Amplified reflection, phase conjugation, and oscillation in degenerate four-wave mixing.

The purpose of this Letter is to examine briefly the consequences of a certain class of four-wave mixing. This mixing involves two intense pun-p waves E1 and EB of the same frequency w traveling in opposite directions and two "weak" waves E 3 and E4 of the same frequency w, which aiso travel in opposition to each other but along a direction different from that of E1 and E2 . The geometry is illustrated in Fig. 1. The fields are taken as plane waves