Tunable Lasing from a Cholesteric Liquid Crystal Film Embedded with a Liquid Crystal Nanopore Network
ABSTRACT 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.
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ABSTRACT: During the past decade, photonic band edge lasers based on cholesteric liquid crystals (CLCs) have attracted considerable interest as self-assembled coherent, tunable lights sources. We report on recent progress towards practical applications: (i) Electrical fine tuning of laser emission by in-plane electric fields: the field-induced distortion of the cholesteric helix allows for a controllable, continuous and reversible shift of the band edge resonances. (ii) Improvement of lasing performance by application of an electric field along the helical axis of a system with negative dielectric anisotropy: the electric field stabilizes the soft photonic structure against heating-induced distortions. (iii) PDMSenclosed LC lasers for lab-on-a-chip applications: We demonstrate the formation of a uniform planar cholesteric texture between polydimethylsiloxane (PDMS) substrates and narrow-band laser emission of a PDMS-enclosed LC laser. With PDMS being the standard material for the fabrication of microfluidic devices, this opens a simple and flexible route for the integration of coherent light sources in lab-on-a-chip designs.Proceedings of SPIE - The International Society for Optical Engineering 03/2013; DOI:10.1117/12.2008373 · 0.20 Impact Factor
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ABSTRACT: Fast (∼10 μs) and deformation-free electro-optic tuning of a liquid crystal is reported, achieved by macroscopic alignment and switching of nanosized, pseudo-nematic domains. The tuning mode can be achieved by photopolymerizing a mesogenic monomer–liquid crystal mixture in the liquid crystal phase, and forming nanosized pores in the polymer matrix. This concept is particularly effective in liquid crystals with spontaneous structure-forming capabilities: here this concept is applied to a cholesteric liquid crystal and demonstrate scatter-free tuning of the Bragg reflection band. It can also lead to new device applications such as thin-film optical amplitude modulators and linear polarization rotators.Advanced Optical Materials 03/2013; 1(3). DOI:10.1002/adom.201200028 · 4.06 Impact Factor
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ABSTRACT: The combination of photoluminescence (PL) and cholesteric liquid crystal (CLC) provides interesting complementary features for an optimized display application. Distortion of the Bragg lattice of CLCs decreases selective reflection but increases fluorescence intensity; recovery of a uniform lattice in turn results in increased reflection and decreased fluorescence. This complementary relationship between the fluorescence and the Bragg reflection gives rise to self-compensations for color shifts due to either dynamic slow response of CLC helix or mismatch of oblique incidence of light with respect to the helical axis. These color shifts have long been intrinsic unsolved limitations of conventional CLC devices. Thus, the complementary coupling between the fluorescence and the CLC Bragg reflections plays an important role in improving the color performance and the quality of moving images.Optics Express 03/2013; 21(5):6243-6248. DOI:10.1364/OE.21.006243 · 3.49 Impact Factor