Continuous tuning of lasing wavelength is achieved in cholesteric liquid crystal lasers by embedding a network of nanopores with an average size of 10 nm filled with liquid crystals inside a polymerized matrix with helical order. The device possesses both high transparency and a fast response time because the tuning is driven by local reorientation of the liquid crystal molecules in the nanopores.
In this paper, we report the improved lasing threshold in cholesteric liquid crystal (ChLC) lasers using an in-plane helix alignment, where the helix axis lies in the in-plane direction of the cell. The in-plane helix alignment of ChLCs was obtained by applying an in-plane electric field in a cell with homeotropic surface treatment while cooling the sample from the isotropic phase. The energy threshold of this device was 0.3 mJ/(cm 2 Ápulse), which was found to be less than 1/35 that of conventional planarly aligned ChLC lasers.
We report tunable single-mode lasing with an improved slope efficiency from a cholesteric liquid crystal (ChLC) cavity with a three-layered structure. The device consists of one photopolymerized ChLC layer with a wide reflection band, another ChLC layer with a notch reflection band and a Rhodamine-6G-doped ionic liquid layer acting as the gain medium. Single-mode lasing can be obtained in this device structure because the ChLC layer with the notch reflection band strongly reflects only one of the Fabry-Perot cavity modes. Tuning of the lasing wavelength is achieved by tuning the reflection band of the notch ChLC. The device showed a maximum slope efficiency of 16%, which was found to be approximately 1.5 times larger than that of ordinary ChLC lasers doped with the pyrromethene 597 laser dye.
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