Low- and high-order nonlinear optical properties of Au, Pt, Pd, and Ru nanoparticles

We investigate third- and higher-order nonlinear optical processes in Au, Pt, Pd, and Ru nanoparticles. We measured the nonlinear refractive indices and nonlinear absorption coefficients of the suspensions of these nanoparticles using the 792 nm femtosecond and picosecond pulses. The highest values of these parameters were observed in the case of Au nanoparticles (-8x10-14 m2 W-1 and 1.7x10-10 m W-1), when the 210 ps pulses were used as a probe radiation. The high-order harmonic generation was studied during the propagation of the 120 fs pulses through the plasmas produced on the surfaces containing the nanoparticles. The highest harmonic cutoff (33rd order) was observed in the case of gold nanoparticle-contained plasma. These results were compared with the harmonics generating from the plasma produced on the surfaces of the bulk materials of the same origin. A two- to sixfold enhancement of harmonic yield was observed in the case of nanoparticle-contained plumes with regard to the bulk materials