Abstract: The nonlinear optical coefficients of the borophosphate crystal BaBPO5 were measured by the maker fringe fringe technique:d11(BaBPO5)=(0.439±0.002)d36(KH2PO4),d13(BaBPO5)=(0.425±0.008)d36(KH2PO4), at the 1064nm fundamental light. The experimental results were agreement with the theoretical ones well . And the coherent lengths of BaBPO5 were calculated : l11=16.985±0.301μm,l12=16.972±0.304μm. The relative sign of the coefficients and the coherent lengths of BaBPO5 crystal were determined. And the optical damage threshold was estimated for the laser beam (10ns pulse, 1064nm and 10Hz), which is more than 900 MW/cm2.

Key words: The nonlinear optical coefficients of the borophosphate crystal BaBPO5 were measured by the maker fringe fringe technique:d11(BaBPO5)=(0.439±0.002)d36(KH2PO4),d13(BaBPO5)=(0.425±0.008)d36(KH2PO4), at the 1064nm fundamental light. The experimental results were agreement with the theoretical ones well . And the coherent lengths of BaBPO5 were calculated : l11=16.985±0.301μm,l12=16.972±0.304μm. The relative sign of the coefficients and the coherent lengths of BaBPO5 crystal were determined. And the optical damage threshold was estimated for the laser beam (10ns pulse, 1064nm and 10Hz), which is more than 900 MW/cm2.