Transmission properties of microcoils based on twisted birefringent fibre

We model the linear transmission properties of birefringent optical microcoil resonators (OMRs) by numerically solving polarisation dependent coupled mode equations. When the fibre is twisted, results show spectral bands where strong coupling between the different polarisations occur. The extinction ratio of certain resonances is also found to be enhanced by the exchange of power into another polarisation. Compared to the standard OMR, the choice of fibre twist and level of birefringence provide additional flexibility in tailoring the OMR spectral properties as needed for applications such as filtering, signal processing and sensing.