Nanometer optical trap based on stimulated emission in evanescence of a totally reflected Arago spot
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THE EUROPEAN PHYSICAL JOURNAL E
Regular Article
Nanometer optical trap based on stimulated emission in evanescence of a totally reflected Arago spot Nanometer optical trap for fluorescent nanoparticles Olivier Emile1,a and Janine Emile2 1 2
Universit´e de Rennes 1, Campus de Beaulieu, F-35000 Rennes, France Universit´e de Rennes 1, CNRS IPR UMR 6251, F-35000 Rennes, France Received 1 September 2020 / Received in final form 28 September 2020 / Accepted 28 September 2020 Published online: 23 October 2020 c EDP Sciences / Societ` a Italiana di Fisica / Springer-Verlag GmbH Germany, part of Springer Nature, 2020 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, H. Tabuteau, EPL 129, 58001 (2020)) 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.
1 Introduction Since their first report in 1986 [1,2], optical tweezers have become an exponentially growing technique used in optical manipulation of micrometer to nanometer particles [3– 7]. These particles are trapped at the focal point of a tightly focused by optical gradient forces. Several applications of this non-contact particle manipulation have been considered ranging from movement tracking [8–10], application or detection of small forces [11,12], altering cell membranes [13–15], cells sorting [16–18] and particles manipulation [19–24], to name a few. This last application, which is the most popular one, includes dielectric spheres, viruses, bacteria, organelles, or DNA stands manipulation. Optical tweezers and more generally optical manipulation, because of the tremendous development of nanotechnologies, now face a new challenge, that is extending its application range down to the sub-wavelength and nanometer scales world [25–29]. However, on the one hand, due to light diffraction, optical tweezer trap sizes are limited to a fraction of micrometer [30,31], and, on the other hand, the trapping force diminishes as the third power of the particle diameter [32,33], thus limiting their applications. In order to circumvent these limitations, two main bypaths have been followed. The first one is based on a tight a
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focused beam that is totally reflected on a glass/l
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