Abstract
Abstract The ultrafast concentration of electromagnetic energy in nanoscale volumes is one of the key features of optical nanoantennas illuminated at their surface plasmon resonances. Here, we drive the insulator to metal phase transition in vanadium dioxide (VO2) using a laser-induced pumping effect obtained by positioning a single gold nanoantenna in proximity to a VO2 thermochromic material. We explore how the geometry of the single nanoantenna affects the size and permittivity of the nanometer-scale VO2 regions featuring phase transition under different pumping conditions. The results reveal that a higher VO2 phase transition effect is obtained for pumping of the longitudinal or transversal localized surface plasmon depending on the antenna length. This characterization is of paramount importance since the single nanoantennas are the building blocks of many plasmonic nanosystems. Finally, we demonstrate the picosecond dynamics of the VO2 phase transition characterizing this system, useful for the realization of fast nano-switches. Our work shows that it is possible to miniaturize the hybrid plasmonic-VO2 system down to the single-antenna level, still maintaining a controllable behavior, fast picosecond dynamics, and the features characterizing its optical and thermal response.
Highlights
Plasmonic single nanoantennas have intrigued vast interest due to their various exceptional properties [1,2,3,4,5]
The results reveal that a higher VO2 phase transition effect is obtained for pumping of the longitudinal or transversal localized surface plasmon depending on the antenna length
The value of (−ΔT/T)spatial modulation microscopy (SMM) of around 10−2 signifies that the presence of the antenna results in a reduction of the transmission of 1% compared to the bare VO2 film
Summary
Plasmonic single nanoantennas have intrigued vast interest due to their various exceptional properties [1,2,3,4,5]. Excited by an electromagnetic wave that falls within the antenna’s plasmonic resonance band, the electrons around the surface of this nanostructure are driven collectively to form localized charge density oscillations, so-called surface plasmons, with the same frequency of the electromagnetic wave [6, 7] During this process, the energy of the excitation wave is efficiently transferred into these localized surface plasmons (LSP), leading to a strong field enhancement at the surface of the nanoantenna, which is usually subwavelength sized [8,9,10]. Materials undergoing structural and/or electronic phase transitions as a response to an external stimulus [19,20,21,22,23], such as, for instance, a magnetic field, a light pulse, or direct heating, show a considerable change in their dielectric properties This feature has been very successfully exploited to achieve large optical modulation contrast in nanophotonic switching devices [24,25,26]. Vanadium dioxide (VO2) is characterized by a reversible insulator-to-metal transition (IMT), taking place around a critical temperature of 68 °C [27] and making it a promising
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