Planar-integrated free-space optics with high efficiency

Planar-integrated free-space optical (PIFSO) systems have been in the center of the research at the ONT group for about 10 years. During that time, we could demonstrate the viability of this approach to build optical microsystems for applications in optical interconnection and sensing. An essential step towards practicality is now being taken, namely, the design and fabrication of systems with high efficiency. Conventional lithographic fabrication has been used until recently to implement the optical elements as DOEs (diffractive optical elements). This approach offers very high design flexibility, but it is limited with regard to the achievable efficiency in such cases where large deflection angles are required. As a result, the DOE technology has allowed us to implement a variety of systems demonstrators. In order to make the PIFSO concept useful for real-world applications, we are now investigating suitable fabrication technologies that allow one to implement the elements as ROEs (reflective or refractive optical elements). The following approaches are being investigated: