Figure 3. Mechanical tuning of a Mach-Zehnder interferometer on an elastic substrate.

(a) When the substrate is compressed with strain beyond a critical value, the silicon waveguide buckles with the PDMS substrate. (b) Under increasing compression, the interference fringes in the output of MZI continuously shift toward shorter wavelengths. When the compression is relaxed, the fringes recover to their initial spectral positions. (c) At given wavelengths (1550 nm, blue; 1564 nm, red), the measured transmission (symbols) varies sinusoidally with the increasing compressive strain, in good agreement with the results of the theoretical model (lines). (d) The peak wavelengths (symbols) of the interference fringes shift linearly with the increasing compressive strain toward shorter wavelengths as expected from the theory (lines).