Abstract
We present a comprehensive theoretical and numerical analysis of the physical mechanisms pertaining to the nonlinear pulsed excitation of optical modes in plasmonic cavities made of metallic nanowires. Our analysis is based on extensive numerical simulations carried out both in the frequency and time domains. The numerical algorithm used in our study is based on the multiple scattering method and allows us to include in our analysis the effects of both the surface and bulk nonlinear polarizations generated at the second harmonic (SH). In particular, we investigate the physical properties of plasmonic modes excited at the SH as the result of the interaction of femtosecond optical pulses with plasmonic nanocavities. We show that such cavities have two distinct types of modes, namely, plasmonic cavity modes and multipole plasmon modes generated via the hybridization of modes of single nanowires. Our analysis reveals that the properties of the latter modes depend only weakly on the cavity geometry, whereas the lifetime and quality factor of plasmonic cavity modes vary considerably with the system parameters.
Highlights
In recent years, we have witnessed a paradigmatic shift in the research methodologies used in studying the physical properties of electromagnetic media
In the presentation of our main results we will focus on the optical properties of the localized modes excited at the second harmonic (SH) as the main conclusions derived in this case apply to the modes observed at the fundamental frequency (FF)
surface plasmon polariton (SPP) modes, such as their Q factor, can be much easier calculated if the optical field at the SH is analyzed. This approach can be relevant for a series of potential technological applications, such as sensing or optical detection, as the optical signal generated at the SH is spectrally well separated from the incoming and scattered fields at the FF
Summary
We have witnessed a paradigmatic shift in the research methodologies used in studying the physical properties of electromagnetic media. One important property of localized SPPs is that their physical properties, such as, resonance frequency, optical loss, field enhancement, are strongly dependent on the geometry and material parameters of the corresponding plasmonic nanostructures. Such, SPPs can be instrumental in designing ultra-compact devices, such as nanolasers or laser arrays [28, 29, 30, 31] and optical microcavities [32, 33, 34, 35] In this connection, a central issue is to devise plasmonic structures which support localized SPPs with low optical losses (modes with large Q factor). The final section summarizes our findings and outlines the main conclusions of our work
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