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Writing of crystal line patterns in glass by laser irradiation
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Journal of Non-Crystalline Solids 354 (2008) 468–471 www.elsevier.com/locate/jnoncrysol
Writing of crystal line patterns in glass by laser irradiation Tsuyoshi Honma a, Rie Ihara a, Yasuhiko Benino a, Ryuji Sato b, Takumi Fujiwara c, Takayuki Komatsu a,* a
Department of Materials Science and Technology, Nagaoka Univeristy of Technology, Nagaoka 940-2188, Japan b Department of Materials Engineering, Tsuruoka National College of Technology, Tsuruoka 997-8511, Japan c Department of Applied Physics, Tohoku University, Aoba-ku Sendai 980-8579, Japan Available online 5 November 2007
Abstract We examined the laser-induced crystallization to form the fresnoite type Ba2TiGe2O8 crystal line patterns in transition metal ion doped BaO–TiO2–GeO2 glass. Ba2TiGe2O8 crystal line was written in 0.6FeO–33.3BaO–16.7TiO2–50GeO2 glass by continuous wave yttrium–aluminum–garnet (YAG) laser irradiation. We obtained polarization dependence of Raman spectra in crystal line pattern. Second harmonic generation (SHG) indicated unique fringe patterns from Ba2TiGe2O8 crystal lines. 2007 Elsevier B.V. All rights reserved. PACS: 42.65.Ky; 42.70.Nq; 81.05.Kf; 81.05.Pj Keywords: Crystal growth; Ferroelectric; Laser–matter interactions; Optical microscopy; Lasers; Nonlinear optics; Raman spectroscopy; Borates; Germanates
1. Introduction Laser irradiation to glass has been regarded as a process for spatially selected structural modification and/or crystallization in glass [1,2]. The present authors’ group [3–7] has proposed that the irradiation of a cw Nd:YAG laser with k = 1064 nm induces the formation of dot/line shape crystallite in Sm3+ and Dy3+ containing oxide glasses. The laser-induced crystallization behavior in samarium ion heat processing with the use of fundamental wavelength of YAG laser (k = 1064 nm) is examined by Sato et al. [3]. They confirmed the formation of Sm2Te6O15 micro-crystalline dots on 10Sm2O3–10BaO–80TeO2 glass and proposed the crystallization mechanism as follows: Since Sm3+ has an absorption band around 1064 nm, some energy of cw Nd:YAG laser is absorbed by Sm3+ in glass through f–f transitions (6F9/2 ! 6H5/2), consequently inducing thermal effects through continuous electron–phonon coupling. We
*
Corresponding author. Tel.: +81 258 47 9313; fax: +81 258 47 9300. E-mail address: [email protected] (T. Komatsu).
0022-3093/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2007.07.081
found the same behavior in dysprosium (Dy3+) ion containing glasses [4]. This technique for the writing of crystal dots and lines in glasses might be, therefore, called ‘Rareearth ion heat processing’ (REIH). By using REIH technique, present authors have succeeded in patterning of single crystal lines consisting of b-BaB2O4 (designated as b-BBO) nonlinear optical crystals in some glasses [4]. Ihara et al. [5] have reported the writing of two-dimensional crystal curved or bending lines consisting of rare-earth ion doped BiBO3 crystals showing a second harmonic generation (SHG). Recently, Gupta et al. [8] fabricated Nd0.2La0.8BGeO5 crystallites by the irradiation of titanium-sapphire light source of wavelength k = 800 nm to Nd2O3–La2O3–B2O3–GeO2 glass. Nd3+ has the absorption band around 800 nm and shows the non-radiative relaxation inducing thermal effects. Furthermore, the present authors’ group proposed a transition metal ion (such as V3+, V4+, Fe2+, Ni2+, Cu2+) heat processing technique (TMIH), instead of REIH processing [9]. The doping amount of transition metal ions for inducing crystallization in glass is small compared to rare-earth ions such as Sm3+ and Dy3+.
