Fig. 3: Characterization of PNJ head.

a Top view optical microscopic image of cavity with nanoprobe holding a microsphere, ~13 μm diameter as PNJ head. b Front view of the microsphere placed at the cavity opening and near to the nanoprobe. c Beam profiling of photonic nanojet from the microsphere, the white curve indicates microsphere’s boundary. d 3D beam-profile of the nano-jet taken at a selective transverse plane with highest intensity in the PNJ from (c). e Variation in the spot-size, ω over the length of the PNJ. The yellow shaded area lies inside the microsphere. f Transverse beam profiles of the beam from nanoprobe (red triangles) and PNJ (blue solid square) at the plane of the highest intensity.