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Liquid Crystal Optical Microcavities for Soft Photonics
I. Musevic1,2 and M. Humar1
1 J.Stefan Institute, Jamova 39, Ljubljana
2 Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, Ljubljana

A small droplet of a nematic liquid crystal, embedded in a polymer or liquid matrix, is an optical microresonator, if the index of refraction of a liquid crystal is higher than that of the surrounding. We have shown in a recent publication [1], that the spectrum of light in the nematic liquid crystal microresonator shows characteristic Whispering Gallery Mode structure. In a ray picture, light is circulating inside the microcavity by subsequent total internal reflections at the liquid crystal-surrounding interface. If the light comes back to the point of origin with the same phase, we have the resonance condition for a particular wavelength. We have shown, that the eigenfrequencies of WGMs in a 10-20 m diameter nematic droplet can be tuned by an external electric field. The electric tuning is due to the field-induced elastic deformation of the nematic and is nearly hundred times larger compared to tuning in solid materials. This is interesting for application in integrated photonics, where the microresonators are the basic element for many devices. We demonstrate lasing in liquid crystal microdroplets and we discuss whether integrated soft photonics, based on liquid crystals, could be realized.

[1] M. Humar, M. Ravnik, S. Pajk, I.Musevic, Nature Photon. 3, 595(2009).

"Jožef Stefan" Institute

University of Ljubljana
Faculty of Mathematics
and Physics

Center of Excellence