Photocurable Liquid Core–Fugitive Shell Printing of Optical Waveguides

N Integrated optical systems require waveguides that can route light along defi ned pathways with minimal losses and negligible crosstalk. [ 1–3 ] In addition to signal transmission, optical waveguides play an important role in the area of sensing. For example, evanescent fi eld sensors are applied to the detection of analytes in the body, [ 4 ] atmosphere, [ 5 ] and liquid solutions. [ 6 ] Polymeric and hybrid materials are of increasing interest for these applications due to their low temperature processing. [ 7 ] To date, channel waveguides have been fabricated by direct lithographic patterning, [ 8 , 9 ] photoresist-templated etching, [ 10 ] or soft-lithographic approaches. [ 11 , 12 ] However, these techniques are limited either to in-plane confi gurations or require repeated developing or etching steps to produce multiple layers of waveguides. Those processing steps often have a deleterious effect on waveguide performance, leading to rough edges and, hence, higher optical loss. [ 8 , 11 , 13 ]