Unraveling the optomechanical nature of plasmonic trapping

Non-invasive and ultra-accurate optical manipulation of nanometer objects has recently gained a growing interest as a powerful enabling tool in nanotechnology and biophysics. In this context, Self-Induced Back-Action (SIBA) trapping in nano-optical cavities has shown a unique potential for trapping and manipulating nanometer-sized objects under low optical intensities. Yet, the existence of the SIBA effect has that far only been evidenced indirectly through its enhanced trapping performances. In this article we present for the first time a direct experimental evidence of the self-reconfiguration of the optical potential experienced by a nanoparticle trapped in a plasmonic nanocavity. Our observations enable us gaining further understanding of the SIBA mechanism and determine the optimum conditions to boost the performances of SIBA-based nano-optical tweezers.