent europium ions,” J. Mater. Res. 13, 1989–1995 (1998).
    [CrossRef]
  14. G. M. Williams, J. A. Ruller, and E. J. Friebele, “Permanent photoinduced refractive index changes in rare earth doped glasses,” Proc. Mater. Res. Soc. Symp. 224, 59–64 (1992).

2000

D. Ricard, W. Beck, A. Y. Karasik, M. A. Borik, and J. Arvanitidis, “Room-temperature persistent spectral hole burning in Eu3+-doped Inorganic glasses: the mechanisms,” J. Lumin. 86, 317–322 (2000).
[CrossRef]

K. Fujita, K. Tanaka, K. Yamashita, and K. Hirao, “Room-temperature persistent spectral hole burning of Eu3+-doped sodium borate glasses,” J. Lumin. 87–89, 682–684 (2000).
[CrossRef]

1999

M. Nogami, T. Hayakawa, and T. Ishikawa, “Room-temperature photochemical hole burning in Eu3+-doped Al2O3–SiO2 glass,” Appl. Phys. Lett. 75, 3072–3075 (1999).
[CrossRef]

J. Qiu, K. Miura, T. Suzuki, T. Mitsuyu, and K. Hirao, “Permanent photoreduction of Sm3+ to Sm2+ inside a sodium aluminoborate glass by an infrared femtosecond pulse laser,” Appl. Phys. Lett. 74, 10–12 (1999).
[CrossRef]

J. Qiu, K. Kojima, K. Mira, T. Mituyu, and K. Hirao, “Infrared femtosecond laser pulse-induced permanent reduction of Eu3+ to Eu2+ in a fluorozirconate glass,” Opt. Lett. 24, 786–788 (1999).
[CrossRef]

H. Ebendorff-Heidepriem and D. Ehrt, “Electron spin resonance spectra of Eu2+ and Tb4+ ions in glasses,” J. Phys. Condens. Matter 11, 7627–7634 (1999), and references therein.
[CrossRef]

1998

K. Fujita, K. Tanaka, K. Hirao, and N. Soga, “Room-temperature persistent spectral hole burning of Eu3+ in sodium aluminosilicate glasses,” Opt. Lett. 23, 543–545 (1998).
[CrossRef]

K. Fujita, K. Tanaka, K. Hirao, and N. Soga, “High-temperature persistent spectral hole burning of Eu3+ ions in silicate glasses: new room-temperature hole-burning materials,” J. Opt. Soc. Am. B 15, 2700–2705 (1998).
[CrossRef]

O. M. Efimov, K. Gabel, S. V. Garnov, L. B. Glebov, S. Grantham, M. Richardson, and M. J. Soeileau, “Color-center generation in silicate glass exposed to infrared femtosecond pulse,” J. Opt. Soc. Am B 15, 193–199 (1998).
[CrossRef]

K. Tanaka, K. Fujita, N. Matsuoka, K. Hirao, and N. Soga, “Large Faraday effect and local structure of alkali silicate glasses containing divalent europium ions,” J. Mater. Res. 13, 1989–1995 (1998).
[CrossRef]

1995

D. H. Cho, K. Hirao, and N. Soga, “Persistent spectral hole burning of Sm2+ in borate glasses,” J. Non-Cryst. Solids 189, 181–190 (1995), and references therein.
[CrossRef]

1992

G. M. Williams, J. A. Ruller, and E. J. Friebele, “Permanent photoinduced refractive index changes in rare earth doped glasses,” Proc. Mater. Res. Soc. Symp. 224, 59–64 (1992).

1983

R. M. Macfarlane and R. M. Shelby, “Measurement of optical dephasing of Eu3+ and Pr3+ doped silicate glasses by spectral hole-burning,” Opt. Commun. 45, 46–51 (1983).
[CrossRef]

1970

A. Bishay, “Radiation induced color centers in multicomponent glass,” J. Non-Cryst. Solids 3, 54–114 (1970).
[CrossRef]

Arvanitidis, J.

D. Ricard, W. Beck, A. Y. Karasik, M. A. Borik, and J. Arvanitidis, “Room-temperature persistent spectral hole burning in Eu3+-doped Inorganic glasses: the mechanisms,” J. Lumin. 86, 317–322 (2000).
[CrossRef]

Beck, W.

D. Ricard, W. Beck, A. Y. Karasik, M. A. Borik, and J. Arvanitidis, “Room-temperature persistent spectral hole burning in Eu3+-doped Inorganic glasses: the mechanisms,” J. Lumin. 86, 317–322 (2000).
[CrossRef]

Bishay, A.

