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DEVEROPEMENT OF NONLINEAR RELAXATION SPECTROMETER IN A FREQUENCY DOMAIN

频域非线性弛豫谱仪的研制

基本信息

批准号：
09555020
负责人：
HAYAKAWA Reinosuke
金额：
$ 7.3万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

项目摘要

As a response to external field easily becomes nonlinear in soft condensed matters such as polymers and liquid crystals, the nonlinear relaxation spectroscopy is an useful method to investigate the dynamics of these matters. We have developed the nonlinear relaxation spectrometer in a frequency domain using a sinusoidal electric field as an input. In our system, harmonic distortion of the applied electric field has been removed by low-pass filter and the nonlinear responses have been extracted from response signals after cancel of the fundamental component by the digital balancing method. The digital balancing method makes it possible to measure the nonlinear spectra with high accuracy free from the dynamic range of the spectrometer.We have applied the developed system to ferroelectric liquid crystals in the SmC^* phase and checked the usefulness of the system. The measured linear and third-order nonlinear spectra are found to make good agreement with those calculated theoretically. We have succeeded in the evaluation of the material constants which are important in the display application such as spontaneous polarization and rotational viscosity by the comparison between those two spectra.We have also applied that system to the nonlinear electrooptic measurement, in which the intensity of the transmitted intensity through cells filled with ferroelectric liquid crystals is detected as an output signal. It is found the odd harmonic spectra offer the similar information to that obtained from the nonlinear dielectric spectra and the even harmonic spectra offer the information on the electric and optical anisotropy of liquid crystals.In conclusion, we have developed new nonlinear relaxation spectrometer and showed the usefulness of the system in the study of dynamics of liquid crystals.

由于聚合物和液晶等软凝聚态物质对外场的响应很容易变得非线性，因此非线性弛豫光谱是研究这些物质动力学的有用方法。我们开发了频域非线性弛豫光谱仪，使用正弦电场作为输入。在我们的系统中，低通滤波器消除了所施加电场的谐波失真，并通过数字平衡方法消除基波分量后从响应信号中提取非线性响应。数字平衡方法使得不受光谱仪动态范围影响的高精度非线性光谱测量成为可能。我们已将开发的系统应用于SmC^*相铁电液晶，并检验了该系统的实用性。发现测量的线性和三阶非线性光谱与理论计算结果非常吻合。通过比较这两个光谱，我们成功地评估了在显示应用中很重要的材料常数，例如自发极化和旋转粘度。我们还将该系统应用于非线性电光测量，其中通过填充铁电液晶的单元的透射强度被检测为输出信号。研究发现，奇次谐波谱提供了与非线性介电谱相似的信息，偶次谐波谱提供了液晶电各向异性和光学各向异性的信息。总之，我们开发了新型非线性弛豫谱仪，并展示了该系统在液晶动力学研究中的有用性。