Mutually pumped phase conjugators with picosecond pulses

Mutually pumped phase conjugators with picosecond pulse trains are experimentally demonstrated in rhodium-doped barium titanate. Stable phase-conjugate reflectivities are obtained when the counterpropagating pulses do not meet in the crystal. In contrast, when the pulses do meet in the crystal the reflectivities become unstable and unequal in value in two directions. This behavior is caused by the interference between two counterpropagating pulses. In addition, the reflectivities for the picosecond pulses are found to be half of those for continuous waves. The reasons for the small reflectivities of the pulses are discussed. (C) 1998 Optical Society of America.