The optical damage behaviour of different LiNbO 3 optical waveguides has been experimentally studied by measuring the intensity output of a single beam as a function of the intensity input. Parallel measurements of photovoltaic currents have been carried out as a function of the input intensity and they have been correlated with the optical damage data. The following LiNbO 3 guides have been studied and compared: proton exchanged (PE) belonging to the phases α, β 1 , β 2 and reverse proton exchanged (RPE) and Zn in-diffused waveguides. The greatest intensity thresholds for optical damage, about 2x10 3 times greater than that of the substrate, have been obtained in RPE guides (they support ordinary polarization and have similar nonlinear optic activity as the substrate) and β 2 guides which support extraordinary polarization (they have no nonlinear optic activity). On the other hand, the lowest photovoltaic currents have been measured in β 1,2 -phases. As a function of the light intensity, the photovoltaic current exhibits a superlinear behaviour, strong in α-phase and weaker in Zn in-diffused and RPE guides. The results for optical damage are discussed in connection with those of photovoltaic currents, paying particular attention to the main mechanisms involved.
Dispersion stability of tin(IV) oxide nanoparticles dispersed in N-Methy-2-Pyrrolidone (NMP), dimethylformamide (DMF) and distilled water assisted by ultrasonication was investigated, aiming to identify a suitable liquid medium to effectively disperse tin(IV) oxide for many useful applications. The dispersions’ stability was characterized using field emission scanning electron microscopy, ultraviolet–visible spectroscopy and Zeta potential. The results show that distilled water has the highest stability with optimum sonication of 1 h. NMP shows better stability and consistency than DMF at different sonication timings. Good agreement between ultraviolet–visible absorbance and Zeta potentials shows that both distilled water and NMP are good mediums to produce highly stable tin(V) oxide dispersion.
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