臺灣博碩士論文加值系統

有機非線性光學材料因高度之光非線性及合成方法的多樣化，極具發
展潛力。而其應用上晶體品質則至為重要。晶體品質主要決定於生長環境
與雜質離析。吾人以透明之垂直式動態梯度凝固$($簡稱VDGF$)$長晶爐，
生長非線性光學材料苯偶醯$($Benzil$)$，透過電腦自動控制、記錄、可
視化的觀察與晶體後續之摻雜濃度量測、二倍頻效應$($簡稱SHG$)$量測
，研究摻雜對長晶、摻雜之離析及光學性質之影響。 $VDGF$法中摻雜之
軸向離析主要受擴散控制；而徑向離析則主要受界面之對流環型態與界面
形狀影響，且軸向離析亦導致徑向離析隨軸向位置而異。 摻雜安息香可
減少劈裂之產生，此應是由於安息香可提供氫鍵，增加力學強度。因$
Nd^{3+}$不易嵌於苯偶醯晶格中，摻雜高濃度$Nd^{3+}$會產生多量破碎
狀細裂紋；摻雜低濃度$Nd^{3+}$可減少面滑移之劈裂。可能是因$Nd^{3+
}$造成之因局部破碎狀細裂紋可提供熱應力之釋放所致。 摻雜$Nd^{3+
}$可提高苯偶醯之$SHG$轉化率，且$Nd^{3+}$濃度愈高則$SHG$轉化率愈
高。$Nd^{3+}$亦能導致苯偶醯光破壞強度降低，及光破壞後劈裂面擴大
速度減慢。適當地將有機晶體吸收光能量產生之熱量傳導出，可減少熱應
力，而有增加光破壞強度之趨勢。

Due to the highly nonlinear optical properties and the
versatility in synthesis, organic materials are quite promising
in optics devices. Crystal properties, mainly determined by the
growth environment and impurities segregation, are very
important in application. The vertical dynamic gradient freeze
(VDGF) technique using a transparent furnance was applied to the
growth of benzil single crystal for nonlinear optics. The
effects of dopants on crystal growth, segregation and optical
properties were studied by growing observation and sequential
measurements of dopants concentration and second harmonic
generation (SHG). In the VDGF method, axial segregaton of
dopant is mainly controlled by diffusion and radial segregation
is mainly affected by the flow pattern near interface and
interface shape. Due to axial segregation, radial segregation
varies along the axial position. Doping benzoin to benzil can
reduce cracks. It is possible due to benzoin offering hydrogen
bonding and increasing mechanical strength of benzil. Because it
is not easy for $Nd^{3+}$ to be embeded in benzil crystal
lattice,doping high concentration of $Nd^{3+}$ will cause many
small shattered-like cracks. However the cracks caused by planes
glide were reduced at low $Nd^{3+}$ concentration, such as 1.24
ppm. $Nd^{3+}$-doped benzil has a higher SHG conversion
efficiency than the pure benzil. As the $Nd^{3+}$ concentration
increased, the conversion efficiency increased.The small cracks
tendency may also reduce radiation damage threshold.By releasing
the heat trapped in the crystal, the radiation damage threshold
may increase.