Polarization independent liquid crystal gratings based on orthogonal photoalignments

Hu, Wei; Srivastava, Abhishek Kumar; Lin, Xiao-wen; Liang, Xiao; Wu, Zijian; Sun, Jun; Zhu, Ge; Chigrinov, Vladimir G.; Lu, Yanqing

doi:10.1063/1.3694921

Cited by 78 publications

(55 citation statements)

References 20 publications

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“…Since for both the two polarizations, the phase difference all follows the well-designed domain structure, the diffractive performance of the DG can be considered as polarization-independent for both states. The LC device structure with orthogonal oriented LC molecule and π phase difference between neighbored domains is commonly used for realizing lots of other optical elements such as Fresnel plate [34] and grating [35]. In our design, the switchability of the device is critical important.…”

Section: Resultsmentioning

confidence: 99%

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%

Ferroelectric Liquid Crystal Dammann Grating by Patterned Photoalignment

et al. 2017

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“…Therefore, the proposed OTRW grating has a high resolution and fast switching speed (∼100 ms) at considerably less exposure energy than the existing technologies. Thus, it could find application in a wide range of photonic and adaptive optical elements and other optical devices [10][11][12][13][14]. This work is supported by HKUST grants CERG 612409, CERG 612310, and RGC 614410.…”

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confidence: 99%

“…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].…”

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confidence: 99%

“…The most common approach deals with arrays of parallel electrodes for generating a longitudinal [5,6] or lateral [7,8] periodic electrical field distribution and locally controlling the directors of the LCs and thus the diffraction. The second strategy is to directly pattern the LC alignment layers either by microrubbing [9,10] or by patterned photoalignment [11] and guiding the LC director in different alignment domains. Another approach is to utilize the natural diffracting ability of the chiral LCs [12].…”

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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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“…Various types of LC gratings [12][13][14] have already been studied but they suffer through slow switching speed, high power consumption, and low diffraction efficiency [1, [3][4]. For liquid crystal polarization grating [5,6] which can achieve binary LC grating, also show slow switching speed.…”

Section: Introductionmentioning

confidence: 99%