T. Honma et al. / Journal of Non-Crystalline Solids 354 (2008) 468–471
In this paper, we examined the writing of crystal line patterning consisting of Ba2TiGe2O8 (BTG) optical nonlinear crystal in BaO–TiO2–GeO2 glass TMIH processing. Second ordered optical nonlinearity of BTG crystal is examined by Takahashi et al. [10] They fabricated transparent surface crystallized glasses consisting of BTG crystals and found that they show large second order optical nonlinearity (deff 22 pm/V) comparable to that of LiNbO3 single crystal. We discuss about the morphology and second harmonic generation of BTG crystal lines compared with b-BBO crystal line [4,6,7].
469
1064 nm
Sample
Stage IR cut filter
532 nm
2. Experimental procedure
3. Results Fig. 2 shows the optical absorption spectra at room temperature for 0.6FeO–BTG50 glasses. The absorption coefficients, a, at 1064 nm has a value of 6.3 cm1 for 0.6FeO–BTG50 glass. This value is much higher than a value of 4.5 cm1 for 10Sm2O3–40BaO–50B2O3 glass. Fig. 3 shows the polarized optical micrographs of crystallized line fabricated by cw YAG laser irradiation (power: 1.0 W, scanning speed: 7 lm/s) in 0.6FeO–BTG50 glass. The structural modifications with a width of approximately 2 lm are observed. We carried out the polarized microRaman scattering measurements to obtain the information of orientation in the crystallized pattern, and the results are
PMT/CCD camera
90˚, 270˚
ω
0˚, 180˚
ω Fig. 1. Configurations of sample and incident laser for azimuthal dependences of SH intensity by second harmonic microscope. We decided the azimuth of 0 (180) which polarization of fundamental wave (x) is normal to the scanning direction.
20
Absorption coefficients (cm -1)
The composition of the glasses examined in this study is 0.6FeO–33.3BaO–16.7TiO2–50GeO2 (0.6FeO–BTG50 glass) and prepared by a conventional melt quenching method. The glass transition, Tg, and crystallization onset, Tx, temperatures were determined using differential thermal analysis (DTA) at a heating rate of 10 K/min. The glasses were mechanically polished to a mirror finish with ceria powders. In TMIH technique a continuous wave Nd:YAG laser with k = 1064 nm irradiated the surface of the glass using an objective lens (60·). The glasses were moved at the speeds of 7 lm/s. Micro-Raman scattering spectra of fresnoite crystal lines were measured with a three-dimensional spatially resolved laser microscope (Tokyo Instruments Co. Nanofinder) operated at Ar+ (k = 488 nm) laser. In detail of the measurement of Raman spectra is described elsewhere [6,7]. To investigate the polarization dependence of second harmonic intensity from crystal lines, we established the second harmonic microscope technique, and the configuration of sample and incident laser is illustrated in Fig. 1. The second harmonic intensity of crystal lines was measured by using a fundamental wave of Q-switched Nd:YAG laser with k = 1064 nm as a laser source, in which linearly polarized fundamental laser beams were introduced into crystal lines perpendicularly and the azimuthal dependence of SHG signals was measured by rotating the sample with the analyzer parallel to the polarized direction of a normally incident fundamental beam.
Polarizer
15
α (1064nm) =6.3 cm-1 10
5
0
500
1000
1500
2000
Wavelength (nm) Fig. 2. Optical absorption spectra at room temperature for the 0.6FeO– BTG50 glass.
shown in Fig. 4. We also indicated the spectra for b-BBO crystal line in Fig. 4. The sharp peaks are obtained in both cases and all peaks correspond to the b-BBO and BTG crystalline phase. In measurements of polarized Raman scattering spectra, various configurations about the
470
T. Honma et al. / Journal of Non-Crystalline Solids 354 (2008) 468–471
View from induced direction
Intensity (arb. units)
Scanning direction
y(zz)y y(xx)y
400
View from cross section
600
800
1000
Raman shift (cm-1)
Intensity (arb. units)
y(zz)y y(xx)y
Fig. 3. Polarized optical micrograph of crystal line written by Nd:YAG laser irradiation in 0.6FeO–BTG50 glass. The laser power was 1.0 W and the scanning speed was 7 lm/s.
