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The optical limiting properties of alloyed CdZnS quantum dots associated with erythrosine dye are analyzed using 532 nm, 40 ps pulses. We show that joint influence of saturable absorption, reverse saturable absorption and two-photon absorption cause the optical limiting of 532 nm radiation at the pulse energies exceeding 1 mJ. The nonlinear refraction and nonlinear absorption of these quantum dots associated with different organic dyes were studied using 1064 nm and 532 nm radiation. The nonlinear refraction index and nonlinear absorption coefficient of CdZnS quantum dots were measured at λ = 1064 nm to be 2 × 10 cm W and 1.2 × 10 cm W, while the reverse saturable absorption of CdZnS quantum dots and erythrosine at λ = 532 nm was almost two orders larger. The potential applications of these quantum dots for high-order harmonic generation are discussed.

As high-order harmonic emitters, quantum dots are produced through laser-induced plasmas. Subsequently, we generate high-order harmonics with 800-nm and 30-fs pulses from laser-produced plasmas containing quantum dots of different metal sulfides (Ag2S, CdS, and Cd0.5Zn0.5S). The high-order harmonic generation is analyzed using different approaches, including two-color (800 nm + 400 nm) pump, application of alloyed quantum dots, and quasiphase matching of interacting waves. We discuss the self-phase modulation induced splitting of harmonics, the difference in the application of thick and thin crystals for second harmonic (400 nm) emission during two-color pumping of the quantum dot plasma, the spatial modulation of the quantum dot plasma for quasiphase matching, and the comparison of harmonic yields from monomer and quantum dot plasmas. This study allows us to determine the mechanisms of coherent extreme ultraviolet radiation generation using a few nanometer-sized emitters as well as optimal methods for further enhancing the high-order harmonic generation efficiency.