KDP晶体拉曼散射角度特性

利用群理论详细分析了磷酸二氢钾(KDP)晶体的拉曼振动模式,得出了其拉曼振动模的归类。并采用拉曼光谱仪测量了Z切退火KDP晶体X(ZZ)珡X,Z(XY)珚Z和Y(XY)X三种散射配置和未退火KDP晶体Z(XY)珚Z配置下的拉曼光谱。根据拉曼选择定则得出X(ZZ)珡X,Z(XY)珚Z和Y(XY)X散射配置下的拉曼峰分别对应A1,B2(LO),B2(TO)对称类振动模,但在Z(XY)珚Z配置下的拉曼光谱中除了B2模,还观察到了A1模,而在Y(XY)X配置下的拉曼光谱中只有B2模,且退火和未退火晶体Z(XY)珚Z配置下的拉曼光谱无明显差别,此结果表明KDP晶体的对称性降低,在背向散射时A1模也具有角度特性,但与晶体的内应力无关,这是由KDP晶体内部结构决定的。

Analysis on the Raman scattering angular dependence of KDP crystal

The Raman vibration modes of potassium dihydrogen phosphate (KDP) crystal were analyzed by the group theory in detail, and the Raman vibration modes were well assigned. The Raman spectra of type Z annealed KDP crystal in X(ZZ)X, Z(XY)X and Y(XY)X scattering geometries and type Z unannealed KDP crystal in Z(XY)Z scattering geometry were also measured by Raman spectrophotometer system. According to the selection rules we found that the Raman peaks in X(ZZ)X, Z(XY)X and Y(XY)X scattering geometries correspond to A1, B2(LO) and B2(TO) modes respectively. However, in the Z(XY)Z scattering geometry, A1 modes appear besides B2 modes, and in Y(XY)X scattering geometry there exist B2 modes only. What is more, the Raman spectra of annealed and unannealed KDP crystal in Z(XY)Z scattering geometry show no obvious difference. The results indicate that the symmetry of KDP crystal is lower and A1 modes possess angular dependence in Raman back-scattering geometry, which is determined by crystal structure and independent of lattice internal stress.