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Size Dependence of the Third-Order Optical Nonlinear Susceptibility of PbS Nanocrystals in PVA

“…The increase of the forbidden energy band gap E g with decrease in the particle size (for PbS, it is less than 18 nm [7]) induces the quantum size effect. However our results showed that, when the size of particles is less than the PbS Bohr exciton radius (about 21 nm [3]), v (3) (x) was not increased, as was predicted in [2], but decreased. The double decrease of the PbS particle size from 18 to 9 nm leads to the three-time decrease of v (3) (x).…”

“…Earlier, it was shown in [3] at k ¼ 532 nm and in [9] at k ¼ 780 nm by means of the Z-scan technique that, in 5-nm PbS NCs, the nonlinear change of the refractive index is negative (n 2 < 0).…”

“…It was experimentally shown [1] that the use of semiconductor nanoparticles in composite materials leads to an increase in the NLO sensitivity. The theoretical calculations [2] showed that, under some conditions, the third-order optical nonlinear susceptibility v (3) (x) is proportional to (1=R) 3 , where R is the crystallite radius. That is, a decrease in the particle size leads to a strong increase in the nonlinear susceptibility.…”

“…That is, a decrease in the particle size leads to a strong increase in the nonlinear susceptibility. It was also shown [3,4] that the third-order optical nonlinear susceptibility v (3) (x) in the visual spectral range in the composites with nanocrystals of narrow-band semiconductors can be much higher than that for wide-band ones. It should be noted that, from the practical point of view, NLO devices based on such materials have to work with widespread lasers Nd:YAG (k ¼ 1064 nm) and Al 2 O 3 :Ti (k ¼ 800 nm).…”

The Peculiarities of Photopolymerization in the Composite “Pre-polymer–TiO2Nanoparticles”

“…[4], oriented arrays of metallic nanoparticles in polymer matrices may be used as color filters for polarized light. Third, the organic films doped with metallic or semiconductor nanoparticles are perspective materials for non-linear optics and associated applications [5][6][7][8]. At last, optical properties of nanoparticle doped polymers determine performance of polymer -nanoparticles -liquid crystal (LC) composites working in electrically controlled light scattering mode promising for display technologies [9].…”