Z-scan measurement of the nonlinear refractive index of Nd(3+), Y(3+)-codoped CaF(2) and SrF(2) crystals.

By performing the Z-scan measurements at 800 nm using a femtosecond pulsed laser, we are able to characterize the nonlinear refractive indices of Nd, Y codoped CaF(2) and SrF(2) crystals. Based on our measured results, we conclude that the doped fluoride crystal possesses a small nonlinear refractive index and the doping of Nd(3+) and Y(3+) ions in CaF(2) can change its third-order nonlinear index, but the contribution is minor. The doped fluoride crystal may have large potential to be developed as the next generation of gain material for a high-energy laser system.