relationship between the direction of linearly polarized incident laser and the direction of linearly polarized Raman scattering light are possible. As shown in Fig. 4(a), the Raman peaks depend strongly on the configuration. We found that the polarized micro-Raman spectra for b-BBO crystal lines are almost the same as those for y-cut single crystal. On the other hand, the peaks around 721, 798, 840 and 870 cm1 show the drastic changes between yðzzÞy and yðxxÞy configurations in the BTG crystal line as shown in Fig. 4(b). Fig. 5 shows the azimuthal dependences of SHG signals for b-BBO and BTG crystal lines. As shown in Fig. 5(a), the maximum intensities are observed at the rotation angles of 0 and 180 and the zero intensities are observed at 90 and 270, i.e., twofold angular dependences was obtained for a rotation. Meanwhile, the azimuthal dependence of BTG crystal line patterns shown in Fig. 5(b) represents the quite different profile compare to the b-BBO. The maximum intensities are observed at around 45, 135, 225 and 315, the zero intensity is found at 0 and 180, and the weak intensity shows at 90 and 270. This profile also, therefore, represents the twofold angular dependence for a rotation. 4. Discussion We confirmed the laser-induced crystallization in both of 7Sm–BaBO and 0.6FeO–BTG50 glasses with same con-
400
600
800
1000
Raman shift (cm-1) Fig. 4. Polarization optical micro-Raman scattering spectra for the (a) bBBO and (b) BTG crystal lines in glass. The configuration yðxxÞy means the polarized direction of incident beam is normal to the growth (scanning) direction of crystal line and yðzzÞy means the polarization of incident beam is parallel to the growth direction.
dition of laser irradiation. A key point in REIH processing is a combination of rare-earth ions and cw Nd:YAG laser with k = 1064 nm, and it is prerequisite to prepare glasses with low glass transition and some amounts (10 mol%) of Sm2O3, meaning some limitations of the application of REIH processing for the writing of crystal lines in glass. It is well known that transition metal ions such as V4+, Fe2+ and Ni2+ in glass give rise to absorption bands in the visible and near infrared spectral regions. The absorption bands around 1000 nm are attributed to the presence of Fe2+ ions [9]. A glass with the composition of 10Sm2O3–40BaO–50B2O3 glass has the values of glass transition (Tg) of 570 C and crystallization (Tx) of 702 C. Meanwhile 0.6FeO–BTG50 glass has the values of Tg = 670 C and Tx = 780 C. We could not confirm any photo-induced phenomena such as photo-darkening phenomena for chalcogenide glass in REIH and TMIH techniques. It is, therefore, considered that the efficiency of non-radiative relaxation in Fe2+ containing glass is much
T. Honma et al. / Journal of Non-Crystalline Solids 354 (2008) 468–471
471
Intensity (arb. units)
The solid line in Fig. 5(a) represents the fitted curve. It can be seen that the observed SH intensity maxima and minima resemble the theoretical prediction. BTG crystal line indicated a unique fringe pattern for a rotation as shown in Fig. 4(b). There has been no report on the second order optical nonlinearity of BTG single crystal. However, Bechthold et al. [12] reported the second harmonic generation in Ba2TiSi2O8 single crystal. We are now investigating the second order optical nonlinearity of BTG crystal line patterns from the results obtained by polarization Raman and second harmonic generations. At this moment, it is strongly emphasized that BTG crystal lines are highly oriented along the laser scanning direction. 0
60
120
180
240
300
360
Rotation angle (deg.)
