We analyze experimentally and theoretically the chaotic dynamics generated by a laser diode subjected to phase-conjugate feedback. Phase-conjugation is obtained from four-wave mixing in a BaT i0 3 photorefractive crystal. We demonstrate that the chaos bandwidth first increases linearly with the feedback ratio but then saturates to relatively high values. A chaos bandwidth up to about 18 GHz is achieved, which is more than five times larger than the free-running laser diode relaxation oscillation frequency. Numerical simulations confirm our experimental observations and unveil that the finite depth penetration into the crystal is responsible for the observed saturation.