Generation of long photonic nanojet by a self-assembled microdevice on optical fiber

Photonic nanojet (PNJ) is a narrowly focused and highly concentrated electromagnetic beam that is located on the shadow side of a transparent microdevice. Here we report nanoparticle self-assembled microdevices for PNJ generation. By the self-assembly technology, the microdevice has a controllable shape from a truncated sphere to a spherical segment. Its radius of curvature can be easily adjusted to ∼10 μm by using the Plateau–Rayleigh unstable process. Its refractive index is ∼1.367 in 400 nm to 600 nm waveband. By integrating one of the self-assembled devices on the optical fiber facet, PNJ is generated with long decay length of 72.2μm and working distance of 79.8μm. In the experiment, the fiber-based PNJ exhibits a fluorescence enhancement factor of 9.65.