采用超快半导体光电导开关的宽带太赫兹时域频谱系统，研究了 KTiOPO4 晶体在0.5～2.0THz波段的光学声子振荡特性；在晶体z轴平行于THz波电场振动方向时发现了明显的吸收峰.利用晶体中晶格振动模式（光学声子）对光谱的选择性吸收特性和多洛仑兹振子伪谐振介电模型，很好地拟合了KTP晶体的复介电常量曲线，得到了对应晶格弱振动的光学声子的频谱参量值.研究结果表明，位于ω1 /2π=1.76 THz的吸收峰是KTP晶体中沿z轴排列的K+相对于PO4和TiO6晶格振动造成的光学外振动模.同时也说明THz波对于晶格弱振动非常敏感，对于微弱的光学声子吸收峰的频谱分析更加精准.

Utilizing ultrafast femtosecond pulses to pump photoconductive switches in the terahertz time-domain spectroscopy system,the optical phonon oscillation characteristics of KTiOPO4 crystal were studied in the 0.5~2.0THz range.An obvious absorption peak was found when the z-axis of the crystal was parallel to the polarization of the terahertz electric field.With the crystal lattice vibration selective absorption principle and pseudo-harmonic dielectric model,the complex dielectric constant curves fit well and the spectroscopic parameters of a weak optical phonon resonance were achieved.The optical external mode at ω1/2π=1.76THz,which attributed to the K ions vibration relative to the screw of PO4 tetrahedral and TiO6 octahedral,was confirmed.These results show that the THz time-domain spectroscopy is more sensitive and precise to weak lattice vibrations.