Ultrafast photoinduced enhancement of nonlinear optical response in 15-atom gold clusters on indium tin oxide conducting film

Abstract

Abstract:We show that the third order optical nonlinearity of 15-atom gold clusters is significantly enhanced when in contact with indium tin oxide (ITO) conducting film. Open and close aperture z-scan experiments together with non-degenerate pump-probe differential transmission experiments were done using 80 fs laser pulses centered at 395 nm and 790 nm on gold clusters encased inside cyclodextrin cavities. We show that two photon absorption coefficient is enhanced by an order of magnitude as compared to that when the clusters are on pristine glass plate. The enhancement for the nonlinear optical refraction coefficient is ~3 times. The photo-induced excited state absorption using pump-probe experiments at pump wavelength of 395 nm and probe at 790 nm also show an enhancement by an order of magnitude. These results attributed to the excited state energy transfer in the coupled gold cluster-ITO system are different from the enhancement seen so far in charge donor-acceptor complexes and nanoparticle-conjugate polymer composites. 4553-4558 (1983). 4.D. Ricard, P. Roussignol, and C. Flytzanis, "Surface-mediated enhancement of optical phase conjugation in metal colloids," Opt. Lett. 10(10), 511-513 (1985). 5.M. J. Bloemer, J. W. Haus, and P. R. Ashley, "Degenerate four-wave mixing in colloidal gold as a function of particle size," J. Opt. Soc. Am. B 7(5), 790-795 (1990). 6. R. Philip, G. R. Kumar, N. Sandhyarani, and T. Pradeep, "Picosecond optical nonlinearity in monolayer-protected gold, silver and goldsilver alloy nanoclusters," Phys. Rev. B 62(19), 13160-13166 (2000). 7.T

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Novel Bi2O2CO3/polypyrrole/g-C3N4nanocomposites with efficient photocatalytic and nonlinear optical properties

“…69 Similar to nonlinear scattering, the reverse absorption performance originating from PPy and g-C 3 N 4 may also play a role to somewhat for the improved optical nonlinearity, 24,25 though their content is very low in the as-prepared composites. Another possible reason for the enhanced nonlinear optical performance for BP/C0.5 in comparison to those of Bi 2 O 2 CO 3 and BP may be assigned to an intersystem excitation transfer mechanism, typical via the effective charge transfer process, contributes to increasing the free carrier population, 70 and this results in the uorescence quenching and energy releasing, and therefore the limiting action. The effective charge transfer process can be supported by the results of uorescence, photocurrent response and electrochemical impedance experiments ( Fig.…”

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“…GSH indicates glutathione used as the core-etching agent and as the ligand to protect the Au15 core. Adapted from reference [55].…”

“…Time-resolved differential transmission data for the two samples shown on linear-linear scale (c) and log-linear scale (d), taken using 395 nm pump and 790 nm probe pulses to show the difference in the signal magnitude for the two samples and the related carrier relaxation dynamics involving initial thermalization time-constant r, fast and slow decay time-constants 1 and 2, respectively, estimated from fitting the data with bi-exponentially decaying function. Adapted from reference [55].…”

“…Possible excited-state intersystem coupling between Au15 clusters and ITO is represented by the curved arrow and out of many possible interstate relaxation processes few are marked by thin downward arrows. Taken from reference[55].…”