A team at Toyota Central Research and Development Laboratories Inc. in Nagakute, Japan, has developed a method of fabricating optical waveguides in resin that may lead to the production of three-dimensional optical modules as well as to the automation of fiber construction and packaging. The technique, which the team reported in the Aug. 20 issue of Applied Physics Letters, uses the selective photopolymerization of the resin to write waveguides in the substance along the path of a laser beam.The researchers demonstrated the technique by inserting a graded-index multimode optical fiber into a mixture of two resins. They coupled the fiber to an argon-ion laser that generated 380 mW of 488-nm light, which cured the core of the 20-mm-long waveguide. They then hardened the structure by illuminating it with a UV lamp.The final waveguides displayed a NA of 0.19 and a propagation loss of 1 dB/cm or less at wavelengths of 800 nm to 1 µm.