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研究了室温下铌酸钙钡单晶的光学性质。分别用分光光度计和椭偏光谱仪测量了铌酸钙钡晶体的透射率和折射率随波长的变化关系,结果表明铌酸钙钡晶体具有正常色散关系,且寻常光折射率no 大于异常光折射率ne,说明该晶体为负的单轴晶。折射率之差在短波区达到0.12。透射率光谱显示该晶体在 400~900 nm波段是透明的。根据透射率计算了该波段晶体的吸收系数以及它的平方根。通过对该曲线的研究,发现铌酸钙钡晶体吸收边以下对应的跃迁为间接跃迁,计算出间接跃迁的禁带宽度Eg 为2.94 eV以及声子能量 Ep 为 0.17 eV。此外,通过改变系统光路中偏振片的透振方向,获得了寻常光和异常光的透射率,并进一步计算了它们的吸收系数。
The optical properties of barium calcium niobate single crystals at room temperature were studied. The relationship between the transmittance and the refractive index of the barium niobate crystal with wavelength was measured by spectrophotometer and ellipsometer respectively. The results show that the barium niobate crystal has the normal dispersion relation and the ordinary refractive index no is larger than that of the extraordinary light Rate ne, indicating that the crystal is negative uniaxial crystal. The difference in refractive index reaches 0.12 in the short wavelength region. The transmittance spectrum shows that the crystal is transparent in the 400-900 nm band. The absorption coefficient of the crystal in this band and its square root are calculated based on the transmissivity. Through the study of this curve, it was found that the corresponding transition below the absorption edge of barium calcium niobate crystal was an indirect transition, and the bandgap Eg of indirect transition was 2.94 eV and the phonon energy Ep was 0.17 eV. In addition, by changing the transmission direction of the polarizer in the optical path of the system, the transmittance of ordinary light and abnormal light are obtained, and their absorption coefficients are further calculated.