TY  - JOUR
A1  - Ryabchun, Alexander
A1  - Sakhno, Oksana
A1  - Stumpe, Joachim
A1  - Bobrovsky, Alexey
T1  - Full-Polymer Cholesteric Composites for Transmission and Reflection Holographic Gratings
JF  - Advanced optical materials
N2  - A new type of self-organized materials based on cholesteric networks filled with photoactive side-chain copolymer is being developed. Supramolecular helical structure of cholesteric polymer network resulting in the selective reflection is used as a photonic scaffold. Photochromic azobenzene-containing nematic copolymer is embedded in cholesteric scaffold and utilized as a photoactive media for optical pattering. 1D and 2D transmission diffraction gratings are successfully recorded in composite films by holographic technique. For the first time the possibility to create selective reflection gratings in cholesteric material mimicking the natural optical properties of cholesteric mesophase is demonstrated. That enables the coexistence of two selective gratings, where one has an intrinsic cholesteric periodic helical structure and the other is a holographic grating generated in photochromic polymer. The full-polymer composites provide high light-induced optical anisotropy due to effective photo-orientation of side-chain fragments of the azobenzene-containing liquid crystalline polymer, and prevent the degradation of the helical superstructure maintaining all optical properties of cholesteric mesophase. The proposed class of optical materials could be easily applied to a broad range of polymeric materials with specific functionality. The versatility of the adjustment and material preprogramming combined with high optical performance makes these materials a highly promising candidate for modern optical and photonic applications.
KW  - azobenzene
KW  - cholesteric scaffolds
KW  - holography
KW  - LC polymer
KW  - polarization diffraction grating
KW  - reflection grating
Y1  - 2017
U6  - https://doi.org/10.1002/adom.201700314
SN  - 2195-1071
VL  - 5
SP  - 376
EP  - 379
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Heydari, Esmaeil
A1  - Pastoriza-Santos, Isabel
A1  - Liz-Marzan, Luis M.
A1  - Stumpe, Joachim
T1  - Nanoplasmonically-engineered random lasing in organic semiconductor thin films
JF  - Nanoscale horizons
N2  - We demonstrate plasmonically nano-engineered coherent random lasing and stimulated emission enhancement in a hybrid gainmedium of organic semiconductors doped with core-shell plasmonic nanoparticles. The gain medium is composed of a 300 +/- 2 nm thin waveguide of an organic semiconductor, doped with 53 nm gold nanoparticle cores, isolated within silica shells. Upon loading the nanoparticles, the threshold of amplified spontaneous emission is reduced from 1.75 mu J cm(-2) x 10(2) for an undoped gain medium, to 0.35 mu J cm(-2) x 10(2) for a highly concentrated gain medium, and lasing spikes narrower than 0.1 nm are obtained. Most importantly, selection of silica shells with thicknesses of 10, 17 and 21 nm enables engineering of the plasmon-exciton energy coupling and consequently tuning of the laser slope efficiency. With this approach, the slope efficiency is increased by two times by decreasing the silica shell from 21 nm down to 10 nm, due to the enhancement of the localized electric field.
Y1  - 2017
U6  - https://doi.org/10.1039/c7nh00054e
SN  - 2055-6756
SN  - 2055-6764
VL  - 2
SP  - 261
EP  - 266
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  -