Flexible passive integrated photonic devices with superior optical and mechanical performance

Abstract

Flexible integrated photonics is a rapidly emerging technology with a wide range of possible applications in the fields of flexible optical interconnects, conformal multiplexing sensing, health monitoring, and biotechnology. One major challenge in developing mechanically flexible integrated photonics is the functional component within an integrated photonic circuit with superior performance. In this work, several essential flexible passive devices for such a circuit were designed and fabricated based on a multi-neutral-axis mechanical design and a monolithic integration technique. The propagation loss of the waveguide is calculated to be 4.2 dB/cm. In addition, we demonstrate a microring resonator, waveguide crossing, multimode interferometer (MMI), and Mach–Zehnder interferometer (MZI) for use at 1.55 µm, each exhibiting superior optical and mechanical performance. These results represent a significant step towards further exploring a complete flexible photonic integrated circuit.

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

“…Thus, the neutral axis can be controlled by changing the thickness of the top and bottom SU-8 coating, which allows evanescent interactions between the optical field and the surrounding environment while showing remarkablemechanical flexibility. [28] Figure 4b plots the strain distribution of the prepared device simulated by the finite element method (FEM) [28,33] with a bending radius of 1.4 mm. The simulation results show that the peak strain at the position of TiO 2 MRR is 0.21%.…”

“…[ 18 ] In addition, thermal evaporation can also be considered a near‐room temperature film deposition technique to fabricate flexible integrated photonic devices directly. [ 12,28,33 ] However, this technique is only limited to materials with low melting points, such as chalcogenide glasses, which cannot be used in biophotonic applications due to the high toxicities of chalcogens. [ 34 ]…”

“…[18] In addition, thermal evaporation can also be considered a near-room temperature film deposition technique to fabricate flexible integrated photonic devices directly. [12,28,33] However, this technique is only limited to materials with low melting points, such as chalcogenide glasses, which cannot be used in biophotonic applications due to the high toxicities of chalcogens. [34] To address these issues, we develop a novel fabrication route for flexible integrated photonic devices using water-soluble germanium oxide (GeO) as the sacrificial layer, which can withstand high annealing temperatures and high-power oxygen plasma, allowing direct integration of inorganic optical materials via different thin-film deposition techniques.…”