Effect of interface roughness and polarisation on the optical losses of porous silicon-based waveguides

Optical losses measurements were performed at 1550 nm on both porous silicon (PSi) and oxidised PSi (OPSi) planar waveguides as a function of interface roughness. The PSi waveguides were produced at different anodisation temperatures to reduce the interface roughness. The authors noticed a decrease in optical losses with the diminution of roughness. The lowest value of optical losses was equal to 0.5 dB/cm and obtained for OPSi waveguide with a 10 nm interface roughness and anodisation temperature equal to 20 C. The surface scattering losses were modelled. There is a good agreement between the theoretical and experimental values. The optical losses were also carried out in transverse electric (TE) and transverse magnetic (TM) polarisations for both PSi and oxidised OPSi waveguides.