Polymer waveguide devices with passive pigtailing: an application of LIGA technology

A combination of precision mechanics and LIGA has been used to realize metallic three-level tools for compression molding of transparent thermoplastic polymers. These tools enable the production of waveguide preforms and fiber positioning grooves in the same process step. In this way, a time-consuming active pigtailing can be avoided because the necessary precision of 1 μm is reached in all dimensions of the tool. A second polymer material, usually a casting resin or optical adhesive, is used as a waveguide core material, immersion medium and to fix the cover plate of the device simultaneously. As a first waveguide component a six-fold array of 4×4 multimode star couplers is presented that has been realized with PMMA and COC substrate materials. After production and qualification of a series of 300 of these devices the average excess loss is found better than 3 dB and the uniformity in the range of 2–3 dB. The main application of this device are optical backplanes for high-speed computers, but the technology allows for many other future components in the tele-and datacom field as well as in sensorics. Two further examples, a waveguide-based flow sensor head and a thermo-opto-optical switch are presented shortly.