Unusually fast mutually pumped phase-conjugation (MPPC) is achieved in
a Bi12TiO20 crystal by using transient photorefractive beam coupling
under a de electric field. Pulses of phase-conjugate waves with a buil
dup time of 4.5 ms and a width of 50 ms at an input intensity of 2 x 0
.8 W/cm(2) are obtained after applying a rising front of external elec
tric field to the crystal. A phase-conjugation efficiency as high as 2
5% of the incident light power is measured. (C) 1997 American Institut
e of Physics.