Nanometer Polarization Control Devices and Coherent Detection

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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.