Z-scan measurements of nonlinear refractive indices of NaT(XO4)2 T= Y, La, Gd, Lu and Bi, X= Mo, W, femtosecond laser crystals

• The characterization of the coefficient of the nonlinear optical Kerr effect, the nonlinear refractive index (n(2)), of several femtosecond laser crystals with compositions derived by total or partial replacement of D(2+) in DXO(4), X = Mo or W, is presented. Tetragonal (space group I4) Na-based double tungstates NaT(WO(4))(2) (T = Y, La, Gd, Lu and Bi) and double molybdate NaY(MoO(4))(2), as well as the monoclinic (space group C2/c) Li(3)Gd(3)Ba(2)(MoO(4))(8) crystals, have been measured by the z-scan technique. All these crystals present structural local disorder, and among them the tetragonal ones exhibit significant n(2) values, which should allow their efficient laser pulsed operation by Kerr-lens mode locking, especially NaBi(WO(4))(2), 68x10(-16) cm(2)/W (for sigma light), which is about twice than for the others. This feature is attributed to the high polarizability associated to the lone electron pair of Bi(3+).

Nyckelord

nonlinear refractive index; z-scan technique; ultrashort laser pulse; disordered laser crystal; double tungstate laser crystal; double molybdate laser crystal; ternary molybdate laser crystal

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