A. Bishay, “Radiation induced color centers in multicomponent glass,” J. Non-Cryst. Solids 3, 54–114 (1970).
[CrossRef]

Borik, M. A.

D. Ricard, W. Beck, A. Y. Karasik, M. A. Borik, and J. Arvanitidis, “Room-temperature persistent spectral hole burning in Eu3+-doped Inorganic glasses: the mechanisms,” J. Lumin. 86, 317–322 (2000).
[CrossRef]

Cho, D. H.

D. H. Cho, K. Hirao, and N. Soga, “Persistent spectral hole burning of Sm2+ in borate glasses,” J. Non-Cryst. Solids 189, 181–190 (1995), and references therein.
[CrossRef]

Ebendorff-Heidepriem, H.

H. Ebendorff-Heidepriem and D. Ehrt, “Electron spin resonance spectra of Eu2+ and Tb4+ ions in glasses,” J. Phys. Condens. Matter 11, 7627–7634 (1999), and references therein.
[CrossRef]

Efimov, O. M.

O. M. Efimov, K. Gabel, S. V. Garnov, L. B. Glebov, S. Grantham, M. Richardson, and M. J. Soeileau, “Color-center generation in silicate glass exposed to infrared femtosecond pulse,” J. Opt. Soc. Am B 15, 193–199 (1998).
[CrossRef]

Ehrt, D.

H. Ebendorff-Heidepriem and D. Ehrt, “Electron spin resonance spectra of Eu2+ and Tb4+ ions in glasses,” J. Phys. Condens. Matter 11, 7627–7634 (1999), and references therein.
[CrossRef]

Friebele, E. J.

G. M. Williams, J. A. Ruller, and E. J. Friebele, “Permanent photoinduced refractive index changes in rare earth doped glasses,” Proc. Mater. Res. Soc. Symp. 224, 59–64 (1992).

Fujita, K.

K. Fujita, K. Tanaka, K. Yamashita, and K. Hirao, “Room-temperature persistent spectral hole burning of Eu3+-doped sodium borate glasses,” J. Lumin. 87–89, 682–684 (2000).
[CrossRef]

K. Fujita, K. Tanaka, K. Hirao, and N. Soga, “High-temperature persistent spectral hole burning of Eu3+ ions in silicate glasses: new room-temperature hole-burning materials,” J. Opt. Soc. Am. B 15, 2700–2705 (1998).
[CrossRef]

K. Fujita, K. Tanaka, K. Hirao, and N. Soga, “Room-temperature persistent spectral hole burning of Eu3+ in sodium aluminosilicate glasses,” Opt. Lett. 23, 543–545 (1998).
[CrossRef]

K. Tanaka, K. Fujita, N. Matsuoka, K. Hirao, and N. Soga, “Large Faraday effect and local structure of alkali silicate glasses containing divalent europium ions,” J. Mater. Res. 13, 1989–1995 (1998).
[CrossRef]

Gabel, K.

O. M. Efimov, K. Gabel, S. V. Garnov, L. B. Glebov, S. Grantham, M. Richardson, and M. J. Soeileau, “Color-center generation in silicate glass exposed to infrared femtosecond pulse,” J. Opt. Soc. Am B 15, 193–199 (1998).
[CrossRef]

Garnov, S. V.

O. M. Efimov, K. Gabel, S. V. Garnov, L. B. Glebov, S. Grantham, M. Richardson, and M. J. Soeileau, “Color-center generation in silicate glass exposed to infrared femtosecond pulse,” J. Opt. Soc. Am B 15, 193–199 (1998).
[CrossRef]

Glebov, L. B.

O. M. Efimov, K. Gabel, S. V. Garnov, L. B. Glebov, S. Grantham, M. Richardson, and M. J. Soeileau, “Color-center generation in silicate glass exposed to infrared femtosecond pulse,” J. Opt. Soc. Am B 15, 193–199 (1998).
[CrossRef]

Grantham, S.

O. M. Efimov, K. Gabel, S. V. Garnov, L. B. Glebov, S. Grantham, M. Richardson, and M. J. Soeileau, “Color-center generation in silicate glass exposed to infrared femtosecond pulse,” J. Opt. Soc. Am B 15, 193–199 (1998).
[CrossRef]

Hayakawa, T.

