ESTABLISHMENT OF COHERENT PHONON EXCITATION --as a new method for phase transition study--

一个新的实验方法，Coherent Phonon Exitation，它是一个很好的术语，用于1998年至2000年两年内的当前研究项目的研究阶段。这一方法提供了对软兴奋的直接观察，与相位转换动力学密切相关。软声子运动的时间依赖性和/或相对运动的时间依赖性是精确的，因为它们的时间依赖性是因为它们运动的等式通常是由时域驱动的。作为目前项目的结果，实验系统的特别改进已经完成了使用光学干扰板（相位掩码）和对来自兴奋的声子的光线差异的异丁二烯检测。这个项目已经被简化为后续活动; 1. Soft ferroelectric B-D22-D2 mode of KDP has been excited and observed its time dependence as a function of temperature in a range from RT to Tc. A clear single exponential time dependence of the BイイD22イエD2 mode even 30 K far above Tc indicates an order-disorder type phase transition dynamics in KDP。2. A precise observation of the dispersion relation of the phonon-polariton of the ferroelectric LiNbOイD23イエD2 has been done at room temperature。由于目前的方法在一个小波矢量区域中具有优势，因此，A-D21-D2声子-polariton的差异关系被确定为高准确性，在对比到几个共振点以下7 THz以下的研究中报告了一个非常简单的曲线。3.玻璃液体过渡中的一种超缓慢的放松运动已经被精确地研究过，由波矢量定义。

A new experimental method COHERENT PHONON EXCITATION, which is quite adequate for the study of phase transition has been established during the period of the present research project for two years from 1998 to 2000. This method provides a direct observation of the soft excitations closely related to the phase transition dynamics. The time dependence of the motion of the soft phonon mode and/or a relaxational mode are precisely distinguishable by their time dependence because the equation of motion of thoes excitation is usually driven in the time domain. As a result of the present project, a special improvement of the experimental system has been completed using an optical interference plate (phase mask) and heterodyne detection for the light diffracted from the excited phonons. The project is summarized as follows; 1. The soft ferroelectric BィイD22ィエD2 mode of KDP has been excited and observed its time dependence as a function of temperature in a range from RT to Tc. A clear single exponential time dependence of the BィイD22ィエD2 mode even 30 K far above Tc indicates an order-disorder type phase transition dynamics in KDP. 2. A precise observation of the dispersion relation of the phonon-polariton of the ferroelectric LiNbOィイD23ィエD2 has been done at room temperature. Because the present method has advantage in a small wave vector region, the dispersion relation of the AィイD21ィエD2 phonon-polariton is determined with high accuracy elucidating a very simple curve in contrast to the several resonance points below 7THz reported in the previous studies. 3. An ultra-slow relaxational motion in the glass-liquid transition has been studied with wave vectors defined precisely.