Fig. 1

Illustration of the 3D nanoprinted square-core hollow-core waveguide (light blue) interfaced with a commercially available polarization-maintaining fiber (light green) and used for nanoparticle tracking analysis. The magenta elements indicate the nanoparticles that are diffusing inside the core of the waveguide and illuminated by the core mode (green). The yellow volume shows the light scattered by a nanoparticle and captured by the microscope (gray). The inset shows an example of a measured longitudinal trajectory of a selected gold nanosphere diffusing inside the waveguide core