Fabrication of subwavelength-structured hollow waveguide array by two-photon polymerization

The fabrication of a subwavelength-structured hollow waveguide array is discussed. We employ a two-photon polymerization process to generate a negative sample of the target structure in a photo polymerizable resin. After developing the resin, gold is electrodeposited into the lithographically opened areas to fabricate the metallic structure. A free standing metallic hollow waveguide array is achieved by removing the unexposed resin. The complete array consists of around 1000 x 2000 subwavelength hollow waveguides with a dimension of 600 nm x 800 nm and a height of 2.9 µm. The free-standing metallic structure features an aspect ratio of 1:10. The hollow waveguide array provides a phase shift between the vertical and horizontal mode and may thus be used as a polarization-converting element.