M. Nogami, T. Hayakawa, and T. Ishikawa, “Room-temperature photochemical hole burning in Eu3+-doped Al2O3–SiO2 glass,” Appl. Phys. Lett. 75, 3072–3075 (1999).
[CrossRef]

Hirao, K.

K. Fujita, K. Tanaka, K. Yamashita, and K. Hirao, “Room-temperature persistent spectral hole burning of Eu3+-doped sodium borate glasses,” J. Lumin. 87–89, 682–684 (2000).
[CrossRef]

J. Qiu, K. Miura, T. Suzuki, T. Mitsuyu, and K. Hirao, “Permanent photoreduction of Sm3+ to Sm2+ inside a sodium aluminoborate glass by an infrared femtosecond pulse laser,” Appl. Phys. Lett. 74, 10–12 (1999).
[CrossRef]

J. Qiu, K. Kojima, K. Mira, T. Mituyu, and K. Hirao, “Infrared femtosecond laser pulse-induced permanent reduction of Eu3+ to Eu2+ in a fluorozirconate glass,” Opt. Lett. 24, 786–788 (1999).
[CrossRef]

K. Tanaka, K. Fujita, N. Matsuoka, K. Hirao, and N. Soga, “Large Faraday effect and local structure of alkali silicate glasses containing divalent europium ions,” J. Mater. Res. 13, 1989–1995 (1998).
[CrossRef]

K. Fujita, K. Tanaka, K. Hirao, and N. Soga, “High-temperature persistent spectral hole burning of Eu3+ ions in silicate glasses: new room-temperature hole-burning materials,” J. Opt. Soc. Am. B 15, 2700–2705 (1998).
[CrossRef]

K. Fujita, K. Tanaka, K. Hirao, and N. Soga, “Room-temperature persistent spectral hole burning of Eu3+ in sodium aluminosilicate glasses,” Opt. Lett. 23, 543–545 (1998).
[CrossRef]

D. H. Cho, K. Hirao, and N. Soga, “Persistent spectral hole burning of Sm2+ in borate glasses,” J. Non-Cryst. Solids 189, 181–190 (1995), and references therein.
[CrossRef]

Ishikawa, T.

M. Nogami, T. Hayakawa, and T. Ishikawa, “Room-temperature photochemical hole burning in Eu3+-doped Al2O3–SiO2 glass,” Appl. Phys. Lett. 75, 3072–3075 (1999).
[CrossRef]

Karasik, A. Y.

D. Ricard, W. Beck, A. Y. Karasik, M. A. Borik, and J. Arvanitidis, “Room-temperature persistent spectral hole burning in Eu3+-doped Inorganic glasses: the mechanisms,” J. Lumin. 86, 317–322 (2000).
[CrossRef]

Kojima, K.

Macfarlane, R. M.

R. M. Macfarlane and R. M. Shelby, “Measurement of optical dephasing of Eu3+ and Pr3+ doped silicate glasses by spectral hole-burning,” Opt. Commun. 45, 46–51 (1983).
[CrossRef]

Matsuoka, N.

K. Tanaka, K. Fujita, N. Matsuoka, K. Hirao, and N. Soga, “Large Faraday effect and local structure of alkali silicate glasses containing divalent europium ions,” J. Mater. Res. 13, 1989–1995 (1998).
[CrossRef]

Mira, K.

Mitsuyu, T.

J. Qiu, K. Miura, T. Suzuki, T. Mitsuyu, and K. Hirao, “Permanent photoreduction of Sm3+ to Sm2+ inside a sodium aluminoborate glass by an infrared femtosecond pulse laser,” Appl. Phys. Lett. 74, 10–12 (1999).
[CrossRef]

Mituyu, T.

Miura, K.

J. Qiu, K. Miura, T. Suzuki, T. Mitsuyu, and K. Hirao, “Permanent photoreduction of Sm3+ to Sm2+ inside a sodium aluminoborate glass by an infrared femtosecond pulse laser,” Appl. Phys. Lett. 74, 10–12 (1999).
[CrossRef]

Nogami, M.

M. Nogami, T. Hayakawa, and T. Ishikawa, “Room-temperature photochemical hole burning in Eu3+-doped Al2O3–SiO2 glass,” Appl. Phys. Lett. 75, 3072–3075 (1999).
[CrossRef]

Qiu, J.

