1997 Fiscal Year Final Research Report Summary
Growth of Ferroelectric Single Crystals and Applications to Optical Devices
| Project/Area Number |
08650387
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Electronic materials/Electric materials
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| Research Institution | Toyama Prefectural University |
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Principal Investigator |
CHEN Zhiming Toyama Prefectural University, Faculty of Engineering, Research Associate, 工学部, 助手 (10254236)
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| Project Period (FY) |
1996 – 1997
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| Keywords | tungsten-bronze structure / crystal growth / nonlinear optics / second harmonic generation / phase macthing / refractive index dispersion / optic absorption coefficient / electrooptic effect |
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| Research Abstract |
Tungsten-bronze type single crystals, K_3Li_2Nb_5O_<15>, were grown from melt A (0.342K_2O-0.175Li_2O-0.483Nb_2O_5) and melt B (0.348K_2O-0.187Li_2O-0.465Nb_2O_5). Compositions of crystal A and crystal B were 0.31/0.14/0.55 and 0.315/0.15/0.535, respectively, The growth rate was limited in 2-3mm/h because of its incongruence. One of the key points for the growth is to whittle down the crystal end before moving it from the melt. For crystal A,Curie point Tc=370ﾟC,electrooptic coefficient r_<33>=35pm/V.For crystal B,Tc=436ﾟC,r_<13>=8pm/V,r_<33>=66pm/V,r_<42>=87pm/V (lambda=633nm), optic absorption was smaller than 0.3/cm in 420-800nm region, nonlinear optic coefficient d_<31> was 1.3 time of that of LiNbO_3 (lambda=1064nm).
Refractive indices of Crystal B were measured, and both no and ne fitted well to Sellmeier's dispersion relations. ne increased with temperature increasing. According to the indices, the shortest wavelength for SHG is 461nm. To generate 425nm blue beam, the composition has to be changed to Nb52mol%.
The deviation of composition was investigated in a crystal weighted 15g grown from 300g-melt. Containing of Nb in bottom was about 0.5mol% more than that in neck part. It is better for SHG that the deviation of composition is less than 0.01mol% for a 6cm-long crystal. Therefore, a normal rf-heating crystal growth equipment was improved on to be continue-charged. Calcined powder could be continually charged into crucible to offset the composition change in the melt during the crystal growth. It resulted in a crystal with less deviation.
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