5. Conclusion
Intensity (arb. units)
We examined the writing of Ba2TiGe2O8 crystal lines on the glass by YAG laser irradiation. We proposed that nonlinear optical BTG crystals in these lines are highly oriented (just like single crystal) along the laser scanning direction. The laser-induced ion heat processing will be widely applicable to other glass systems. Acknowledgments
0
60
120
180
240
300
360
Rotation angle (deg.) Fig. 5. The azimuthal dependence of SH intensity (a) b-BBO and (b) BTG crystal line in glass.
higher than rare-earth (Sm3+, Dy3+) ion containing glass. The other transition metal ions are also effective to introduce local heating because we also confirmed laser-induced crystallizations in glass with small addition of Ni2+, V3+, V4+ and Cu2+ by YAG laser irradiation [9]. b-BBO is one of the important nonlinear optical crystals for laser optics such as harmonic generators because of large second order nonlinear optical coefficients (d22 2 pm/V) and wide transmission (190–3500 nm). The presence of [B3O6]3 anionic hexagonal groupings slightly distorted with a threefold axis which stacked along the c-axis is the origin of their optical nonlinearity. On the other hand, BTG has a fresnoite (Ba2TiSi2O8 and Sr2TiSi2O8) type structure and is composed of a TiO5 unit which lies along c-axis, and it is considered that TiO5 unit is responsible for second order optical nonlinearity [11]. Fresnoite-type crystals are known to show good pyroelectric and piezoelectric properties. It is clear that the growth direction of b-BBO crystallized patterns is the c-axis along the scanning direction by polarization Raman scattering spectra and XRD measurements, and the effective second order nonlinear coefficient, deff, is simply given by the deff = d22 cos2 h.
This work was partially supported by the SCOPE (Strategic Information and Communications R&D Promition Program) project by the Ministry of Public Management, Home affairs, Posts and Telecommunications, Japan, the Grant-in-Aid for Scientific Research from the Ministry of Education, Science, Sport and Culture, Japan, the research collaboration with Asahi Glass Co. Ltd., and the 21st century Center of Excellence (COE) Program in Nagaoka Univerisity of Technology. References [1] M. Nogami, A. Ohno, H. You, Phys. Rev. B 68 (2003) 104204. [2] Y. Yonesaki, K. Miura, R. Araki, K. Fujita, K. Hirao, J. Non-Cryst. Solids 351 (2005) 885. [3] R. Sato, Y. Benino, T. Fujiwara, T. Komatsu, J. Non-Cryst. Solids 289 (2001) 228. [4] T. Honma, Y. Benino, R. Sato, T. Fujiwara, T. Komatsu, Appl. Phys. Lett. 83 (2003) 2796. [5] R. Ihara, T. Honma, Y. Benino, T. Fujiwara, R. Sato, T. Komatsu, Solid State Commun. 136 (2005) 273. [6] T. Honma, Y. Benino, T. Fujiwara, R. Sato, T. Komatsu, J. NonCryst. Solids 345&346 (2004) 127. [7] T. Honma, Y. Benino, R. Sato, T. Fujiwara, T. Komatsu, J. Phys. Chem. Solids 65 (2004) 1705. [8] P. Gupta, H. Jain, D.B. Williams, J. Toulouse, I. Veltchev, Opt. Mater. 29 (2006) 355. [9] T. Honma, Y. Benino, T. Fujiwara, T. Komatsu, Appl. Phys. Lett. 88 (2006) 231105. [10] Y. Takahashi, Y. Benino, T. Fujiwara, T. Komatsu, Appl. Phys. Lett. 81 (2002) 223. [11] T. Hoche, S. Esmaeilzadeh, R. Uecker, S. lidin, W. Neumann, Acta Crystallogr. B 59 (2003) 209. [12] P.S. Bechthold, S. Haussu¨hl, E. Michael, J. Eckstein, K. Recker, F. Wallrafen, Phys. Lett. A 65 (1978) 453.
