A review of the fabrication of photonic band gap materials based on cholesteric liquid crystals

Balamurugan, Rathinam; Liu, Jui Hsiang

doi:10.1016/j.reactfunctpolym.2016.04.012

Cited by 65 publications

(48 citation statements)

References 102 publications

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“…In particular, cholesteric helix characterized by a pitch gradient allows to achieve circular Bragg reflection over the full visible domain, which can be realized using photo-induced [25] or thermally induced [26] as experimentally demonstrated in earlier works. For recent indepth overviews we refer to review papers [27,28]. The back-home message here is that the photonic bandgap can be extended from n ⊥ p 0 < λ < n p 0 in the case of constant pitch to n ⊥ p min < λ < n p max estimated in the case of gradient-pitch cholesterics defined by a zdependent pitch p(z) = p max − (p max − p min )z/L [24].…”

Section: Position Of the Problemmentioning

confidence: 99%

Ultrabroadband gradient-pitch Bragg-Berry mirrors

2017

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The realization of geometric phase optical device operating over a broad spectral range is usually confronted with intrinsic limitations depending of the physical process at play. Here we propose to use chiral nematic liquid crystal slabs with helical ordering that varies in three dimensions. Namely, gradient-pitch cholesterics endowed with in-plane space-variant angular positioning of the supramolecular helix. By doing so, we show that the recently introduced Bragg-Berry mirrors [Opt. Lett. 41, 3972-3975 (2016)] can be endowed with ultra-broadband spectral range. Experimental demonstration is made in the case of ultra-broadband optical vortex generation in the visible domain. These results offer practical solution to the polychromatic management of the orbital angular momentum of light combining the circular Bragg reflection of chiral media with the Berry phase.

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Section: Position Of the Problemmentioning

confidence: 99%

Ultrabroadband gradient-pitch Bragg-Berry mirrors

2017

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“…The pitch P 0 depends on the molecular chirality of CLC constituent mesogens and ranges from hundreds of nanometers to many microns or more, depending on the system. An efficient method widely used to prepare CLCs is doping nematic LC mixtures with chiral additives that induce a helical structure [2,8]. For photosensitive chiral dopants (photoswitches), their helical twisting power and thus the CLC equilibrium helix pitch P 0 can be controlled by light through photoinduced changes in chiral molecular switch conformation that influence the LC's helical twisting power [11][12][13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Multiple minimum-energy paths and scenarios of unwinding transitions in chiral nematic liquid crystals

Tenishchev¹,

Kiselev²,

Ivanov³

et al. 2019

Phys. Rev. E

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We apply the minimum energy paths (MEPs) approach to study the helix unwinding transition in chiral nematic liquid crystals. A mechanism of the transition is determined by a MEP passing through a first order saddle point on the free energy surface. The energy difference between the saddle point and the initial state gives the energy barrier of the transition. Two starting approximations for the paths are used to find the MEPs representing different transition scenarios: (a) the director slippage approximation with in-plane helical structures; and (b) the anchoring breaking approximation that involves the structures with profound out-of-plane director deviations. It is shown that, at sufficiently low voltages, the unwinding transition is solely governed by the director slippage mechanism with the planar saddle point structures. When the applied voltage exceeds its critical value below the threshold of the Fréedericksz transition, the additional scenario through the anchoring breaking transitions is found to come into play. For these transitions, the saddle point structure is characterized by out-of-plane deformations localized near the bounding surface. The energy barriers for different paths of transitions are computed as a function of the voltage and the anchoring energy strengths. * tenischev.

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“…The mentioned helical structure of PCs leads to selective reflection for circularly polarized light in different optical systems (Morris et al, 2008;Choi et al, 2009;Balamurugan and Liu, 2016;Nemati et al, 2018;Ortega et al, 2018). The birefringence is typically limited to 0.3-0.4 for colourless organic compounds, and therefore the bandwidth is usually less than 100 nm in the visible spectrum (Balamurugan and Liu, 2016). However, there are also materials with different bandwidths.…”

Section: Introductionmentioning

confidence: 99%

“…For instance, Fleming et al (Fleming et al, 2002) reported measurements and simulations of a 3D tungsten crystal that has a large photonic bandgap at infrared wavelengths (from about 8 to 20 µm). An interesting review of the methods of fabrication of various photonic band gap materials based on cholesteric liquid crystals are presented in one of the recent review papers (Balamurugan and Liu, 2016). Especially, that review paper covers the methodology used recently, when the fabrication of photonic band gap materials arose.…”

Section: Introductionmentioning

confidence: 99%

Calculation of reflectance and transmittance of optical birefringent networks based on cholesteric liquid crystals

Grzelczyk

Awrejcewicz

2019

Lat. Am. j. solids struct.

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In this paper we calculated reflectance and transmittance of different optical birefringent networks sandwiched between two isotropic media. To model optical phenomena in the considered systems, we applied the 4×4 matrix method. Some interesting reflectance and transmittance spectra and polar plots for different system parameters and arbitrary incident monochromatic light were reported. The illustrated and discussed results can be useful for understanding optical phenomena in numerous birefringent media. Especially, the reflectance and transmittance spectra computed in this article can be suitable for analysis of more advanced contemporary optical systems, i.e. photonic band gap materials based on cholesteric liquid crystals.

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A review of the fabrication of photonic band gap materials based on cholesteric liquid crystals

Cited by 65 publications

References 102 publications

Ultrabroadband gradient-pitch Bragg-Berry mirrors

Ultrabroadband gradient-pitch Bragg-Berry mirrors

Multiple minimum-energy paths and scenarios of unwinding transitions in chiral nematic liquid crystals

Calculation of reflectance and transmittance of optical birefringent networks based on cholesteric liquid crystals

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