Нелинейно-оптические свойства квантовых точек CdS/ZnS в матрице из высокомолекулярного поливинилпирролидона

AbstractSols containing core/shell CdS/ZnS semiconductor quantum dots are synthesized and their nonlinear properties, which are interesting for a large variety of applications in nanophotonics, are studied. The quantum dots produced are smaller in dimensions than the exciton Bohr radius and, therefore, exhibit a well-pronounced quantum-confinement effect. The nonlinear optical properties of low-concentration sols are studied upon exposure to laser pulses with an emission wavelength of 532 nm and a duration of 5 ns by the z-scan technique. The dependences of nonlinear optical coefficients on the concentration of CdS/ZnS quantum dots are obtained. The intensity dependence of two-photon absorption coefficients is presented. The dependence determines the boundary of the influence of high-order nonlinearities on the nonlinear transmittance of the samples. The mechanisms of optical limitation exhibited by sols, specifically, two-photon absorption, nonlinear refraction, and nonlinear scattering are discussed.

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Giant Third-Order Nonlinear Response of Mixed Perovskite Nanocrystals

Materials ◽

10.3390/ma15010389 ◽

2022 ◽

Vol 15 (1) ◽

pp. 389

Author(s):

Aya M. Abu Baker ◽

Ganjaboy S. Boltaev ◽

Mazhar Iqbal ◽

Mikhail Pylnev ◽

Nasser M. Hamdan ◽

...

Keyword(s):

Nonlinear Optical ◽

Laser Pulses ◽

Photon Absorption ◽

Third Order ◽

Central Wavelength ◽

Third Harmonic ◽

Perovskite Nanocrystals ◽

Two Photon Absorption ◽

Two Photon ◽

The Third

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.

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