Photonic nanojets generated by microfabricated dielectric cylinders using proton beam writing

Abstract

Photonic nanojet (PNJ) is an optical phenomenon that focuses incident light to a sub-wavelength beam waist/width and several wavelength long beam length by scattering with a microstructure. Here, we report on the PNJs directly generated along the axial axis of poly(methyl methacrylate) (PMMA) micro-cylinders of 2, 4, 6, and 8 μm diameters fabricated by proton beam writing approach. Experimental results reveal that the PMMA micro-cylinders were produced with smooth surfaces, which are appropriate to form the PNJs. Accordingly, the PNJs were measured by using an in-house confocal microscope apparatus. The results show that the larger micro-cylinder diameters led to wider and longer PNJs, which agree well with the finite-difference time-domain simulation. This fabrication of micro-cylinders could offer specific PNJ properties for advancing sub-wavelength applications.