All-optical responsive azo-doped liquid crystal laser protection filter

Jull, Ethan I. L.; Gleeson, Helen F.

doi:10.1364/oe.26.034179

Cited by 7 publications

(3 citation statements)

References 22 publications

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“…Dyes are usually organic compounds of natural origin or synthetic, having affinity to the substrate onto which they are applied [1][2][3]. Among dyes, the azoic compounds [2] are a well-known class of substances, which are frequently employed in specific applications for their physical and biological properties [4][5][6][7][8][9]: as liquid crystals [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], industrial [29][30][31][32][33][34][35][36][37][38][39] and food colouring agents [40][41][42][43][44][45], pharmaceuticals [35,36,[46]…”

Section: Introductionmentioning

confidence: 99%

Physical, Thermal and Biological Properties of Yellow Dyes with Two Azodiphenylether Groups of Anthracene

et al. 2020

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Two yellow bis-azo dyes containing anthracene and two azodiphenylether groups (BPA and BTA) were prepared, and an extensive investigation of their physical, thermal and biological properties was carried out. The chemical structure was confirmed by the FTIR spectra, while from the UV–Vis spectra, the quantum efficiency of the laser fluorescence at the 476.5 nm was determined to be 0.33 (BPA) and 0.50 (BTA). The possible transitions between the energy levels of the electrons of the chemical elements were established, identifying the energies and the electronic configurations of the levels of transition. Both crystals are anisotropic, the optical phenomenon of double refraction of polarized light (birefringence) taking place. Images of maximum illumination and extinction were recorded when the crystals of the bis-azo compounds rotated by 90° each, which confirms their birefringence. A morphologic study of the thin films deposited onto glass surfaces was performed, proving the good adhesion of both dyes. By thermal analysis and calorimetry, the melting temperatures were determined (~224–225 °C for both of them), as well as their decomposition pathways and thermal effects (enthalpy variations during undergoing processes); thus, good thermal stability was exhibited. The interaction of the two compounds with collagen in the suede was studied, as well as their antioxidant activity, advocating for good chemical stability and potential to be safely used as coloring agents in the food industry.

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Section: Introductionmentioning

confidence: 99%

Physical, Thermal and Biological Properties of Yellow Dyes with Two Azodiphenylether Groups of Anthracene

et al. 2020

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“…The azobenzene-based mesogen used in this device was 4-2-butyl-4'-2-alkoxyazobenzene (BAAB2), described in further detail by S. V. Serak et al 12 and used in another embodiment of passive laser protection described by us recently 4 . BAAB2 was doped into the LC host 4-pentyl-4'-cyanobiphenyl (5CB) with varying concentration between 5 and 10 %(w/w) (mix-5 to mix-10 respectively).…”

Section: Methodsmentioning

confidence: 99%

“…This later threat is especially relevant when attacks against pilots are considered. The development of novel liquid crystal (LC) optical protection devices which combat this problem are currently underway [3][4][5][6] , with the switchable optical properties of LCs providing an excellent basis for electrically switchable protective devices. Development of a passive switchable filter, which responds directly to the laser threat, is a bigger challenge that can be realized when incorporation of light sensitive azobenzene based mesogens into the LC system is considered.…”

Section: Introductionmentioning

confidence: 99%

Novel devices with photosensitive elements

Jull

Gleeson

2019

Emerging Liquid Crystal Technologies XIV

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Liquid Crystal (LC) devices with photosensitive elements have incredible scope for creating unique photo-induced optical devices.The use of azobenzene based materials, which undergo a trans-cis isomerisation when irradiated with light of a specific wavelength, is firmly established in LC research. The trans conformation is an elongated rod-like shape, similar to LC mesogens, whilst the cis conformation is closer to a spherical (bent) shape, disrupting to the LC order. When these materials are doped into LC materials they are able to produce light induced responses, and therefore their application to photo-switchable optics and devices is undeniable. In this research paper the light induced order modification, rather than light induced reorientation, is utilized to produce an all-optical switchable laser protection device.Upon irradiation of an azo-doped LC system with a continuous, low power (0.5 mW), laser threat ( =405 nm) the transcis photoisomerisation process is triggered. This results in the trans-cis conformal shape change, lowering of the LC order, and causing the system to switch from the LC nematic phase (transmitting between crossed polarisers) to the isotropic liquid phase (blocking/dark between crossed polarisers). The optical properties of the azo-doped LC materials have been characterized and the response time dependence on azo-dopant concentration, system temperature, and laser threat intensity is thoroughly investigated.

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