Direct fabrication of silicon photonic devices on a flexible platform and its application for strain sensing.

We demonstrate a process to fabricate silicon photonic devices directly on a plastic film which is both flexible and transparent. This process allows the integration of complex structures on plastic films without the need of transferring from another substrate. Waveguides, grating couplers, and microring resonators are fabricated and optically characterized. An optical strain sensor is shown as an application using 5 µm-radius microring resonators on the flexible substrate. When strain is applied, resonance wavelength shifts of the microring resonators are observed. Contributions of different effects are analyzed and evaluated. Finally, we measure the influence of residual strain and confirm the material undergoes elastic deformation within the applied strain range.