Planar-integrated free-space optics: an integration technique for 3D microoptics

Microoptics and integrated optics are becoming viable technologies for many applications in optical communications, storage, sensing and processing. Both waveguide and free-space optical techniques are of interest. Here, we consider three-dimensional, or: free-space optics. The use of the third spatial dimension is used for imaging, for non-contact probing and sensing and also for high-density optical interconnection in computers and switching systems. Different integration concepts for 3D optics have been suggested: the stacked approach, the planar approach and the micromechanical approach. The stacked approach is can be viewed as a miniaturized version of conventional 3D optics. The micromechanical approach is based on the capabilities to fabricate hinges and stages in an integrated fashion on a silicon wafer. Here, we discuss the concept and applications of planar integrated free-space optics, short: PIFSO. Here, the concept is to fold a 3D optical setup into a 2D geometry in order to be compatible with planar fabrication techniques.