Enhanced polarisation-independent optical ring resonators on silicon-on-insulator

Recently, we have realised a polarisation independent optical racetrack resonator whose resonant dips for TE and TM align to better than 1pm. The devices had a Free Spectral Range (FSR) of only several hundred picometres. This in large part was to the relatively large bend radius (similar to 400 mu m) designed and fabricated with initial focus on producing low bend loss devices.. Modelling of the bend loss of the same dimension devices shows that the bend radius can be reduced significantly (down to similar to 25 mu m) to produce race track ring resonator with an FSR that is approximately 400% larger than that of those previously fabricated, whilst retaining polarisation independence. This paper will focus on the proposed enhancement of these devices as well as the impetus for their investigation.