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Abstract
Continuous tuning of lasing wavelength is demonstrated using a photopolymerized cholesteric liquid crystal film embedded with nano-sized liquid crystal droplets. The film is fabricated simply by irradiating ultraviolet light on a mixture comprising photopolymerizable and non-photopolymerizable cholesteric liquid crystals. Because the droplets are smaller than the wavelength of light, they do not contribute to scattering but only to the effective refractive index of the composite: tuning of the lasing wavelength is achieved by applying a field to reorient the liquid crystal molecules in the droplets, thus changing its refractive index. These electro-tunable films also show fast tuning properties and improved thermal stability, making them potentially useful to realize ultra-compact, tunable dye lasers.
Acknowledgments
This work was supported by a Grant-in-Aid from Research Fellowships of the Japan Society for the Promotion of Science for Young Scientists (A228590), a Grant-in-Aid from JSPS and RFBR under the Japan-Russia Research Cooperative Program (J101002026), and a Grant-in-Aid from the Osaka University Global Center of Excellence (GCOE) Program. H.Y. acknowledges support from the JST PRESTO Program. The authors thank Dr. S. Shoji and Prof. S. Kawata of Osaka University for allowing us to use the supercritical rinser, Prof. H. Katayama of Osaka University for allowing us to use the SEM, and Merck KGaA for providing the photo polymerizable ChLC mixture.
