Fast switchable grating based on orthogonal photo alignments of ferroelectric liquid crystals

Srivastava, Abhishek Kumar; Hu, Wei; Chigrinov, Vladimir G.; Kiselev, Alexei D.; Lu, Yanqing

doi:10.1063/1.4737642

Cited by 91 publications

(81 citation statements)

References 19 publications

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“…In this paper, the used FLC materials is working in a electro-optical mode called electrically suppressed helix (ESH) mode, which is characterized by the good alignment quality and faster response time at low driving voltages [32,33]. The working principle of the ESH FLC can be illustrated by Figure 1.…”

Section: Resultsmentioning

confidence: 99%

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Ferroelectric Liquid Crystal Dammann Grating by Patterned Photoalignment

et al. 2017

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Abstract:In this article, a ferroelectric liquid crystal (FLC) dammann grating (DG) is demonstrated based on the patterned photoalignment technology. By applying low electric field (10 V) on the FLC DG, the grating can switch between a diffractive state with 7 × 7 optical spots array and a non-diffractive state, depending on the polarity of electric field. The FLC DG shows very fast switching speed with switching on time and off time to be only 81 µs and 59 µs respectively. Comparing with other fast LC DGs such as the ones based on blue phase LC or dual-frequency LC, the switching speed of the proposed FLC DG is about one order faster, which provides great potential and perspective for the FLC DG to be applied in a broad range of optical applications such as optical communication and beam shaping.

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Section: Resultsmentioning

confidence: 99%

“…FLC is considered to be a good candidate for modern display and photonics applications [32,33], which shows nearly the fastest switching speed among all the LC materials. In this paper, a faster switching FLC DG based on patterned photoalignment is demonstrated.…”

Section: Introductionmentioning

confidence: 99%

Ferroelectric Liquid Crystal Dammann Grating by Patterned Photoalignment

et al. 2017

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“…20 Furthermore, an approach has been proposed to realize FLC diffraction element, which includes double-sided alignment fabrication procedure. 21 This method incorporates the two-step alignment procedure simultaneously on both top and bottom substrates, which reduces the cell assembling complexity for one to one domain alignment matching. However, because of the beam size expansion and LC disclination, the exact pattern cannot be transferred to alignment layer precisely and, therefore, this method does not work precisely for the small grating pitches.…”

Section: Introductionmentioning

confidence: 99%

“…However, because of the beam size expansion and LC disclination, the exact pattern cannot be transferred to alignment layer precisely and, therefore, this method does not work precisely for the small grating pitches. 21 To overcome these limitations, a single-side alignment method can be used. 22 It has been proved that these kinds of asymmetric boundary conditions alignment procedure are a better option to avoid a competition between aligning forces and FLC helix which can give better alignment quality to FLC grating cells.…”

Section: Introductionmentioning

confidence: 99%

Fast switchable ferroelectric liquid crystal gratings with two electro-optical modes

Ma¹,

Wang

Srivastava³

et al. 2016

AIP Advances

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In this article, we reveal a theoretical and experimental illustration of the Ferroelectric liquid crystal (FLC) grating fabricated by mean of patterned alignment based on photo-alignment. The complexity related to the mismatching of the predefined alignment domains on the top and bottom substrate has been avoided by incorporating only one side photo aligned substrate while the other substrate does not have any alignment layer. Depending on the easy axis in the said alignment domains and the azimuth plane of the impinging polarized light, the diffracting element can be tuned in two modes i.e. DIFF/OFF switchable and DIFF/TRANS switchable modes, which can be applied to different applications. The diffraction profile has been illustrated theoretically that fits well with the experimental finding and thus the proposed diffraction elements with fast response time and high diffraction efficiency could find application in many modern devices.

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“…The easy axis and value of A φ can only be changed by another exposure by the same light source with a different E-vector. Moreover, A φ also depends on the SD1 layer thickness; for such applications it has already been optimized to 10 nm [22][23][24].…”

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confidence: 99%

Optically tunable and rewritable diffraction grating with photoaligned liquid crystals

et al. 2013

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An optically tunable and rewritable liquid crystal (LC) diffraction grating cell has been revealed that consists of an optically active and an optically passive alignment layer. The grating profile is created by confining the LC director distribution in alternate planar and twisted alignment domains by means of photoalignment of the LCs. The proposed grating is optically tunable for diffractive and nondiffractive states with a small response time that depends on the exposure energy and LC parameters. In addition, the grating can be erased and rewritten for different diffracting characteristics. Another approach is to utilize the natural diffracting ability of the chiral LCs [12]. Such gratings are electrically tunable but cannot be tuned optically [12,13]. In recent years some reports dealing with optical tunability of dye-doped organic materials have been written [14]. Confined complex structures such as polymer-LC-polymer-slide (PLCPS) gratings containing azo compounds show optical switching times of 0.5 s at the irradiance of 245 mW∕cm 2 and diffraction efficiencies (DEs) up to 85% [15]. In another report, a 90% DE and switching time of 0.2 s (at the irradiance of 54 mW∕ cm 2 ) were reported for PLCPS with photosensitive LC [16]. Most of these reports include dye-doped LC for a photopolymerizable mixture for recording the grating. However, azo dyes, because of their chemical instability, are not stable in the LC mixture, and therefore the efficiency of these devices is highly limited and they manifest a rather complex fabrication procedure [17]. Another approach, based on a polydimethylsiloxane periodic microstructure on a glass substrate, separated by a thin LC film, with a DE of 35% and switching time of 145 s at the irradiance of 600 mW∕cm 2 , has been reported [18]. Other than LC, a metamaterial [19] fabricated by encapsulating photochromic solution in nano-holes of polycarbonate has also been proposed for fabricating optically tunable gratings [4]. The interference pattern by the green laser was used to write the grating profile, whereas it can be erases by UV irradiation [20,21]. However, the technology is restricted by the large switching time of ∼30 s (at an irradiance of 300 mW∕cm 2 ). Recently, we have disclosed a relatively easier and more reliable method to fabricate electrically tunable gratings, by defining the LC director in alternate alignment domains of alternate planar (PA) and twisted (TN) alignments by means of photoalignment [22]. Moreover, among all of these strategies, patterned photoalignment has been demonstrated to be efficient [11][12][13].In this article, we present an optically tunable LC grating based on PA and TN alignment domains. The blue light (λ 450 nm) can be used to tune the diffractive and nondiffractive states. Such gratings can also be erased and rewritten for different grating vectors. Thus, they could find several applications.The optically tunable and rewritable (OTRW) LC cell consists of two substrates with different aligning materials, one of which is optically pas...

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Fast switchable grating based on orthogonal photo alignments of ferroelectric liquid crystals

Cited by 91 publications

References 19 publications

Ferroelectric Liquid Crystal Dammann Grating by Patterned Photoalignment

Ferroelectric Liquid Crystal Dammann Grating by Patterned Photoalignment

Fast switchable ferroelectric liquid crystal gratings with two electro-optical modes

Optically tunable and rewritable diffraction grating with photoaligned liquid crystals

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