Optomechanical interaction induced by optical force and photothermal effect in nanoscale plasmomechanical resonator

Abstract

Optomechanics, the fields of the interaction between electromagnetic waves and mechanical oscillators, have been investigated for the fundamental investigation of quantum and classical physics and the application of sensor technologies. Plasmomechanical resonators are promising for nanoscale miniaturization of optomechanical systems, leading to improved sensitivity, enhanced power efficiency, and high spatial resolution. Currently, the physical size of plasmomechanical resonators is limited to a micrometer scale. We demonstrated three plasmomechanical platforms: a full three-dimensional wavelength-scale resonator, smallest-possible resonator, and electrically tunable resonator. First, we focused on the three-dimensional wavelength-scale resonator. The combination of the plasmonic nano-rod antenna and supporting narrow dielectric nano-wall demonstrates both efficient optical excitation and precise detection of the picometer-scale longitudinal mechanical oscillation. Measurement depending on the excitation/detection position, the pump laser power, and the wavelength of light enables analysis of optical control and readout of motion. Optical force induces the longitudinal motion of the plasmomechanical resonator. Increased temperature by the photothermal effects reduced Young's modulus and increased thermoelastic damping, which change the mechanical frequency and quality factor, respectively. Second, we designed and fabricated the smallest system consisting of the bowtie plasmonic antenna and supporting narrow dielectric pillar of overall size far below the wavelength of light. The transverse motion of the resonator interacts with the gap plasmonic mode. The small optical volume below the diffraction limit and the low effective mass of only a few tens of femtogram of the resonator enhance the plasmomechanical interaction. We thus expect the realization of extensive modulation of the mechanical frequency and cooling/amplification with the photothermal effect. Third, we demonstrated a plasmomechanical resonator for the electric control of optomechanical effects. A dimer plasmonic antenna integrated on the electrode-deposited nanobeams demonstrates the electrical modulation and tunable transduction between the optical and mechanical resonance modes. We optically measured both electrically actuated longitudinal and transverse oscillation modes. The simulations show the possibilities for controlling the mechanical frequency and quality factor of the transverse resonance mode.