Measurement of space-charge field in doped LiNbO3 single crystals

In order to measure the space-charge field in MgO-doped LiNbO₃, we examined the variation of second-harmonic intensity by an external DC electric field and a single beam pump. Intensities of illuminated beam were 3.9 and 7.8 W/cm². An external DC field was applied in the direction of spontaneous polarization (i.e. c-axis). Generated second-harmonic intensity as a function of DC electric field represented by the function of (cosine)². Space-charge field formed as a function of the exposure time of a laser beam had a exponential function. In 4 mol% MgO-doped LiNbO₃ of 6.8 kV/cm at 3.9 W/cm², the saturated space-charge field had a minimum value and the relaxation time had a maximum value.