Optically controlled elastic microcavities

Whispering gallery mode (WGM) resonators made from dielectrics like glass or polymers have outstanding optical properties like huge cavity quality (Q) factors which can be achieved on scales compatible with on-chip integration. However, tunability of these resonances is typically difficult to achieve or not suitable for robust device applications. We report here on the fabrication of polymeric micro-goblet WGM resonators with an optically controlled and stable reversible tunability over a large spectral range. This tunability is achieved by integration of photo-responsive liquid crystalline elastomers (LCEs) into micro-goblet cavities. The optical response of the elastomer allows reshaping the goblet by employing low pump power, leading to a fully reversible tuning of the modes. The structure can be realistically implemented in on-chip devices, combining the ultra-high Q factors, typical of WGM resonators, with reliable, optical tunability. This result serves as an example of how light can control light, by invoking a physical reshaping of the structure. This way of optical tuning creates interesting possibilities for all-optical control in circuits, enabling interaction between signal and control beams and the realization of self-tuning cavities.