Photosensitive and all-optically fast-controllable photonic bandgap device and laser in a dye-doped blue phase with a low-concentration azobenzene liquid crystal.

This work demonstrates the feasibility of a novel photosensitive and all-optically fast-controllable photonic bandgap (PBG) device based on a dye-doped blue phase (DDBP), embedded with a low-concentration azobenzene liquid crystal (azo-LC). PBG of the DDBP can be reversibly fast-tuned off and on with the successive illumination of a weak UV and green beams. UV irradiation can transform the trans azo-LCs into bend cis isomers, which can easily disturb LCs at the boundary between the double twisting cylinders (DTCs) and the disclinations, and, then, quickly destabilize BPI to become a BPIII-like texture with randomly-oriented DTCs. Doing so may quickly destroy the BP PBG structure. However, with the successive illumination of a green beam, the BPI PBG device can be fast-turned on, owing to the fast disappearance of the disturbance of the azo-LCs on the boundary LCs via the green-beam-induced cis → trans back isomerization. The response time and irradiated energy density for turning off (on) the BP PBG device under the UV (green) beam irradiation are only 120 ms (120 ms) and 0.764 mJ/cm(2) (2.12 mJ/cm(2)), respectively, which are a thousand-fold reduction in photoswitching a traditional cholesteric LC (CLC) PBG device based on similar experimental conditions (i.e., materials used, azo-LC concentration (1 wt%), spectral position of PBG peak, sample thickness, and temperature difference for a working temperature lower than the clearing one). The BP PBG device can significantly contribute to efforts to develop a photosensitive and all-optically fast-controlling LC laser.

[Fluorescent labeling of latent fingerprints with metallic ions modified ZnS/PAMAM nano-composites].

Abstract Effects of metallic ions, such as Zn2+ , Mn , Cd2+, Na+, K+, Ag, CuZ+ and PbZ, on the photoluminescence properties of ZnS(ZINC sulfide) QDs (quantum dots)/poly (amido amine) (PAMAM) dendrimer nanocomposites(NCs) with blue emission under the irradiation of UV light were studied. The results show that the effects of different metallic ions on the photoluminescence properties of the prepared ZnS QDs were different. Zn+ , Mn2+ and Cd2+ ions enhance the PL(photoluminescence) intensity; Na+ and K+ ions don't change the PL intensity obviously while Ag+, Cu2+ and Pb2+ quench it. Compared with ZnS/PAMAM NCs, fingerprints treated with ZnxCd1-x) S/PAMAM NCs emitted brighter blue light, the contrast between abstracts and fingerprints was more obvious, which shows good reference

Polymer-Based Device Fabrication and Applications Using Direct Laser Writing Technology.

Polymer materials exhibit unique properties in the fabrication of optical waveguide devices, electromagnetic devices, and bio-devices. Direct laser writing (DLW) technology is widely used for micro-structure fabrication due to its high processing precision, low cost, and no need for mask exposure. This paper reviews the latest research progresses of polymer-based micro/nano-devices fabricated using the DLW technique as well as their applications. In order to realize various device structures and functions, different manufacture parameters of DLW systems are adopted, which are also investigated in this work. The flexible use of the DLW process in various polymer-based microstructures, including optical, electronic, magnetic, and biomedical devices are reviewed together with their applications. In addition, polymer materials which are developed with unique properties for the use of DLW technology are also discussed.