Construction of Precise Analysis System of Conoscopic Images in Liquid Crystals

1. 我们构建了一种利用He-Cd激光观测conconscopic图像的系统，该系统是波长最短的光源之一。我们构建了一个用4x4矩阵法分析conconscopic images的程序。我们利用所构建的系统详细观察了铁电液晶在电场作用下的螺旋解绕过程，得到了以下结果：实验结果与基于弹性理论的场致螺旋解绕过程的4x4矩阵方法的仿真结果一致。特别是，负双轴性是通过施加电场观察到的，并从理论上加以解释。到目前为止，负双轴性被认为是铁电相的特征，并被用来识别铁电相。然而，我们澄清了场致负双轴性通常在铁电相中观察到，不能用于识别铁电相。我们发现，先前在MHPOBC中首次证实反铁电相的conconscopic观察是在不充分的场强下进行的，不能诱导完全的螺旋解绕。我们利用足以诱导螺旋完全解绕的高场，重新详细观察了conconscopic图像。结果表明，仅考虑电场与极化之间的铁电相互作用不能解释MHPOBC中螺旋解绕过程。

1. We constructed a system to observe conoscopic images using a He-Cd laser, which surves one of shortest wavelength light sources.2. We constructed a program for analyzing conoscopic images using the 4x4 matrix method.3. We observed helix unwinding processes in ferroelectric liquid crystals by an electric field in detail utilizing the constructed system, and obtained the following results.3-1. The experimental results agree with the simulation results by the 4x4 matrix method based on the field-induced helix unwinding process by elastic theory. Particularly, negative biaxiality was observed by the application of an electric field and was theoretically explained.3-2. So far, the negative biaxiality was thought to be characteristic in ferrielectric phases and was used to identify the ferrielectrie phase. However, we clarify that the field-induced negative biaxiality is generally observed in the ferroelectric phase and cannot be used to identify the ferrielectrie phases.3-3. We found that the previous conoscopic observation in MHPOBC, in which the antiferroelectric phase was first confirmed, was made using unsaficient field strength, that cannot induce complete helix unwinding. We reobserved the conoscopic images in detail by applying high fields saficient to induce complete helix unwinding. As results, we concluded that the helix unwinding process in MHPOBC cannot be explained only by considering ferroelectric interaction between the applying field and the polarization.