Three-beam amplification in BSO crystals

It is shown that by applying the right detuning to two pump beams incident upon the BSO crystal from the same side, a third signal beam may be amplified. The maximum amplification was 12000 for a 1 cm-thick crystal which represents the highest value ever measured in BSO. It is further shown that the amplification strongly depends on the input power of the signal beam and full amplification is achieved for a beam ratio in excess of 10⁷.