Journal of Non-Crystalline Solids 354 (2008) 468–471 www.elsevier.com/locate/jnoncrysol
Writing of crystal line patterns in glass by laser irradiation Tsuyoshi Honma a, Rie Ihara a, Yasuhiko Benino a, Ryuji Sato b, Takumi Fujiwara c, Takayuki Komatsu a,* a
Department of Materials Science and Technology, Nagaoka Univeristy of Technology, Nagaoka 940-2188, Japan b Department of Materials Engineering, Tsuruoka National College of Technology, Tsuruoka 997-8511, Japan c Department of Applied Physics, Tohoku University, Aoba-ku Sendai 980-8579, Japan Available online 5 November 2007
Abstract We examined the laser-induced crystallization to form the fresnoite type Ba2TiGe2O8 crystal line patterns in transition metal ion doped BaO–TiO2–GeO2 glass. Ba2TiGe2O8 crystal line was written in 0.6FeO–33.3BaO–16.7TiO2–50GeO2 glass by continuous wave yttrium–aluminum–garnet (YAG) laser irradiation. We obtained polarization dependence of Raman spectra in crystal line pattern. Second harmonic generation (SHG) indicated unique fringe patterns from Ba2TiGe2O8 crystal lines. 2007 Elsevier B.V. All rights reserved. PACS: 42.65.Ky; 42.70.Nq; 81.05.Kf; 81.05.Pj Keywords: Crystal growth; Ferroelectric; Laser–matter interactions; Optical microscopy; Lasers; Nonlinear optics; Raman spectroscopy; Borates; Germanates
1. Introduction Laser irradiation to glass has been regarded as a process for spatially selected structural modification and/or crystallization in glass [1,2]. The present authors’ group [3–7] has proposed that the irradiation of a cw Nd:YAG laser with k = 1064 nm induces the formation of dot/line shape crystallite in Sm3+ and Dy3+ containing oxide glasses. The laser-induced crystallization behavior in samarium ion heat processing with the use of fundamental wavelength of YAG laser (k = 1064 nm) is examined by Sato et al. [3]. They confirmed the formation of Sm2Te6O15 micro-crystalline dots on 10Sm2O3–10BaO–80TeO2 glass and proposed the crystallization mechanism as follows: Since Sm3+ has an absorption band around 1064 nm, some energy of cw Nd:YAG laser is absorbed by Sm3+ in glass through f–f transitions (6F9/2 ! 6H5/2), consequently inducing thermal effects through continuous electron–phonon coupling. We
*
Corresponding author. Tel.: +81 258 47 9313; fax: +81 258 47 9300. E-mail address: [email protected] (T. Komatsu).
0022-3093/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2007.07.081
found the same behavior in dysprosium (Dy3+) ion containing glasses [4]. This technique for the writing of crystal dots and lines in glasses might be, therefore, called ‘Rareearth ion heat processing’ (REIH). By using REIH technique, present authors have succeeded in patterning of single crystal lines consisting of b-BaB2O4 (designated as b-BBO) nonlinear optical crystals in some glasses [4]. Ihara et al. [5] have reported the writing of two-dimensional crystal curved or bending lines consisting of rare-earth ion doped BiBO3 crystals showing a second harmonic generation (SHG). Recently, Gupta et al. [8] fabricated Nd0.2La0.8BGeO5 crystallites by the irradiation of titanium-sapphire light source of wavelength k = 800 nm to Nd2O3–La2O3–B2O3–GeO2 glass. Nd3+ has the absorption band around 800 nm and shows the non-radiative relaxation inducing thermal effects. Furthermore, the present authors’ group proposed a transition metal ion (such as V3+, V4+, Fe2+, Ni2+, Cu2+) heat processing technique (TMIH), instead of REIH processing [9]. The doping amount of transition metal ions for inducing crystallization in glass is small compared to rare-earth ions such as Sm3+ and Dy3+.