J. Qiu, K. Miura, T. Suzuki, T. Mitsuyu, and K. Hirao, “Permanent photoreduction of Sm3+ to Sm2+ inside a sodium aluminoborate glass by an infrared femtosecond pulse laser,” Appl. Phys. Lett. 74, 10–12 (1999).
[CrossRef]

J. Qiu, K. Kojima, K. Mira, T. Mituyu, and K. Hirao, “Infrared femtosecond laser pulse-induced permanent reduction of Eu3+ to Eu2+ in a fluorozirconate glass,” Opt. Lett. 24, 786–788 (1999).
[CrossRef]

Ricard, D.

D. Ricard, W. Beck, A. Y. Karasik, M. A. Borik, and J. Arvanitidis, “Room-temperature persistent spectral hole burning in Eu3+-doped Inorganic glasses: the mechanisms,” J. Lumin. 86, 317–322 (2000).
[CrossRef]

Richardson, M.

O. M. Efimov, K. Gabel, S. V. Garnov, L. B. Glebov, S. Grantham, M. Richardson, and M. J. Soeileau, “Color-center generation in silicate glass exposed to infrared femtosecond pulse,” J. Opt. Soc. Am B 15, 193–199 (1998).
[CrossRef]

Ruller, J. A.

G. M. Williams, J. A. Ruller, and E. J. Friebele, “Permanent photoinduced refractive index changes in rare earth doped glasses,” Proc. Mater. Res. Soc. Symp. 224, 59–64 (1992).

Shelby, R. M.

R. M. Macfarlane and R. M. Shelby, “Measurement of optical dephasing of Eu3+ and Pr3+ doped silicate glasses by spectral hole-burning,” Opt. Commun. 45, 46–51 (1983).
[CrossRef]

Soeileau, M. J.

O. M. Efimov, K. Gabel, S. V. Garnov, L. B. Glebov, S. Grantham, M. Richardson, and M. J. Soeileau, “Color-center generation in silicate glass exposed to infrared femtosecond pulse,” J. Opt. Soc. Am B 15, 193–199 (1998).
[CrossRef]

Soga, N.

K. Tanaka, K. Fujita, N. Matsuoka, K. Hirao, and N. Soga, “Large Faraday effect and local structure of alkali silicate glasses containing divalent europium ions,” J. Mater. Res. 13, 1989–1995 (1998).
[CrossRef]

K. Fujita, K. Tanaka, K. Hirao, and N. Soga, “Room-temperature persistent spectral hole burning of Eu3+ in sodium aluminosilicate glasses,” Opt. Lett. 23, 543–545 (1998).
[CrossRef]

K. Fujita, K. Tanaka, K. Hirao, and N. Soga, “High-temperature persistent spectral hole burning of Eu3+ ions in silicate glasses: new room-temperature hole-burning materials,” J. Opt. Soc. Am. B 15, 2700–2705 (1998).
[CrossRef]

D. H. Cho, K. Hirao, and N. Soga, “Persistent spectral hole burning of Sm2+ in borate glasses,” J. Non-Cryst. Solids 189, 181–190 (1995), and references therein.
[CrossRef]

Suzuki, T.

J. Qiu, K. Miura, T. Suzuki, T. Mitsuyu, and K. Hirao, “Permanent photoreduction of Sm3+ to Sm2+ inside a sodium aluminoborate glass by an infrared femtosecond pulse laser,” Appl. Phys. Lett. 74, 10–12 (1999).
[CrossRef]

Tanaka, K.

K. Fujita, K. Tanaka, K. Yamashita, and K. Hirao, “Room-temperature persistent spectral hole burning of Eu3+-doped sodium borate glasses,” J. Lumin. 87–89, 682–684 (2000).
[CrossRef]

K. Fujita, K. Tanaka, K. Hirao, and N. Soga, “High-temperature persistent spectral hole burning of Eu3+ ions in silicate glasses: new room-temperature hole-burning materials,” J. Opt. Soc. Am. B 15, 2700–2705 (1998).
[CrossRef]

K. Fujita, K. Tanaka, K. Hirao, and N. Soga, “Room-temperature persistent spectral hole burning of Eu3+ in sodium aluminosilicate glasses,” Opt. Lett. 23, 543–545 (1998).
[CrossRef]

K. Tanaka, K. Fujita, N. Matsuoka, K. Hirao, and N. Soga, “Large Faraday effect and local structure of alkali silicate glasses containing divalent europium ions,” J. Mater. Res. 13, 1989–1995 (1998).
[CrossRef]

Williams, G. M.

G. M. Williams, J. A. Ruller, and E. J. Friebele, “Permanent photoinduced refractive index changes in rare earth doped glasses,” Proc. Mater. Res. Soc. Symp. 224, 59–64 (1992).

