Low-loss photonic wires defined by local oxidation of silicon (LOCOS)

Abstract

We demonstrate low-loss photonic wire waveguides, in both the straight and bent waveguide configurations, fabricated by the LOCal Oxidation of Silicon (LOCOS) process, using the standard optical lithography. The oxidation in the LOCOS process produces waveguides in submicron dimensions with ultra-smooth sidewalls. The Full-Width Half- Maximum (FWHM) of the fabricated LOCOS wire waveguide is approximately 650 nm and the height is 280 nm. We used the cut-back method to measure the propagation loss of the TE (x-polarized) mode. The average propagation loss measured by the cut-back method was 8.78 dB/cm, while the minimum measured propagation loss achieved was 7.18 dB/cm for simple straight waveguides. The propagation loss is expected to be lower, as we include the scattering loss in the measurements. The measured bending loss of the LOCOS wire waveguide with a bending radius of 5 um is as low as 0.0089 dB/90° bend for the TE mode. To the best of knowledge, this is the first direct measurement in propagation loss and bending loss for LOCOS wire waveguides.