Investigations on the director field around microdisc resonators

Abstract

The dielectric anisotropy of nematic liquid crystals can be used to achieve electrical tunability of optical whispering-gallery modes in microdisc resonators. In the present study the director field configuration around these microdisc resonators has been investigated using polarising optical microscopy, fluorescence confocal polarising microscopy and theoretical director field calculations. The results show a relationship to the director field around spherical particles with planar anchoring conditions, featuring two boojums and a parallel director orientation along the easy direction of the cell. The influence of electrical fields on the director field is discussed, including its effect on dielectric properties in the vicinity of the disc.

Keywords:

• director fields
• topology
• micro resonators
• lasing

Acknowledgements

The authors wish to thank Dirk Reuter and Andreas D. Wieck for providing the semiconductor quantum dot structures with high luminescence efficiency at room temperature, which enabled the observation of tunable microdisc emission [6–8] which provided the motivation for the present study.

We are grateful for financial support provided by the Deutsche Forschungsgemeinschaft (DFG Research Training Group GRK1464, Micro- and Nanostructures in Optoelectronics and Photonics), the European Science Foundation (EUROCORES programme, Self-organized nanostructures II, LC–NANOP), and by BMBI via grant No. 03X5509.