Project duration: 2019/2 – 2020/1
Due to the increasing demand for higher data rates and longer transmission distances, the industry is striving for mono-mode optics, in which only a single light mode is required for data transmission and which represents a significant improvement on the current infrastructure. However, the micro-optics required to couple photonic integrated circuits (PICs) with optical fibers are only a few millimeters in size and require extreme precision in both manufacturing and assembly. This makes them a significant cost factor: fiber coupling accounts for up to 50 percent of total manufacturing costs.
As part of the research project "EFFICIENTlight - Efficient fiber-PIC coupling using wafer-scale glass molding", the project partners developed a new process for the efficient, economically attractive manufacturing of fiber couplers using replicative glass molding at wafer level. For the production of the fiber couplers, the project team reinterpreted various glass molding technologies at wafer level. With the wafer level process, several optics can be manufactured in a single step, which massively reduces production costs. Molding additionally allows the production of complex-shaped optics and expands the design freedom in optics design. These options were exploited in the project: the research team optimized the design of the couplers, for example by integrating multiple optically active surfaces such as lenses and mirrors.
To manufacture the new optical design, the Fraunhofer IPT further developed glass forming technologies and redesigned the processes. In addition to the isothermal process of precision molding, in which glass blanks are heated and molded directly in a forming machine, the more efficient non-isothermal glass forming process was also investigated, in which the material is brought to the required temperature in advance outside the machine. Since the apertures of the micro-optics are only a few 100 µm and have to be introduced with high precision, the process development was very demanding.
Suitability for series production tested in an industrial environment
To demonstrate the suitability of the manufacturing processes for series production under industrial conditions, the processes were carried out on commercial production equipment. The manufactured optics were then assembled and tested in a near-application test environment using circuits developed in-house. The tests showed that the optics fabricated using the newly designed wafer-level isothermal forming process were consistently of the highest quality. The new design of the fiber couplers was also convincing: the optical properties even exceeded expectations in some cases.
Building on the positive results of the "EFFICIENTlight" project, it is planned to further develop both precision molding and non-isothermal forming in the future for the cost-effective production of complex micro-optics in high volumes.