Optical waveguides on silicon chips

Optical waveguides consisting of a SiOxNy, (0≤x, y≤l) core and SiO₂ cladding layers have been fabricated using Si LSI technologies. Low-pressure chemical vapor deposition (CVD) at 750 °C and remote-plasma CVD at 300 °C have been employed for the deposition of core materials. The propagation loss of ridge type waveguides depends on the size (thickness and width), refractive index and surface roughness of the core. A minimum loss of 1.5 dB/cm has been obtained. Micromirrors made from substrate-Si, poly-Si or Al, which change the light propagation direction, have been fabricated using wet-chemical or chemical dry etching. The light bending efficiency ranges from 60% to 80% depending on the material. Simulations and measurements of the propagation losses of branched and curved waveguides have been carried out. It is shown that the simulated results are in good qualitative agreement with theexperimental data for both branched and curved waveguides. Single-chip integration of light emitting diodes (LEDs), micromirrors, waveguides, and photodetectors has been accomplished and the signal transfer from the LED to the photodetectorhas been verified.