Increasing telecom traffic has created a great demand for photonic devices with large capacity, small footprint, and high functionality. Novel technologies to manipulate lightwaves more flexibly are highly desired in order to meet this demand. A spatial planar optical circuit (SPOC) is an innovative optical platform that integrates free space optics (FSO) with optical waveguides. This platform brings out the advantages of both the optical waveguides and FSO. We are trying to overcome the limitations of conventional photonic devices by using the SPOC platform (Fig. 1).
Generally, waveguides can be densely integrated in an optical circuit on the two-dimensional plane. On the other hand, FSO can parallelize an optical circuit in three-dimensional space on a massive scale. Figure 2 shows a schematic of the SPOC platform. The SPOC technique combines the advantages of both the waveguide and FSO, which enables us to realize high-performance optical devices. In addition, the optical functions of SPOCs can be reconfigured flexibly by controlling the optical wavefront with a spatial light modulator (SLM).
In our research group, we apply the SPOC technique to photonic node devices. The large capacity and high degree of integration of SPOCs allow us to develop photonic node devices with ultra-high-capacity, which is several hundred times larger than that of waveguide-based ones. In addition, the functions of SPOC-based node device can be dynamically reconfigured by utilizing their high flexibility and variable functionality (Fig. 3). We contribute to advancing the ICT infrastructure to make the most of big-data technology by realizing ultra-high-capacity photonic networks.