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Mixed (FAPbI3)0.92(MAPbBr3)0.08 perovskite thin films exhibit strong nonlinear optical responses, rendering them promising candidates for applications in photonics and optical communications. In this work, we present a systematic study on the ultrafast third-order nonlinear optical processes in mixed perovskite nanocrystals (NCs) by exploring the generation of third harmonic radiation and giant two-photon absorption-based photoluminescence (PL) when excited by femtosecond laser pulses of a 1030 nm central wavelength. A comparative analysis of the coherent third harmonic generation in the thin-film-containing perovskite nanocrystals has shown a 40× enhancement of the third harmonic signal compared to the signal generated in the pure quartz substrate. The cubic dependence of the third-nonlinear optical response of the (FAPbI3)0.92(MAPbBr3)0.08 perovskites on the intensity of the driving radiation was identified using broadband 38 femtosecond driving pulses. The positive nonlinear refractive index (γ = +1.4 × 10−12 cm2·W−1) is found to play an important role in improving the phase-matching conditions of the interacting pulses by generating a strong third order harmonic. The giant two-photon absorption (TPA)-assisted PL peak was monitored and a blue shift of the PL was obtained in the higher intensity range of the laser pulses, with the absorption coefficient β estimated to be~+7.0 cm·MW−1 at a 1030 nm laser wavelength.

Ultrafast laser ablation of metal surfaces is a common physical process used to generate periodic surface structures with tuneable multifunctionality for various applications in science and technology. In this work, the formation of femtosecond laser-induced periodic surface structures (LIPSS) is investigated with 50 kHz repetition rate laser of 40 fs pulse duration and a central wavelength (λw=1030nm) along with its second (λ2w=515nm) and third (λ3w=343nm) harmonic components. The variation in the LIPSS periodicity is demonstrated by changing the wavelength of the ablating laser pulses. LIPSS with periodicity ~ 0.85 μm at the fundamental ablating pulses, ~0.42 μm periodicity at the second harmonic, and ~0.35 μm periodicity at the third harmonic generation were observed. We apply the third harmonic radiation generated in air filament with minimal temporal delay with respect to the fundamental driving pulses to structure nickel surfaces at ambient conditions. Our presented approach demonstrates the potential for generating very fine LIPSS on materials’ surfaces using the efficient high-order harmonics of an infrared fundamental laser beam.

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We synthesize Zn and ZnSe nanoparticles during laser ablation of bulk material in ethanol and analyze them using the Z-scan technique and the generation of high harmonics using a 50 kHz, 40 fs, and 1030 nm laser. The low-order nonlinear absorption and nonlinear refraction coefficients in the colloidal suspensions of the formed nanoparticles were measured using 1030 nm and 515 nm probing laser pulses, respectively. The values of the nonlinear refractive index and nonlinear absorption coefficient of Zn NPs at 1030 nm wavelength were calculated to be γ = − 1.4 × 10 − 13 c m 2 W − 1 and β = 2.7 × 10 − 11 c m W − 1 , respectively. Similarly, in the case of ZnSe NPs, γ = − 4.9 × 10 − 14 c m 2 W − 1 and β = 0.5 × 10 − 11 c m W − 1 , respectively. In the case of 515 nm probing pulses, the corresponding nonlinear optical parameters of Zn NP suspension were calculated to be γ = − 1.7 × 10 − 14 c m 2 W − 1 and β = 1.0 × 10 − 11 c m W − 1 , and for ZnSe NP suspension, the value of β was calculated to be 2.1 × 10 − 11 c m W − 1 . The nonlinear refractive index of this suspension was γ = − 2.4 × 10 − 14 c m 2 W − 1 . We also report the studies of high-order harmonics generation in plasmas containing Zn and ZnSe NPs using single- (1030 nm) and two-color (1030 nm + 515 nm) laser fields. The maximal generated extreme ultraviolet (XUV) harmonics were 33rd (Zn NPs) and 27th (ZnSe NPs) orders. The decrease of the maximal generating harmonic orders was explained using the three-step model. The high brightness of the ninth and 10th harmonics generated in the two-color laser field was obtained due to the resonance properties of Zn NPs. The maximal generated XUV harmonics were the 33rd (Zn nanoparticles) and 27th (ZnSe nanoparticles) orders.