T. Honma et al. / Journal of Non-Crystalline Solids 354 (2008) 468–471
In this paper, we examined the writing of crystal line patterning consisting of Ba2TiGe2O8 (BTG) optical nonlinear crystal in BaO–TiO2–GeO2 glass TMIH processing. Second ordered optical nonlinearity of BTG crystal is examined by Takahashi et al. [10] They fabricated transparent surface crystallized glasses consisting of BTG crystals and found that they show large second order optical nonlinearity (deff 22 pm/V) comparable to that of LiNbO3 single crystal. We discuss about the morphology and second harmonic generation of BTG crystal lines compared with b-BBO crystal line [4,6,7].
469
1064 nm
Sample
Stage IR cut filter
532 nm
2. Experimental procedure
3. Results Fig. 2 shows the optical absorption spectra at room temperature for 0.6FeO–BTG50 glasses. The absorption coefficients, a, at 1064 nm has a value of 6.3 cm1 for 0.6FeO–BTG50 glass. This value is much higher than a value of 4.5 cm1 for 10Sm2O3–40BaO–50B2O3 glass. Fig. 3 shows the polarized optical micrographs of crystallized line fabricated by cw YAG laser irradiation (power: 1.0 W, scanning speed: 7 lm/s) in 0.6FeO–BTG50 glass. The structural modifications with a width of approximately 2 lm are observed. We carried out the polarized microRaman scattering measurements to obtain the information of orientation in the crystallized pattern, and the results are
PMT/CCD camera
90˚, 270˚
ω
0˚, 180˚
ω Fig. 1. Configurations of sample and incident laser for azimuthal dependences of SH intensity by second harmonic microscope. We decided the azimuth of 0 (180) which polarization of fundamental wave (x) is normal to the scanning direction.
20
Absorption coefficients (cm -1)
The composition of the glasses examined in this study is 0.6FeO–33.3BaO–16.7TiO2–50GeO2 (0.6FeO–BTG50 glass) and prepared by a conventional melt quenching method. The glass transition, Tg, and crystallization onset, Tx, temperatures were determined using differential thermal analysis (DTA) at a heating rate of 10 K/min. The glasses were mechanically polished to a mirror finish with ceria powders. In TMIH technique a continuous wave Nd:YAG laser with k = 1064 nm irradiated the surface of the glass using an objective lens (60·). The glasses were moved at the speeds of 7 lm/s. Micro-Raman scattering spectra of fresnoite crystal lines were measured with a three-dimensional spatially resolved laser microscope (Tokyo Instruments Co. Nanofinder) operated at Ar+ (k = 488 nm) laser. In detail of the measurement of Raman spectra is described elsewhere [6,7]. To investigate the polarization dependence of second harmonic intensity from crystal lines, we established the second harmonic microscope technique, and the configuration of sample and incident laser is illustrated in Fig. 1. The second harmonic intensity of crystal lines was measured by using a fundamental wave of Q-switched Nd:YAG laser with k = 1064 nm as a laser source, in which linearly polarized fundamental laser beams were introduced into crystal lines perpendicularly and the azimuthal dependence of SHG signals was measured by rotating the sample with the analyzer parallel to the polarized direction of a normally incident fundamental beam.
Polarizer
15
α (1064nm) =6.3 cm-1 10
5
0
500
1000
1500
2000
Wavelength (nm) Fig. 2. Optical absorption spectra at room temperature for the 0.6FeO– BTG50 glass.
shown in Fig. 4. We also indicated the spectra for b-BBO crystal line in Fig. 4. The sharp peaks are obtained in both cases and all peaks correspond to the b-BBO and BTG crystalline phase. In measurements of polarized Raman scattering spectra, various configurations about the
470
T. Honma et al. / Journal of Non-Crystalline Solids 354 (2008) 468–471
View from induced direction
Intensity (arb. units)
Scanning direction
y(zz)y y(xx)y
400
View from cross section
600
800
1000
Raman shift (cm-1)
Intensity (arb. units)
y(zz)y y(xx)y
Fig. 3. Polarized optical micrograph of crystal line written by Nd:YAG laser irradiation in 0.6FeO–BTG50 glass. The laser power was 1.0 W and the scanning speed was 7 lm/s.
