&lt;title&gt;Ultrasonic liquid crystal-based underwater acoustic imaging&lt;/title&gt;

Gerdt, David W.; Baruch, Martin; Adkins, Charles M.

doi:10.1117/12.343873

Cited by 8 publications

(1 citation statement)

References 1 publication

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“…23 LC realignment based on acoustic waves has already found valuable applications within the areas of imaging [24][25][26] and medical diagnostics. [27][28][29] Ozaki et al 30,31 used acoustic streaming to change the alignment of cholesteric LC molecules and demonstrate a lasing effect.…”

Section: Introductionmentioning

confidence: 99%

Holographically Formed, Acoustically Switchable Gratings Based on Polymer-Dispersed Liquid Crystals

Liu

Ding

et al. 2013

SLAS Technology

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Section: Introductionmentioning

confidence: 99%

Holographically Formed, Acoustically Switchable Gratings Based on Polymer-Dispersed Liquid Crystals

Liu

Ding

et al. 2013

SLAS Technology

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Surface Acoustic Wave Driven Light Shutters Using Polymer‐Dispersed Liquid Crystals

et al. 2011

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In recent years, polymer-dispersed liquid crystals (PDLCs) [ 1 ] have been used in many applications including smart windows, [ 2 ] displays, [ 3 ] microlenses, [ 4 , 5 ] lasers, [ 6 , 7 ] and data storage, [ 8 ] due to their excellent electro-optical properties. PDLC fi lms can be prepared between two conductive, transparent substrates using methods such as encapsulation, thermally induced phase separation, solvent-induced phase separation, and polymerizationinduced phase separation. [ 9 ] Within a PDLC fi lm, liquid crystals (LCs) are generally trapped in a transparent polymer medium, thus forming micrometer-scale LC droplets. The random dispersion of LC droplets in the polymer matrix causes a strong scattering of light due to the signifi cant refractive index mismatch between the two materials; therefore, a PDLC fi lm is naturally opaque. Based on laser interference holography, various periodic structures such as gratings [10][11][12] and photonic crystals, [ 13 , 14 ] can be also introduced inside the fi lm, coined as holographic PDLCs (HPDLCs). [ 15 ] The application of an electric fi eld can re-orientate the LC molecules inside a droplet, thus modulating the refractive index difference between the polymer matrix and the LC. A complete refractive index match between the two materials can be achieved by tuning the LCs to a specifi c orientation. In such a way, the PDLC fi lm can be switched from opaque to transparent. The switching properties of PDLCs are infl uenced by many variables including the size and shape of the LC droplets, [ 16 , 17 ] and molecular interactions between the LCs and polymer matrix. [ 18 , 19 ] The dynamic switching of PDLCs has been extensively studied based on electrically-and optically-driven methods; [ 20 , 21 ] however, both methods have their respective limitations. For instance, electrically-driven PDLCs require a high driving electric fi eld ( > 1 V/ μ m), [ 18 ] while optically-driven methods have shown poor optical contrast (only 1 − 3). [ 20 ] To overcome these limitations, researchers continue to search for driving schemes that can achieve low power consumption, high throughput, and excellent optical properties.Besides electrical and optical driving, LC re-alignment has also been demonstrated based on the acousto-optic effect, [22][23][24] where acoustic waves change the optical axis of a LC system, thus changing the transmitted light intensity. [ 23 ] Various mechanisms have been proposed to explain the LC molecules' re-orientation upon application of acoustic waves, such as acoustic streaming [ 25 , 26 ] and minimum entropy generation. [ 27 ] Acoustic streaming describes a steady fl ow in a fl uid generated by propagating acoustic waves. [ 28 ] Due to the absorption, viscosity, and thermal conduction of the fl uid, the acoustic wave attenuates while propagating. The attenuated acoustic wave exerts a net force on the fl uid through momentum conservation and causes the steady fl ow. Ozaki et al . used acoustic streaming to change the alignment of cholesteric LC mol...

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Acousto-optic response of nematic liquid crystals

Greanya

Spector

Selinger

et al. 2003

Journal of Applied Physics

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The dependence of the acousto-optic response of two nematic liquid crystals on several possible future device parameters is investigated. Several paths for possible optimization are identified. A large enhancement of the acousto-optic response is obtained through optimization of the incident angle of the acoustic wave. The power required for a given cell to reach the maximum optical intensity is also reduced by adjusting the optical angle. This reduction comes at the expense of higher zero-field intensity, and therefore lowers the overall contrast. Finally, the acousto-optic response shows a significant dependence on liquid crystal layer thickness, scaling with the theoretically predicted fifth power of the cell thickness.

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<title>Ultrasonic liquid crystal-based underwater acoustic imaging</title>

Cited by 8 publications

References 1 publication

Holographically Formed, Acoustically Switchable Gratings Based on Polymer-Dispersed Liquid Crystals

Holographically Formed, Acoustically Switchable Gratings Based on Polymer-Dispersed Liquid Crystals

Surface Acoustic Wave Driven Light Shutters Using Polymer‐Dispersed Liquid Crystals

Acousto-optic response of nematic liquid crystals

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