Hryhorashchuk A. Optical oscillation in photorefractive crystals with bipolar conductivity

The thesis is devoted to the study of the dynamic characteristics of new oscillation mode in semilinear optical coherent oscillator, built on photorefractive crystal with bipolar conductivity. Crystals used are ferroelectric tin hypothiodiphosphate (Sn2P2S6). Dynamics of output beam intensity is nearly saw-tooth modulated with phase of the output beam switching by ? with each consecutive pulse while remaining unchanged during each separate pulse. The model is proposed to describe the origin of such oscillation. It is based on interaction of space charge field gratings formed by holes and electrons and is shown that the gratings can be not only anti-phase but also in-phase. It is shown that oscillation processes in semilinear optical oscillator, based on crystal with bipolar conductivity, are similar to those in symmetrical electrical multivibrator. The study of semilinear oscillator based on crystal with bi-polar conductivity for ultimate coupling strength (?l>7) is performed, when frequency non-degenerate oscillation occurs.