Yamashita, K.

K. Fujita, K. Tanaka, K. Yamashita, and K. Hirao, “Room-temperature persistent spectral hole burning of Eu3+-doped sodium borate glasses,” J. Lumin. 87–89, 682–684 (2000).
[CrossRef]

Appl. Phys. Lett.

M. Nogami, T. Hayakawa, and T. Ishikawa, “Room-temperature photochemical hole burning in Eu3+-doped Al2O3–SiO2 glass,” Appl. Phys. Lett. 75, 3072–3075 (1999).
[CrossRef]

J. Qiu, K. Miura, T. Suzuki, T. Mitsuyu, and K. Hirao, “Permanent photoreduction of Sm3+ to Sm2+ inside a sodium aluminoborate glass by an infrared femtosecond pulse laser,” Appl. Phys. Lett. 74, 10–12 (1999).
[CrossRef]

J. Lumin.

D. Ricard, W. Beck, A. Y. Karasik, M. A. Borik, and J. Arvanitidis, “Room-temperature persistent spectral hole burning in Eu3+-doped Inorganic glasses: the mechanisms,” J. Lumin. 86, 317–322 (2000).
[CrossRef]

K. Fujita, K. Tanaka, K. Yamashita, and K. Hirao, “Room-temperature persistent spectral hole burning of Eu3+-doped sodium borate glasses,” J. Lumin. 87–89, 682–684 (2000).
[CrossRef]

J. Mater. Res.

K. Tanaka, K. Fujita, N. Matsuoka, K. Hirao, and N. Soga, “Large Faraday effect and local structure of alkali silicate glasses containing divalent europium ions,” J. Mater. Res. 13, 1989–1995 (1998).
[CrossRef]

J. Non-Cryst. Solids

A. Bishay, “Radiation induced color centers in multicomponent glass,” J. Non-Cryst. Solids 3, 54–114 (1970).
[CrossRef]

D. H. Cho, K. Hirao, and N. Soga, “Persistent spectral hole burning of Sm2+ in borate glasses,” J. Non-Cryst. Solids 189, 181–190 (1995), and references therein.
[CrossRef]

J. Opt. Soc. Am B

O. M. Efimov, K. Gabel, S. V. Garnov, L. B. Glebov, S. Grantham, M. Richardson, and M. J. Soeileau, “Color-center generation in silicate glass exposed to infrared femtosecond pulse,” J. Opt. Soc. Am B 15, 193–199 (1998).
[CrossRef]

J. Opt. Soc. Am. B

J. Phys. Condens. Matter

H. Ebendorff-Heidepriem and D. Ehrt, “Electron spin resonance spectra of Eu2+ and Tb4+ ions in glasses,” J. Phys. Condens. Matter 11, 7627–7634 (1999), and references therein.
[CrossRef]

Opt. Commun.

R. M. Macfarlane and R. M. Shelby, “Measurement of optical dephasing of Eu3+ and Pr3+ doped silicate glasses by spectral hole-burning,” Opt. Commun. 45, 46–51 (1983).
[CrossRef]

Opt. Lett.

Proc. Mater. Res. Soc. Symp.

G. M. Williams, J. A. Ruller, and E. J. Friebele, “Permanent photoinduced refractive index changes in rare earth doped glasses,” Proc. Mater. Res. Soc. Symp. 224, 59–64 (1992).

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Figures (3)

Fig. 1
Fig. 1

Optical absorption spectra of Eu3+-doped 35Na2O·65B2O3 glass before (dotted curve) and after (solid curve) 800-nm fs laser irradiation. Inset, effectively induced absorption spectrum, obtained by subtracting the spectrum of the specimen before irradiation from that after irradiation. The measurements were carried out at room temperature.

Fig. 2
Fig. 2

(a) ESR spectrum of Eu3+-doped 35Na2O·65B2O3 glass irradiated with 800-nm fs laser pulses. (b) ESR spectrum of Eu2+-doped 35Na2O·65B2O3 glass prepared under a reducing atmosphere. The measurements were carried out at an x-band frequency at room temperature.

Fig. 3
Fig. 3

(a) Excitation spectra at 77  K before and after hole burning for Eu3+-doped 35Na2O·65B2O3·1.0Eu2O3 glass irradiated with 800-nm fs laser pulses. (b) Hole burning at 77  K and room temperature (RT). Both spectra were obtained from the difference of excitation spectra before and after dye-laser irradiation at a wavelength of 578.8  nm for 300  s.

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