Optical trapping is a widely used technique allowing for remote and precise manipulation of particles and measurement of the forces acting on them. Yet, it has significant limitations when it comes to particles that strongly interact with light e.g. plasmonic and high-index dielectric nanoparticles. These particles have the cross section for the light-matter interaction much larger than their physical size. This makes them perfect nanoantennas for bio-sensing, SERS, local temperature measurements, and heat-therapy. It also allows for efficient transfer of spin and orbital angular momentum of light for realization of fast nanorotors. The same property makes their optical trapping in 3D challenging and limited to a narrow size range due to the strong radiation pressure.
We use a vector beams created using optically anisotropic crystals to optically trap and spin plasmonic nanorods in 3D fashion [1]. Using different configuration of the anisotropic crystals we can create a three dimensional optical vector field for realization of complicated motion and alignment of the trapped nanorod.
We also show that the Raman signal from the optically trapped silicon nanoparticle can be used to determine the internal temperature of nanoparticle. Temperature of the medium outside the nanoparticle can be retrieved form analysis of its stochastic motion. Comparing these two temperatures and including them in the nanoscale thermodynamic calculations, we can obtain information about the interfacial thermal Kapitza resistance, and the temperature and viscosity of the media surrounding the nanoparticle.
[1] P. Karpinski, S. Jones, D. Andren, and M. Kall, Laser Photonics Rev. 2018, 1800139.
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