Figure 2. Preserved optical functionalities of silicon photonic circuits on PDMS substrate.
(a) The transmission spectra of the MZI circuit measured at its two output ports, showing high extinction ratio and complementary interference fringes. (b) Transmission spectra of the micro-ring ADF measured at the “through” and “drop” ports, also showing complementary resonance peaks. (c) Broadband transmission spectrum of a ring resonator critically coupled to a waveguide on the PDMS substrate, showing a high extinction ratio up to 25 dB. (d) Measured high-Q resonance (blue symbols) and Lorentzian fitting (red line) of a transferred ring resonator with a loaded quality factor of 9.9×104 and an intrinsic quality factor of 1.5×105. The corresponding value of propagation loss in the waveguide is 3.8 dB/cm.