We report on the third-order nonlinear optical properties of sol-gel prepared CdS quantum dots (with different thermal treatments, filling factors and matrix), and commercial Schott filters (CdSSe nanodots), compared to a bulk CdS crystal. Also PbS quantum dots have been characterised. The spectral dispersion of third-order nonlinear optical response of the samples has been determined by third harmonic generation (THG). By taking into account the dots concentration and appropriate local field correction factor, we have been able to extrapolate a renormalised nonlinear coefficient for the dots, which can be directly compared to the nonlinear coefficient of the forming bulk constituents. In the out-of-resonance regime, no intrinsic enhancement of the nonlinear coefficient due to quantum confinement has been detected for any sample, with respect to the bulk constituent. In particular quantum dots were reported to show enhanced nonlinear optical response when compared to the bulk constituents [1,2], resulting in promising performances in view of applications in all-optical data processing field. This is more evident as quantum dots can be dispersed in a glassy matrix, resulting in composite materials, which in principle can be easily integrated with optical fibers in devices and subsystems for telecommunication applications.However, the interpretation of the experimental results on the enhancement of the nonlinear optical properties of quantum dots is questionable, since in general, different characterization techniques can be used and experimental conditions are not always comparable. Besides, recently a systematic study has been published which doubt this effect of enhancement of nonlinear optical yield in quantum confined systems [3].In this frame we have investigated the third-order nonlinear optical properties of samples of CdS quantum dots, prepared by sol-gel and which differ by matrix, thermal treatments and resulting filling factor (i.e. volume fraction). For a comparison, the same nonlinear characterization was performed also on commercial Schott filters (CdSSe nanodots) and on a sample of bulk CdS crystal. Samples of quantum confined PbS have also been characterised. The third-order nonlinear optical response of the samples has been determined by third harmonic generation (THG). The experimental set-up allows tuning of
In this paper, we will provide a N-to-D analysis able to account for the punctual vs. habitual reading of proper temporal names in Italian, focusing on names of days, which clearly signal a difference in their possible aspectual encoding at the morphosyntactic level. When these items appear as adverbials modifying an event:
i) such event is interpreted as a habitual one if the temporal name is preceded by a definite determiner or an adpositional item;
ii) it is interpreted as a punctual one if the temporal name is ‘bare’.
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