We present new principles underlying optical trapping and manipulation techniques by introducing an additional degree of freedom: the polarization gradient found in evanescent fields. These evanescent fields are common at the micro and nano-scales. When generated by guided modes in integrated waveguides, these evanescent fields exhibit transverse spin and Belinfante momentum. Both of these properties can be harnessed for optical trapping and micromanipulation. Our technique can be integrated with photonic integrated circuits to leverage their rapid construction and widespread deployment. Furthermore, our method complements the existing intensity-gradient and phase-gradient-based optical trapping methodologies. By carefully crafting holographic designs, optical forces rooted in intensity, phase, and polarization gradients can either be selectively produced or synergistically merged. Such advancements pave the way for a broader range of applications for optical tweezers, spurring the discovery of fresh optical manipulation capabilities.

The lead author for this article is Dr Jinsheng Lu, in collaboration with Prof Vincent Ginis, Dr Soon Wei Daniel Lim, and Prof Federico Capasso.

Read the article in Physical Review Letters here or on this website. See the news report from Nature here.