Single walled carbon nano-tube, ferroelectric liquid crystal composites: Excellent diffractive tool

Srivastava, Abhishek Kumar; Pozhidaev, E. P.; Chigrinov, Vladimir G.; Manohar, Rajiv

doi:10.1063/1.3661170

Cited by 48 publications

(32 citation statements)

References 20 publications

(22 reference statements)

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“…For liquid crystal polarization grating [5,6] which can achieve binary LC grating, also show slow switching speed. Therefore, Ferroelectric liquid crystal (FLC) with ultra-fast response time can be a good alternative [7]. In this article, we propose a method to fabricate the FLC grating which can modulate the diffraction profile with fast speed and at a cost of very small power consumption.…”

Section: Introductionmentioning

confidence: 99%

P‐105: Fast Switchable Grating Based on Ferroelectric Liquid Crystal

Guo

Srivastava

et al. 2012

Symp Digest of Tech Papers

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Section: Introductionmentioning

confidence: 99%

P‐105: Fast Switchable Grating Based on Ferroelectric Liquid Crystal

Guo

Srivastava

et al. 2012

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“…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].…”

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“…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].…”

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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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“…The FLC can be a potential candidate, because of the fast response time and less driving voltages, but due to some fundamental problems (viz., geometry defects, shock problem, poor contrast, etc), it is very hard to develop a real device. 5,13 On the other hand to increase the speed of the nematic LC devices, several methods, viz., fringe field effect, guest host effect, etc, have been proposed so far but the response time is typically limited to 1 ms. 17,18 However, recently, Morris et al have disclosed a fast switchable grating based on polymer stabilized short pitch chiral LC. 19 The characteristic switching time for this grating is 600 ls, whereas the required electric field is around 20 V/lm, which is relatively high.…”

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“…Switchable grating is one of these elements which has been studied broadly. [1][2][3][4][5] Recently, several types of switchable gratings have been proposed. To construct a grating profile, periodical refractive index change of LC is necessary which can be generated by three basic approaches.…”

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Switchable liquid crystal grating with sub millisecond response

Fan

Srivastava

Chigrinov

et al. 2012

Applied Physics Letters

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In present article, we disclose a fast switchable grating based on nematic liquid crystals. A fine striped electrode has been exploited to generate the grating profile and a driving scheme to drive the grating cell has also been proposed, which enable us to drive the cell up to very high frequency (∼2 kHz) with evident saturated optical states. The response time for the first order diffracted beam, at the electric field of 10 V/μm, is less than 100 μs and optical contrast is higher than 400:1. Thus, the proposed LC grating could find application in several advance electro-optical devices.

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Single walled carbon nano-tube, ferroelectric liquid crystal composites: Excellent diffractive tool

Cited by 48 publications

References 20 publications

P‐105: Fast Switchable Grating Based on Ferroelectric Liquid Crystal

P‐105: Fast Switchable Grating Based on Ferroelectric Liquid Crystal

Optically tunable and rewritable diffraction grating with photoaligned liquid crystals

Switchable liquid crystal grating with sub millisecond response

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