relationship between the direction of linearly polarized incident laser and the direction of linearly polarized Raman scattering light are possible. As shown in Fig. 4(a), the Raman peaks depend strongly on the configuration. We found that the polarized micro-Raman spectra for b-BBO crystal lines are almost the same as those for y-cut single crystal. On the other hand, the peaks around 721, 798, 840 and 870 cm1 show the drastic changes between yðzzÞy and yðxxÞy configurations in the BTG crystal line as shown in Fig. 4(b). Fig. 5 shows the azimuthal dependences of SHG signals for b-BBO and BTG crystal lines. As shown in Fig. 5(a), the maximum intensities are observed at the rotation angles of 0 and 180 and the zero intensities are observed at 90 and 270, i.e., twofold angular dependences was obtained for a rotation. Meanwhile, the azimuthal dependence of BTG crystal line patterns shown in Fig. 5(b) represents the quite different profile compare to the b-BBO. The maximum intensities are observed at around 45, 135, 225 and 315, the zero intensity is found at 0 and 180, and the weak intensity shows at 90 and 270. This profile also, therefore, represents the twofold angular dependence for a rotation. 4. Discussion We confirmed the laser-induced crystallization in both of 7Sm–BaBO and 0.6FeO–BTG50 glasses with same con-
400
600
800
1000
Raman shift (cm-1) Fig. 4. Polarization optical micro-Raman scattering spectra for the (a) bBBO and (b) BTG crystal lines in glass. The configuration yðxxÞy means the polarized direction of incident beam is normal to the growth (scanning) direction of crystal line and yðzzÞy means the polarization of incident beam is parallel to the growth direction.
dition of laser irradiation. A key point in REIH processing is a combination of rare-earth ions and cw Nd:YAG laser with k = 1064 nm, and it is prerequisite to prepare glasses with low glass transition and some amounts (10 mol%) of Sm2O3, meaning some limitations of the application of REIH processing for the writing of crystal lines in glass. It is well known that transition metal ions such as V4+, Fe2+ and Ni2+ in glass give rise to absorption bands in the visible and near infrared spectral regions. The absorption bands around 1000 nm are attributed to the presence of Fe2+ ions [9]. A glass with the composition of 10Sm2O3–40BaO–50B2O3 glass has the values of glass transition (Tg) of 570 C and crystallization (Tx) of 702 C. Meanwhile 0.6FeO–BTG50 glass has the values of Tg = 670 C and Tx = 780 C. We could not confirm any photo-induced phenomena such as photo-darkening phenomena for chalcogenide glass in REIH and TMIH techniques. It is, therefore, considered that the efficiency of non-radiative relaxation in Fe2+ containing glass is much
T. Honma et al. / Journal of Non-Crystalline Solids 354 (2008) 468–471
471
Intensity (arb. units)
The solid line in Fig. 5(a) represents the fitted curve. It can be seen that the observed SH intensity maxima and minima resemble the theoretical prediction. BTG crystal line indicated a unique fringe pattern for a rotation as shown in Fig. 4(b). There has been no report on the second order optical nonlinearity of BTG single crystal. However, Bechthold et al. [12] reported the second harmonic generation in Ba2TiSi2O8 single crystal. We are now investigating the second order optical nonlinearity of BTG crystal line patterns from the results obtained by polarization Raman and second harmonic generations. At this moment, it is strongly emphasized that BTG crystal lines are highly oriented along the laser scanning direction. 0
60
120
180
240
300
360
Rotation angle (deg.)
