42 1 Fig. 2. Li 2 B 4 O 7 crystals with 3inches and 4inches in diameter. Fig. 4. Transmission curve of Li 2 B 4 O 7 crystal. Fig. 5. Refractive index

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あきおやまのかみしゃ
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1 MEMOIRS OF SHONAN INSTITUTE OF TECHNOLOGY Vol. 42, No. 1, 2008 Li 2 B 4 O 7 (LBO) *, ** * ** ** Optical Scatterer and Crystal Growth Technology of LBO Single Crystal For Development with Optical Application Takahiro KOJIMA*, **, Noriaki TSUTSUI*, Suzuka NISHIMURA** and Kazutaka TERASHIMA** Li 2 B 4 O 7 (LBO) crystal is one of the piezo-electric crystals and it is used for surface acoustic wave (SAW) devices. Generally, large size scale crystals up to 4 inches in diameter with 25 inches length are obtained by the vertical Bridgman method, though optical scattering particles are included. As an optical crystal, optical scattering free crystals are much required. We found the growth method of controlling the density of scattering particles. It has been found that the crystal quality widely varied depending on the ambient gas during the growth process. The correlation of the oxygen partial pressure and the scattering particles in the crystals has been studied. Moreover, the crystal quality and the optical uniformity is discussed. 1 Li 2 B 4 O 7 LBO (Surface Acoustic Wave: SAW) 1) Filter SAW Filter LAN PHS TV GPS ETC LiTaO 3 LiNbO 3 LBO PHS SAW Fig. 1 LiTaO 3 LiNbO 3 LBO 2),3) LBO 4) Fig. 2 LBO (b-bab 2 O 4, CsB 3 O 5, CsLiB 6 O 10 ) 5) * ** Fundamental properties of SAW grade crys- Fig. 1. tals. 53

$Fig. 5. Refractive index of Li 2 B 4 O 7 crystal. Fig. 3. Scattering light of Green laser beam passing.$ Fig. 3 5) MHz GHz SAW Filter (void) LBO 6) YAG : Nd 4, 5 LBO Fig. 4 Fig.

Fig. 3 5) MHz GHz SAW Filter (void) LBO 6) YAG : Nd 4, 5 LBO Fig. 4 Fig.

2 42 1 Fig. 2. Li 2 B 4 O 7 crystals with 3inches and 4inches in diameter. Fig. 4. Transmission curve of Li 2 B 4 O 7 crystal. Fig. 5. Refractive index of Li 2 B 4 O 7 crystal. Fig. 3. Scattering light of Green laser beam passing. Fig. 3 5) MHz GHz SAW Filter (void) LBO 6) YAG : Nd 4, 5 LBO Fig. 4 Fig. 5 SAW 7) 8) SAW Grade Optical: OPT Grade (Quadrupole Mass Spectrometer: QMS) 2 LBO LBO 4mm a 9.475Å, c Å 917 C 54

Li 2 B 4 O 7 (LBO) Table 1. Structure Material parameters. Tetragonal Lattice parameters a 9.475Å b 9.475Å c 10.283Å Density 2.45 g/cm 3 Specific heat 0.68 Cal/K cm 3 Heat conductivity 0.

3 Li 2 B 4 O 7 (LBO) Table 1. Structure Material parameters. Tetragonal Lattice parameters a 9.475Å b 9.475Å c Å Density 2.45 g/cm 3 Specific heat 0.68 Cal/K cm 3 Heat conductivity W/cm K Pyro. Const C/m 2 K Melting point (congruent) 917 C Hardness 6 Fig. 7. Schematic view of vertical Bridgman. Fig. 6. Thermal expansion coefficient of Li 2 B 4 O 7 crystal g/cm 3 6 LBO Table C 280 mpas J cm 1 K 1 s C K K LBO Fig mm 20 mm mm/h C/cm Fig. 7 4 (SAW grade) (OPT grade) (110) SAW 4.1 CCD 532 nm 10 mm Green Fig. 8 55

42 1 Fig. 8. Observation method of scattering particles.

Infrared Fig. 9. Scattering particle image from SAW grade substrate.

4 42 1 Fig. 8. Observation method of scattering particles. SAW grade OPT grade Fig. 9 Fig. 10 SAW grade OPT grade nm 170 nm nm % Fig OH 5) b-bab 2 O 4, CsB 3 O 5, CsLiB 6 O 10 (Fourier-Transform Infrared Fig. 9. Scattering particle image from SAW grade substrate. Fig. 10. Scattering particle image from OPT grade substrate. Spectrometer: FT-IR) OH (Quadrupole Mass Spectrometer: QMS) SAW grade OPT grade 56

5 Li 2 B 4 O 7 (LBO) 6N Ar l/min 2 Fig. 12 OH 7 8 OPT grade Fig %, 5%, 0%, 15%, 20% Fig. 11. Transmittance of LBO crystals. Fig. 13. Result of QMS measurement. Fig. 12. Schematic view of QMS. 57

42 1 1 Ingot Table 2 (001) Fig. 14 Table 2. Growth conditions. Diameter f50 mm Angle (110) Growth rate 0.

6 Ingot Table 2 (001) Fig. 14 Table 2. Growth conditions. Diameter f50 mm Angle (110) Growth rate 0.3 mm/h OPT grade Seed f50 mm 20 mm Crucible Pt O 2 partial pressure 0 20% 15% 4.5 OPT grade B 4 3 B Fig. 15 Fig. 14. Observation photography of scattering particles. 58

Li 2 B 4 O 7 (LBO) Fig. 15. A tentative model for generation of scattering particles. 5 LBO LBO LBO 1) R. W. Whatmore, N. W. Shorrocks, C. O Hara, F. W. Ainger, and I. W. Young: Electron. Lett.

7 Li 2 B 4 O 7 (LBO) Fig. 15. A tentative model for generation of scattering particles. 5 LBO LBO LBO 1) R. W. Whatmore, N. W. Shorrocks, C. O Hara, F. W. Ainger, and I. W. Young: Electron. Lett. 17 (1981) 11. 2) p ) p ) N. Tsutsui, Y. Ino, K. Imai, N. Senguttuvan, M. Ishii: Journal of Crystal Growth 211 (2000) ) : p ) R. Komatsu, T. Sugawara, K. Sasa, N. Sarukawa, Z. Liu, S. Izumida, Y. Segawa, S. Uda, T. Fukuda, and K. Yamanouchi: Appl. Phys. Lett. 70 (1997) ) T. Sugawara, R. Komatsu, S.Uda: Journal of Crystal Growth 204 (1999) ) p

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