【摘要】 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。更多还原

【Abstract】 Optical properties of the novel single Ca_0.28Ba_0.72Nb₂O₆ （CBN-28） crystal at room temperature are investigated in this paper. The transmission and refractive index of Ca_0.28Ba_0.72Nb₂O₆ as a function of wavelength are measured by the double beam spectrophotometer and the spectroscopic ellipsometry respectively. The normal dispersions were observed, and the ordinary refractive index n_o is larger than the extraordinary index n_e, which implied that this crystal is a negative uniaxial crystal. The dispersion curves show that the birefringence is up to about 0.12 in the short wavelength range. The transmission spectrum demonstrates that this crystal is transparent from 400 nm to 900 nm. And the absorption coefficient and its square root were calculated according to the transmittance. The direct and indirect energy gap and phonon energy for this crystal have been estimated respectively. As a result, the band gap is 3.33 eV, and the indirect band gap energy is 2.94 eV with the phonon energy 0.17 eV. By changing the vibration directions of the polarizer in the optical system, the transmission spectra of the ordinary light and extraordinary light are obtained. The absorption coefficients of these two lights are calculated.更多还原