Mirrorless Lasing and Energy Transfer in Cholesteric Liquid Crystals Doped with Laser Dyes

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Abstract
Lasing in cholesteric liquid crystal (CLC) films doped with a mixture of laser dyes has been observed under UV excitation with 35ps pulses at 355nm. To probe optical interactions between molecules of different species, the emission and excitation spectra of the constituents have been studied in the 300–700nm range. Two dyes, a Benzofuran and an Oxazine dye were used in the system under study. Energy transfer between the host CLC and the dissolved dyes occurs, in agreement with previous observations. In addition, spectroscopic data indicates that active energy transfer from the host CLC to the Benzofuran dye, and from the Benzofuran dye to the Oxazine dye plays an important role in lasing in these systems. The Benzofuran dye acts as an impedance transformer, facilitating energy transfer from the host CLC to the lasing Oxazine dye.