Nanometer optical trap based on stimulated emission in evanescence of a totally reflected Arago spot

Abstract

Optical tweezers have paved the way towards the manipulation of particles and living cells at the micrometer range. Its extension towards the nanometer world may create unprecedented potentialities in many areas of science. Following a letter [O. Emile, J. Emile, and H. Tabuteau, EPL 129 (2020) 58001] that reported the observation of the trapping of a single 200-nm-diameter fluorescent particle in a nanometric volume, we detail here our experimental findings. In particular, the trapping mechanism is shown to be based on the radiation pressure of light in one direction and on the stimulated emission of the particle in the evanescent wave of a nanometer Arago spot on a glass/liquid interface on the other directions. The trapping volume is a 200-nm-height cylinder whose radius varies with the spreading of the evanescent wave near the spot and can reach 50 nm. The calculation of the force and the parameters limiting the lifetime are detailed. Applications to laser trapping of atoms and molecules are also discussed.

The Arago–Poisson Spot: New Applications for an Old Concept

“…In order to get around these problems, we therefore proposed the following experimental set-up (see Figure 9) [27,95]. The blue light from a laser (λ = 488 nm) impinges on a glass lamella (e = 170 µm) with an occulting disk deposited on the top of the glass (i.e., oriented towards the laser), leading to an Arago-Poisson spot that propagates through the glass and then into a colloid suspension in demineralized water (see [95] for more details). The particles are monodisperse fluorescent polystyrene spheres (Molecular Probes, diameter 200 nm).…”

Nano-particle transport and the prediction of a valid area to be trapped based on a plasmonic antenna array

“…This also may damage the biological cell or specimen due to the heat generated by large incident power. 6,7 As the metal surface plasmon resonance structures with localized strong gradient electric elds can be used to optically trap nanoparticles, [8][9][10][11][12][13] many groups have focused on the optical trapping for a long time. [14][15][16] The optical force on the nanoparticles caused by the evanescent eld can draw the nanoparticles into a 'hot spot'.…”