Selective modulation of plasmonic circular dichroism spectra achieved by synergy of asymmetric optomechanical and photothermal effects in nano-plasmonic chiral structures

Nano-plasmonic chiral structures exhibit stronger plasmonic circular dichroism than most organic materials. In addition to the circular dichroism response, the interaction between light and nano-plasmonic chiral structure also involves the photothermal and optomechanical effects. However, the synergy between the photothermal and optomechanical effects under circularly polarized light excitation remains poorly understood. This work investigates the synergy of the photothermal and optomechanical effects in chiral gold nanorod trimers. The asymmetric photothermal and optomechanical effects in gold nanorod trimers with adjacent homochiral centers are analyzed by finite element simulation. The simulation results show that the dynamic structure of the chiral gold nanorod trimer is activated when the photothermal temperature reaches the threshold value. At the same time, the asymmetric optical torque generated by left- and right-handed circularly polarized light will lead to asymmetric changes in the geometry of the gold nanorod trimer, especially in the twist angle of the chiral center, so that the spectral response of the gold nanorod trimer is polarization-dependent. More significantly, based on the synergy of the photothermal and optomechanical effects, experimental results show that the chiral gold nanorod oligomers can be used to control the asymmetric enhancement and suppression of the plasmonic circular dichroic spectral response through the enantioselective interaction of left- and right-handed circularly polarized light. This study provides an important reference for designing advanced nano-photonics devices.