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Emission spectroscopy of NaYF4:Eu nanorods optically trapped by Fresnel lens fibers

The emission of optically trapped NaYF4:Eu nanorods with a high aspect ratio is studied by polarization-resolved spectroscopy with particular emphasis on the magnetic and electric dipole transitions. High trapping efficiency is observed using converging beams, emitted from diffractive Fresnel lenses directly 3D printed onto cleaved fiber facets. Stable nanorod trapping and alignment are reported for a fiber-to-fiber distance of 200 µm and light powers down to 10 mW. The respective σ and π orientation of the different emission lines is determined. The angle with respect to the nanorod axis of the corresponding magnetic and electric dipoles are calculated