Femtosecond Z-scan measurement of third-order nonlinear refractive indices of BaMgF4

The BaMgF4 single crystal is grown by Bridgman method. The third-order nonlinear refractive indices along three crystallographic axes are determined by Z-scan technique with femtosecond laser. The largest one that has a value of 2.35×10−18 m2/W is along the c-axis and the corresponding third-order nonlinear susceptibility is 1.24×10−12 esu. This value is compared with LiNbO3 through self-phase modulation effect. Furthermore, the mechanism and the possible applications of the relatively large third-order nonlinear refractive indices are also discussed at last.