Ultra-Low Loss Waveguides

As part of IRT Nanoelec, in collaboration with the optical department of LETI (DOPT), we are working on the optimization of manufacturing processes for Si and SiN waveguides with ultra-low losses. By introducing annealing under hydrogen, we reduced the roughness of the side of the Si waveguides (RMS=0.25 nm) and obtained record optical losses on an international scale (<1.1db/cm for STRIP guides and <0.3 db/cm for RIB guides whatever the width of the guides measured at 1310 nm). This know-how was transferred to the photonic platforms of STM and DOPT. For the SiN guides, we have also developed an annealing method to almost completely eliminate residual NH bonds, and thus obtain a record quality factor of 3.106. We also showed that we were able to generate a Kerr-type frequency comb, which is extremely promising for nonlinear optics applications.

a) and c) Images of STRIP and RIB guide profiles after Hydrogen annealing; b) and d) Optical losses of guides at 1310nm as a function of their width :