Gold nanoparticles (AuNPs) are capable of localizing and enhancing light on a nano-sized scale, making these particles a unique structure to overcome the diffraction limit to allow for higher optical resolution in photonic devices. The optical response of AuNPs is controlled by their size, shape, and the refractive index contrast with the surrounding medium. Using phase change materials (PCMs) in the AuNP design introduces a dynamic tunability to the optical response without any modification to the geometrical properties. In this work, we have studied the induced photothermal response of the vesicle nanoparticle (VNP) consisting of a vanadium dioxide (VO2) core (80 nm), as a PCM, and an Au shell (10 nm) covered by Au-seeds (10 nm). When the VNP is irradiated by a CW laser, the light energy absorbed by the particle provides enough heat for the VO2 core to undergo a phase change from the semiconductor state to the metallic state. To do this, we simultaneously solve a selfconsistent multiphysics problem consisting of electromagnetism and thermodynamics. Our calculations show that the maximum tunability of the extinction cross section corresponds to the scattering part achieved at the near-infrared wavelength of λ = 790 nm for the incident threshold intensity of 101.5 kW/cm2 at which the VO2 core experiences the semiconductor-metal phase change. We also show how the temperature is localized inside the VNP at both the semiconductor and metal phases of the VO2 core. It is expected that our results will offer a promising potential application in active photonic devices, near infrared imaging, detectors, and tunable scatterers.
