Distributed feedback lasing in cellulose films

Wenzlik, Daniel; Varanytsia, Andrii; Muñoz, Antonio; Kósa, T.; Taheri, Bahman; Zentel, Rudolf; Palffy‐Muhoray, Peter

doi:10.1364/ome.4.000162

Cited by 10 publications

(4 citation statements)

References 17 publications

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“…Moreover, due to the helical internal structure, the reflected light is circularly polarized with the same handedness as the helix (Dumanli et al, 2014;Lagerwall et al, 2014;Park et al, 2014). These photonic films have immediate application potential in many photonic materials and devices, e.g., in security papers for anti-counterfeiting purposes (Tabor et al, 2012), sensors (Giese et al, 2013a;Zhang et al, 2013), or in mirrorless lasing (Lagerwall et al, 2014;Wenzlik et al, 2014). Further enhancements are possible by letting the liquid crystalline order organize guest nanoparticles Liu et al, 2014;Nguyen et al, 2014;Querejeta-Fernandez et al, 2014) or template an inorganic or other organic phase that is synthesized within the polysaccharide suspension (Shopsowitz et al, 2010(Shopsowitz et al, , 2012a(Shopsowitz et al, ,b, 2014Kelly et al, 2012;Giese et al, 2013b;Khan et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Equilibrium Liquid Crystal Phase Diagrams and Detection of Kinetic Arrest in Cellulose Nanocrystal Suspensions

et al. 2016

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The cholesteric liquid crystal self-assembly of water-suspended cellulose nanocrystal (CNC) into a helical arrangement was observed already more than 20 years ago, and the phenomenon was used to produce iridescent solid films by evaporating the solvent or via sol-gel processing. Yet, it remains challenging to produce optically uniform films and to control the pitch reproducibly, reflecting the complexity of the three-stage drying process that is followed in preparing the films. An equilibrium liquid crystal phase formation stage is followed by a non-equilibrium kinetic arrest, which in turn is followed by structural collapse as the remaining solvent is evaporated. Here, we focus on the first of these stages, combining a set of systematic rheology and polarizing optics experiments with computer simulations to establish a detailed phase diagram of aqueous CNC suspensions with two different values of the surface charge, up to the concentration where kinetic arrest sets in. We also study the effect of varying ionic strength of the solvent. Within the cholesteric phase regime, we measure the equilibrium helical pitch as a function of the same parameters. We report a hitherto unnoticed change in character of the isotropic-cholesteric transition at increasing ionic strength, with a continuous weakening of the first-order character up to the point where phase coexistence is difficult to detect macroscopically due to substantial critical fluctuations.

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Section: Introductionmentioning

confidence: 99%

Equilibrium Liquid Crystal Phase Diagrams and Detection of Kinetic Arrest in Cellulose Nanocrystal Suspensions

et al. 2016

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“…for optical encryption, 7 or in liquid crystal-based tunable lasers. [8][9][10][11][12][13][14][15][16][17][18] An interesting example is the case of spherical liquid crystal samples, 9,14 i.e. a cholesteric brought into droplet or shell morphology as a component of an emulsion.…”

Section: Introductionmentioning

confidence: 99%

Dynamic and complex optical patterns from colloids of cholesteric liquid crystal droplets

Noh¹,

Drevenšek‐Olenik

Yamamoto

et al. 2015

SPIE Proceedings

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Drops or shells of a planar-aligned short-pitch cholesteric liquid crystal exhibit unique optical properties due to the combination of Bragg reflection in the cholesteric helix and a radial orientation of the helix axis. If such a droplet is illuminated from above, light is reflected into a continuous set of cones, the opening angles of which depend on where on the droplet the light hits its surface. For the wavelength that fulfills the Bragg condition the reflection is dramatically enhanced, yielding the light cones colored. A photonic cross communication scheme arises for certain angles, reflecting light back to the observer from a different droplet than the one originally illuminated. This gives rise to an intricate pattern of colored and circularly polarized spots. A number of interesting applications may be developed based on this pattern, e.g. in identification and authentication devices. We have carried out a detailed spectrophotometric analysis of the patterns, localized to individual spot maxima. A quantitative comparison between the measured spectra and the reflection wavelength expected from a model for the pattern generation allows us to conclude that the droplets are in fact not spherical but slightly ellipsoidal.

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“…Principal attempts refer the use of solvents that can undergo polymerization and also the use of UV sensitive substituents [15,16,17,18]. Lasing in solid cross-linked cholesteric cellulose based films with high reflectivity doped with fluorescent dyes was also recently evidenced in literature [19]. The fabrication of cellulosic spheres by microfluidics, with iridescence was also described in literature [20].…”

Section: Introductionmentioning

confidence: 99%

From Cellulosic Based Liquid Crystalline Sheared Solutions to 1D and 2D Soft Materials

2014

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Liquid crystalline cellulosic-based solutions described by distinctive properties are at the origin of different kinds of multifunctional materials with unique characteristics. These solutions can form chiral nematic phases at rest, with tuneable photonic behavior, and exhibit a complex behavior associated with the onset of a network of director field defects under shear. Techniques, such as Nuclear Magnetic Resonance (NMR), Rheology coupled with NMR (Rheo-NMR), rheology, optical methods, Magnetic Resonance Imaging (MRI), Wide Angle X-rays Scattering (WAXS), were extensively used to enlighten the liquid crystalline characteristics of these cellulosic solutions. Cellulosic films produced by shear casting and fibers by electrospinning, from these liquid crystalline solutions, have regained wider attention due to recognition of their innovative properties associated to their biocompatibility. Electrospun membranes composed by helical and spiral shape fibers allow the achievement of large surface areas, leading to the improvement of the performance of this kind of systems. The moisture response, light modulated, wettability and the capability of orienting protein and cellulose crystals, opened a wide range of new applications to the shear casted films. Characterization by NMR, X-rays, tensile tests, AFM, and optical methods allowed detailed characterization of those soft cellulosic materials. In this work, special attention will be given to recent developments, including, among others, a moisture driven cellulosic motor and electro-optical devices.

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Distributed feedback lasing in cellulose films

Cited by 10 publications

References 17 publications

Equilibrium Liquid Crystal Phase Diagrams and Detection of Kinetic Arrest in Cellulose Nanocrystal Suspensions

Equilibrium Liquid Crystal Phase Diagrams and Detection of Kinetic Arrest in Cellulose Nanocrystal Suspensions

Dynamic and complex optical patterns from colloids of cholesteric liquid crystal droplets

From Cellulosic Based Liquid Crystalline Sheared Solutions to 1D and 2D Soft Materials

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