Periodical poling of MgO doped lithium niobate crystal fiber by modulated pyroelectric field

In situ poling of MgO doped lithium niobate crystal fiber during laser heated pedestal growth is presented. The poling mechanism is mainly attributed to the micro-swing-induced modulation of the pyroelectric field in the fiber. Strong charge screening effect, which blocks the applied electric field, is observed within 1.2 mm from the molten zone. The required poling field, ∼1 kV/mm, is therefore much higher than the coersive field near the Curie temperature and yet much lower than that of on planar lithium niobate devices. The dependence of poled pattern on growth condition and electric-field bias are studied. The whole cross-section as seen from the y- and z-faces of lithium niobate crystal fiber is poled through, and a domain period of 9.76 μm is obtained with a diameter variation of less than 0.7%.