fig9

Figure 9. Multi-neutral-axis theory^[117]: (A) Cross-sectional schematic of the flexible photonic chip with a PI-silicone-SU8 three-layer structure; (B) Contour plot of bending strain distribution obtained from FEM when the structure is bent; (C) Resonance wavelength shift plotted as a function of bending curvature; Symbols are experimentally measured data, solid lines are predictions made using multi-neutral-axis theory. (A-C) are reprinted with permission from Ref.^[117], Copyright © 2014 Springer Nature. Integrated stretchable photonics^[75]: (D) Top-view micrographs of a stretchable device; (E) normalized optical transmittance spectra of a ChG/SU-8 stretchable resonator at different nominal strain levels; (F) Q-factors of ChG/SU-8 resonator devices before and after 3,000 stretching cycles at 41% nominal strain. (D-F) are reprinted with permission from Ref.^[75], Copyright © 2017 The Author(s). PI: Polyimide; FEM: finite element method; ChG: chalcogenide glass.