Single nanoparticle sensing and waveguide applications using photonic nanojet from an array of shaped microparticles

Abstract

Photonic nanojet (PNJ) is an intense and narrow beam that emerges from the shadow side of a dielectric microparticle. In this work, we have studied the dependence of the PNJ length on the size, shape, refractive index and the number of particles. Four shapes of the particle, namely, elliptical, cubical, circular and triangular have been investigated. Arrays of cubical and elliptical particles have shown the formation of PNJ for array lengths more than 30. Multiple PNJs have been observed for cubical and triangular arrays. The width of the obtained jet can be tuned from μm to nm dimension. The PNJ length increases by a factor of ∼29 when kept in a biofluid. The change in the width of the PNJ observed in presence of a single nanoparticle (NP) can be used as a sensing parameter. The PNJ width of 0.2λ has been obtained in the presence of the NP. The PNJ from an array of microparticles has been found to be useful in the waveguides due to the propagation distances ∼30 times the wavelength.