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We report here on the control of remote surface-plasmon-mediated two-photon-induced luminescence of dendritic silver nanoparticle aggregates as observed by femtosecond laser microscopy. With a focal spot diameter approximately 1 microm, polarized remote emission has been observed 99 microm from the focal spot. We show control over the regions of emission by changing the polarization of the incident beam and by changing the spectral phase of the laser pulse.

In this paper, we present a detailed study of localized two-photon photoluminescence from metal nanoparticles on a dielectric surface. An ultrafast (∼13 fs) near-infrared laser focused on a micrometer sized region is used to excite a silver nanoparticle covered quartz or mica substrate, and a pulse shaper is used to control and change the spectral phase of the excitation pulse, as well as allow for autocorrelation-type measurements. Spectra of the observed photoluminescence from individual localized regions remote from the focal spot are obtained. The spatial distribution of nonlinear photoluminescence is found to have characteristics very distinct from that of normal scatter. It is found that the excitation pulse propagates to the different remote regions by means of surface plasmon polariton (SPP) propagation. As the SPP propagates it accumulates different amounts of quadratic and cubic dispersion depending on the path taken. The quadratic and cubic dispersion for a number of such pathways is measured, and evidence of negative dispersion is observed. Photoluminescence is observed at locations where constructive interference and a localized resonance occurs, tens of micrometers from the incident laser pulse.

We describe here an activity that enables students to visualize the dissolution process, ion mobility, and precipitation on a microscale level, all in 30 s. A small puddle of water consisting of approximately 10 drops is placed on a plastic sheet cover. Two small crystals of water-soluble salts are transferred by toothpicks and simultaneously introduced to the puddle from opposite sides. Within 30 s, a precipitate forms where the two ionic solutions meet and the result usually looks somewhat like a cat’s eye marble. A significant feature of this activity is that it uses a minimum amount of resources.

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