Zinctetraphenyporphyrine and Au nanoparticle-based nanocomposites (Au-ZnTPP) are examined for their nonlinear optical (NLO) behaviour and optical limiting property using z-scan experiment aiding pulsed laser that delivers 7ns pulses at 532 nm wavelength. The pulsed laser ablation on Au target in ZnTPP is the method of synthesis used for the nanocomposite preparation. ZnTPP with Au nanocomposite formation is confirmed from the quenching of the fluorescent emission spectrum and the modification of absorption spectrum. The introduction of the metal nanoparticle opens up additional energy transfer pathways, that can lead to enhanced excited-state absorption. Moreover, the augmentation is aided by local field effects of the Au NPs, contributes to increased interaction field strength on the surface of the NPs and the surrounding environment of the nanoparticle. The excited state absorption is revealed to be the major mechanism behind the observed nonlinear absorption and optical limiting activity. It is revealed that the suggested method could lead to the implementation of optical limiting-based devices suitable for photonic applications.
Silver nanoparticles were prepared by pulsed laser ablation technique using a second harmonic wavelength (532 nm) of Q switched Nd:YAG laser of 7 ns pulse width and 10 Hz repetition rates. Formation of Ag NPs was confirmed from characteristic surface Plasmon resonance induced absorption (~418 nm). Spherical shape morphology and crystalline nature of structure were revealed from SEM and TEM analysis. Nonlinear optical studies were conducted by z scan analysis with the same laser system used for ablation. A switching of nonlinear absorption (saturable absorption to reverse saturable absorption) in Ag NPs were observed when on axis input intensity increased from 0.27 GW/cm2 to 0.83 GW/cm2 and it could be attributed to interplay of different nonlinear absorption mechanisms, that is strongly depends on the intensity of the excitation source. Self-defocusing nature of the sample was revealed from the closed aperture z scan analysis.
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