Nanometer Polarization Control Devices and Coherent Detection

本文用电子束辐照和外加电场的方法研究了LiTaO_3（LT）和LiNbO_3（LN）晶体中纳米级反转畴的形成，得到了以下结果：1）测量了电子束辐照晶体时电子撞击晶体所产生的库仑力。本文导出了在画出一个小点之前，用不同的电子密度画出一个小点与周围环（控制环）之间的库仑相互作用方程。然后绘制了相同密度不同尺寸的控制环，并与原设计的控制环尺寸进行了比较。与预期的图案尺寸一致。研究表明，LN和LT畴反转的机理分别对应于两种方法，并通过控制合适的表面可磁化率，利用光学级LN成功地获得了几百nm的反转畴尺寸。2）提出了纳米级畴反转成像的相干探测方法。该系统由原子力显微镜单元和压电锁定放大器组成。3）采用畴反转的“全覆盖电极法”制作了高效率的倍频蓝光源。4）提出了一种新型的LN行波光调制器结构（背槽型），并对其进行了优化设计。调制速率达到40Gbps，驱动电压达到2.8V。

We Have been studying the formation of nanometer scale inversion domains in LiTaO_3 (LT) and LiNbO_3 (LN) using an electron beam (EB) irradiation and an external electric field applied method.In this study, we have been obtained the following results ;1) The Coulomb force caused by the electrons impinging into crystal by EB irradiation were measured. We led the equation for the interaction of Coulomb between a small dot and a surrounding ring (control-ring) which is drawn with various electronic densities before drawing of a small dot. Then we drawn the control-ring with same density and different size and compared the size of inverted pattern with the original designed one. There was good agreement with the pattern size as expected. It has been clear that the mechanism of LN and LT domain inversion corresponding to two method, and a few hundred nm inverted domain size has been successfully obtained by using the optical grade LN which where controlled suitable surface resistibility.2) The coherent detection for imaging domain inversion of nanometer scale has been proposed. This system is composed of AFM unit and Piezo-active and Lock-in amp. units.3) A high efficiency SHG blue light source was fabricated by using a new method called "Full Cover Electrode Method" of domain inversion.4) A new structure (Back slot type) and the optimum design for LN traveling wave optical modulator are proposed. Modulation speed 40 Gbps, and driving voltage 2.8V was achieved.