Hyper-resolution Brillouin-rayleigh Spectroscopy by Optical Beating Technique

自60年代中期Fleury和Chiao首次成功地观测到布里渊三重态以来，由扫描法布里-珀罗干涉仪和高灵敏度光电倍增管组成的光散射系统一直是所有布里渊散射实验的通用标准。已尽一切奋进来提高实验的分辨率，但一般认为这并不令人满意。例如，已经开发了一种非常复杂的系统，其中计算机控制多程法布里-珀罗标准具或串联的标准具。为了减少由光源的光谱宽度引入的额外的谱线展宽，已经利用了具有频率稳定装置的单纵模激光器，由此产生的输出功率的缺乏通过随后是光子计数器的冷却光电倍增管的增加的检测灵敏度来补偿。因此，今天的布里渊散射系统变得越来越复杂， ...更多信息 但其实质部分仍停留在弗勒里和焦的实验中。然而，所有这些努力，以实现更高的分辨率似乎已经得到回报，而有限的成功。另一方面，一个想法的布里渊散射实验的基础上，一个完全不同的原则，即，用光谱分析仪代替法布里-珀罗标准具的光拍频光谱技术。沿着这条路线已经进行了沿着各种各样的实验，但大多数都不成功，只有一个例外。最近，我们成功地开发了一种新的超分辨率布里渊散射系统，其频率分辨率提高了10^3-10^4倍。在本研究中，我们进一步改进了光散射系统，并利用该系统进行了一些复杂的实验，包括（1）观察聚合物固体中的声子弛豫现象，（2）发现热声子共振和（3）研究非平衡态下观察到的布里渊三重态的不对称性。少

The light scattering system with a scanning Fabry-Perot interferometer and a high-sensitivity photo-multiplier has long been the general standard of all the Brillouin scattering experiments ever since Fleury and Chiao first succeeded in the observation of a Brillouin triplet in the middle of the 1960's. Every endeavor has been made to improve the resolution of the experiment, which has not generally been considered satisfactory. A very sophisticated system in which a computer controls multipass Fabry-Perot etalon or etalons in tandem, for example, has been developed. To reduce the additional line broadening introduced by the spectrum width of the light source, a single longitudinal mode laser with a frequency-stabilizing device has been utilized, the resultant lack of output power being compensated by the increased detection sensitivity of a cooled photo-multiplier tube followed by a photon counter. The Brillouin scattering system of today is thus becoming more and more complicated tho … More ugh its essential part still stays within the experiment of Fleury and Chiao. Nevertheless, all these efforts to achieve higher resolution seems to have been rewarded with rather limited success.On the other hand, the idea of a Brillouin scattering experiment base on a completely different principle has been proposed, i.e., the technique of light beating spectroscopy in which the Fabry-Perot etalon is replaced with a spectrum analyzer. Various experiments have been tried along this line, but most of them were unsuccessful with only one exception. Recently we succeeded in the development of a new system of hyper-resolution Brillouin scattering in which the frequency resolution was increased by 10^3-10^4 times. In this study, we further improved the light scattering system with which we conducted some sophisticated experiments, including (1) observation of phonon relaxation phenomenon in polymer solids, (2) discovery of thermal phonon resonance and (3) investigation of asymmetry in Brillouin triplet observed under non-equilibrium state. Less