Instabilities in Coupled Photorefractive Ring Cavities and Self-Pumped Phase Conjugators,
NATIONAL CHIAO TUNG UNIV HSINCHU (TAIWAN)
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Photorefractive mode coupling between resonators provides a simple model for self-pumped phase conjugators where instabilities may occur due to energy transfer between different oscillation modes inside the crystal. In this paper, we consider the dynamical behaviors of mode coupling between two unidirectional ring resonators. The first resonator is driven by an external laser beam via photorefractive two-wave mixing. The internal oscillating beam is then employed to drive the second ring resonator via the same mechanism. The dynamics of the coupled system is described by a set of spatial-temporal equations with appropriate boundary conditions. To investigate the instability behaviors, we use the mean-field approximation to simplify the transient analysis. We first solve for the steady states of the system. When the gain of the two cavities are below certain threshold, there is no self-oscillation in the system. If the gain for the primary cavity is increased above its threshold while the gain for the secondary cavity remains low, self-oscillation will occur in the primary cavity only. If the gain in the secondary cavity is gradually increased, self-oscillation will occur in the secondary cavity.
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