Effect of reactive ion etching–generated sidewall roughness on propagation loss of buried‐channel silica waveguides

Different mask materials (photoresist and amorphous silicon) and different sample temperatures can influence the roughness of sidewalls produced during reactive ion etching of silica. Buried‐channel waveguides with different microroughness on the core sidewalls (corrugation periods less than 1 μm) have been fabricated and characterized for their propagation loss at 1.3 μm wavelength. An increase in the sidewall roughness amplitude of around 0.05 μm results in an increase in the propagation loss of 0.2 dB/cm. Sidewall roughness with a larger period appears to have smaller effect on loss.