Nonlinear signal even from a single molecule becomes visible at hot spots of plasmonic nanoparticles. In these structures, Fano resonances can control the nonlinear response in two ways. (i) A linear Fano resonance can enhance the hot spot field, resulting enhanced nonlinear signal. (ii) A nonlinear Fano resonance can enhance the nonlinear signal without enhancing the hot spot. In this study, we compare the enhancement of second harmonic signal at the steady-state obtained via these two methods. Since we are interested in the steady-state signal, we adapt a linear enhancement which works at the steady-state. This is different than the dark-hot resonances that appears in the transparency window due to enhanced plasmon lifetime.
Control of the nonlinear response of nanostructures via path interference effects, i.e., Fano resonances, has been studied extensively. In such studies, a frequency conversion process takes place near a hot spot. Here, we study the case where the frequency conversion process takes place along the body of a nonlinear crystal. Metal nanoparticle–quantum emitter dimers control the down-conversion process, taking place throughout the crystal body, via introducing interfering conversion paths. Dimers behave as interaction centers. We show that two orders of magnitude enhancement is possible, on top of the enhancement due to localization effects. That is, this factor multiplies the enhancement taking place due to the field localization.
We propose a miniaturized photonic switch, which utilizes (recently discovered) plasmon analog of index enhancement. An index is tuned via a control (auxiliary) pulse. The operation principle of the proposed device, composed of a few layers of nanorod dimers, is different than the conventional photonic switches. In the proposed device, a stop band is created at the desired frequency determined by the control pulse frequency. Calculated modulation depths are quite large, and response time is determined by the plasmon lifetime. The method we propose here is based on linear operation that requires low power and has very small foot-print that satisfies the major needs to be the choice of a switching scheme for integrated optics.
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