Ultralow-Power Electrically Activated Lab-on-a-Chip Plasmonic Tweezers

Abstract

We propose ultralow-power plasmonic tweezers with no external optical source. They consist of a one-dimensional array of graphene-based plasmonic units driven by the optical transitions within the underlying array of $(\mathrm{Al},\mathrm{In})\mathrm{As}/(\mathrm{Ga},\mathrm{In})\mathrm{As}/(\mathrm{Al},\mathrm{In})\mathrm{As}/(\mathrm{Ga},\mathrm{In})\mathrm{As}/(\mathrm{Al},\mathrm{In})\mathrm{As}$ quantum cascaded heterostructures (QCHs), electrically biased in series. Each QCH unit formed in a nanopillar can act as a built-in optical source required for exciting the localized surface plasmons (LSPs) at the surface of the overlying circular graphene nanodisk. The stimulated emission due to intersubband transition within each optical source evanesces through the top $(\mathrm{Al},\mathrm{In})\mathrm{As}$ cladding layer and interacts with the overlying graphene nanodisk, inducing the LSPs required for the formation of the plasmonic tweezers. Numerical simulations show, under 145--170 mV applied voltages, that the tweezers with graphene nanodisks of 16--30 nm in diameter and chemical potentials of 0.5--0.7 eV can trap polystyrene nanoparticles of 9 nm in diameter and larger, demonstrating acceptable sensitivities for variations in the nanoparticle diameter and refractive index. These lab-on-a-chip plasmonic tweezers, benefiting from their small footprints and ultralow power consumptions, which are capable of sensing and trapping nanoparticles without requiring expensive external optical sources, open up a different horizon for developing compact on-chip plasmonic tweezers.