5. Conclusion
Intensity (arb. units)
We examined the writing of Ba2TiGe2O8 crystal lines on the glass by YAG laser irradiation. We proposed that nonlinear optical BTG crystals in these lines are highly oriented (just like single crystal) along the laser scanning direction. The laser-induced ion heat processing will be widely applicable to other glass systems. Acknowledgments
0
60
120
180
240
300
360
Rotation angle (deg.) Fig. 5. The azimuthal dependence of SH intensity (a) b-BBO and (b) BTG crystal line in glass.
higher than rare-earth (Sm3+, Dy3+) ion containing glass. The other transition metal ions are also effective to introduce local heating because we also confirmed laser-induced crystallizations in glass with small addition of Ni2+, V3+, V4+ and Cu2+ by YAG laser irradiation [9]. b-BBO is one of the important nonlinear optical crystals for laser optics such as harmonic generators because of large second order nonlinear optical coefficients (d22 2 pm/V) and wide transmission (190–3500 nm). The presence of [B3O6]3 anionic hexagonal groupings slightly distorted with a threefold axis which stacked along the c-axis is the origin of their optical nonlinearity. On the other hand, BTG has a fresnoite (Ba2TiSi2O8 and Sr2TiSi2O8) type structure and is composed of a TiO5 unit which lies along c-axis, and it is considered that TiO5 unit is responsible for second order optical nonlinearity [11]. Fresnoite-type crystals are known to show good pyroelectric and piezoelectric properties. It is clear that the growth direction of b-BBO crystallized patterns is the c-axis along the scanning direction by polarization Raman scattering spectra and XRD measurements, and the effective second order nonlinear coefficient, deff, is simply given by the deff = d22 cos2 h.
This work was partially supported by the SCOPE (Strategic Information and Communications R&D Promition Program) project by the Ministry of Public Management, Home affairs, Posts and Telecommunications, Japan, the Grant-in-Aid for Scientific Research from the Ministry of Education, Science, Sport and Culture, Japan, the research collaboration with Asahi Glass Co. Ltd., and the 21st century Center of Excellence (COE) Program in Nagaoka Univerisity of Technology. References [1] M. Nogami, A. Ohno, H. You, Phys. Rev. B 68 (2003) 104204. [2] Y. Yonesaki, K. Miura, R. Araki, K. Fujita, K. Hirao, J. Non-Cryst. Solids 351 (2005) 885. [3] R. Sato, Y. Benino, T. Fujiwara, T. Komatsu, J. Non-Cryst. Solids 289 (2001) 228. [4] T. Honma, Y. Benino, R. Sato, T. Fujiwara, T. Komatsu, Appl. Phys. Lett. 83 (2003) 2796. [5] R. Ihara, T. Honma, Y. Benino, T. Fujiwara, R. Sato, T. Komatsu, Solid State Commun. 136 (2005) 273. [6] T. Honma, Y. Benino, T. Fujiwara, R. Sato, T. Komatsu, J. NonCryst. Solids 345&346 (2004) 127. [7] T. Honma, Y. Benino, R. Sato, T. Fujiwara, T. Komatsu, J. Phys. Chem. Solids 65 (2004) 1705. [8] P. Gupta, H. Jain, D.B. Williams, J. Toulouse, I. Veltchev, Opt. Mater. 29 (2006) 355. [9] T. Honma, Y. Benino, T. Fujiwara, T. Komatsu, Appl. Phys. Lett. 88 (2006) 231105. [10] Y. Takahashi, Y. Benino, T. Fujiwara, T. Komatsu, Appl. Phys. Lett. 81 (2002) 223. [11] T. Hoche, S. Esmaeilzadeh, R. Uecker, S. lidin, W. Neumann, Acta Crystallogr. B 59 (2003) 209. [12] P.S. Bechthold, S. Haussu¨hl, E. Michael, J. Eckstein, K. Recker, F. Wallrafen, Phys. Lett. A 65 (1978) 453.