Picosecond pulse amplification by coherent wave mixing in silicon

Pulses from Nd:YAG lasers (where YAG represents yttrium aluminum garnet) were amplified up to 20 times by noncollinear mixing with a coherent pump wave in silicon. Amplification of long pulses (about 16 ns) was obtained with intersection angles up to 2^∘{} whereas angles larger than 10^∘{} are possible with short pulses (50 ps). The effect is theoretically described by self-diffraction at a laser-induced dynamic free-carrier grating.