A Universal Approach to High‐Index‐Contrast Flexible Integrated Photonics

Abstract Flexible integrated photonics is an essential technology for emerging applications, including flexible optical interconnects, optogenetic stimulation, and implantable conformal sensing. Here, a novel and universal route for fabricating flexible photonic components with high‐refractive‐index contrast is reported. Central to such a unique method is the utilization of germanium oxide (GeO) as the sacrificial layer for releasing nanostructures from rigid substrates to flexible substrates. Various high‐quality inorganic optical materials can be grown directly on GeO by different thin‐film deposition methods due to its resistance to both high temperature and high‐power oxygen plasmas. In addition to the absence of restrictions on the material choices and integration processes for flexible photonic structures, the approach uses water as the etchant to remove the sacrificial layer, which has minimal impact on the optical performance of the photonic structures. Using this approach, a strain‐insensitive/sensitive microring resonator based on plasma‐enhanced chemical vapor deposited silicon nitride and reactive sputtered titanium oxide, respectively, is demonstrated, establishing the strategy as a facile and universal route for the fabrication of high‐index‐contrast flexible integrated photonic devices with various functionalities.