Polarization-independent phase modulation using a polymer-dispersed liquid crystal

Ren, Hongwen; Lin, Yi‐Hsin; Fan, Yun‐Hsing; Wu, Shin Tson

doi:10.1063/1.1899749

Cited by 119 publications

(83 citation statements)

References 17 publications

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“…Two major technical challenges have severely limited their practical applications and commercialization: polarization dependency and slow response time (several seconds or hundreds of milliseconds). The former can be solved by using residual phase modulations [26,27], and optical isotropic materials, such as blue phase LC [28][29][30][31][32][33][34], double-layered structure [35][36][37], or axially symmetric photoalignment [38]. Due to the intrinsic speed of NLCs, the response time of a LC microlens is usually in the order of 100 ms, which is obviously not fast enough for image processing, optical communication, etc.…”

Section: Introductionmentioning

confidence: 99%

Fast-Response Liquid Crystal Microlens

Liu

et al. 2014

Micromachines

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Electrically tunable liquid crystal microlenses have attracted strong research attention due to their advantages of tunable focusing, voltage actuation, low power consumption, simple fabrication, compact structure, and good stability. They are expected to be essential optical devices with widespread applications. However, the slow response time of nematic liquid crystal (LC) microlenses has been a significant technical barrier to practical applications and commercialization. LC/polymer composites, consisting of LC and monomer, are an important extension of pure LC systems, which offer more flexibility and much richer functionality than LC alone. Due to the anchoring effect of a polymer network, microlenses, based on LC/polymer composites, have relatively fast response time in comparison with pure nematic LC microlenses. In addition, polymer-stabilized blue phase liquid crystal (PS-BPLC) based on Kerr effect is emerging as a promising candidate for new photonics application. The major attractions of PS-BPLC are submillisecond response time and no need for surface alignment layer. In this paper, we review two types of fast-response microlenses based on LC/polymer composites: polymer dispersed/stabilized nematic LC and polymer-stabilized blue phase LC. Their basic operating principles are introduced and recent progress is reviewed by examples from recent literature. Finally, the major challenges and future perspectives are discussed. OPEN ACCESSMicromachines 2014, 5 301

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Section: Introductionmentioning

confidence: 99%

Fast-Response Liquid Crystal Microlens

Liu

et al. 2014

Micromachines

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“…This can be solved by using many other structures of LC lens operated with a driving voltage below 10 V rms [10,21]. Moreover, the optical efficiency can be enhanced by using polarization independent LC phase modulator, including double layered type, residual phase type or mixed type [17,20,[22][23][24][25][26][27][28][29][30].…”

Section: Experiments and Discussionmentioning

confidence: 99%

An Electrically Tunable Liquid Crystal Lens for Fiber Coupling and Variable Optical Attenuation

Lin¹

2014

J Elec Electron Syst

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In this paper, an electrically tunable LC lens for fiber coupling and variable optical attenuation is proposed and demonstrated. The LC lens electrically changes the lens power in order to adjust the beam size incident on the fiber. When the beam size is closed to the core size of the fiber, the LC lens is operated as a lens coupler. When the beam size increases by reducing the lens power, the LC lens is operated as a VOA. After introducing the operating principles, we use a LC lens to experimentally demonstrate the design concept and the results show that the maximum coupling efficiency can be 0.75 and the maximum attenuation can be as large as18 dB. The concept proposed in this paper is not only for LC lenses, but also for other optical components with electrically tunable focusing properties. The study provides a new way to design an optical device for fiber coupling and variable optical attenuation based on electrically tunable focusing optical components. Figure 1a and 1b depict a typical structure of the LC lens with positive and negative lens operations. We use the hole-patterned LC lens to demonstrate the concept [11,12]. In fact, the concept we proposed here can be applied to other structures of LC lenses. The components of the LC lens included three Indium Tin Oxide (ITO) glass substrates, two Polyvinyl Alcohol (PVA) layers for LC alignment, an insulating layer (Norland product Inc. NOA81), and a 50 μm nematic LC layer (Merck MLC-2070, Δn=0.2609). In order to generate an inhomogeneous electric field, the ITO layer in the middle of the glass substrate was etched with a hole and connected to an applied Alternating Current (AC) voltage of V 1 . PVA layers were coated on the glass substrates and mechanically rubbed in one direction to align the LC molecules. As a result, the LC molecules are aligned parallel to the glass substrate (x-direction in Figure 1) as V 1 =V 2 =0V rms and provide zero lens power (i.e. inverse of the focal length) for x-linearly polarized light. Mechanism and Operating Principles AbstractAn electrically tunable Liquid Crystal (LC) lens for both of fiber coupling and variable optical attenuation is demonstrated. The LC lens modulates the beam waist coupling to the fiber by electrically changing the lens power. When the modulated beam waist is close to the core size of the fiber, the LC lens is operated as a lens coupler. When the beam waist increases by reducing the lens power, the LC lens is operated as a Variable Optical Attenuator (VOA) as a result of the corresponding coupling coefficient variation of the transformed beam into a multimode fiber. The study provides a way to design an optical device for fiber coupling and variable optical attenuation based on electrically tunable focusing optical component.

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“…To remove the requirement of a polarizer, a polarization independent LC phase modulation is required. Many polarization independent LC phase modulations are demonstrated and proposed [35][36][37][38][39][40][41][42][43]. Table 15.1 lists the performances of polarization-independent phase modulations in the literatures, such as phase shift, driving voltage and response time.…”

Section: Ophthalmic Lenses Using Nematic Liquid Crystalsmentioning

confidence: 99%

Liquid Crystals for Bio-medical Applications

Lin

2014

Topics in Applied Physics

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Thermotropic nematic LCs can modulate light in phases, amplitudes, and polarizations [1]. Many photonic applications based LCs have developed, such as displays, electro-optical switches, lenses, optical vortex generators, variable optical attenuations, solar cells and so on. Thermotropic nematic LCs have great potential in bio-medical applications. In this session, we mainly introduce two the bio-medical applications based on thermotropic nematic LCs: biosensors and ophthalmic lenses. In biosensors, the key is interfacial interactions between biosamples and LC molecules. We will introduce a LC and polymer complex system, the LC and polymer composite film (LCPCF), whose surface free energy is electrically switchable. LCPCF can help to test the sperm quality and high-density-lipoprotein (HDL). In ophthalmic applications, we will introduce the challenges and requirements for design of ophthalmic lenses. A polarizer-free LC lens with large aperture size is also introduced. Biosensors Using Nematic Liquid CrystalsIn general, interfacial interactions between LCs and bio-samples (or sensing targets) are the key to design a biosensor using nematic LCs [2][3][4][5][6][7]. Such an interfacial interaction often causes the re-orientations of LC molecules at the interface. As a result, optical properties of LC change and the change of the orientation of LC can be read out by observing under a polarizing microscopy. LC can optically amplify the biological binding events and help us to study the biology. The main approach is to immobilize thermotropic nematic LC onto a solid surface as a sensing interface for bio-samples. 5CB is a commonly used a LC material for biosensing. In the literatures, 5CB has been proved for sensing many bio-samples,

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Polarization-independent phase modulation using a polymer-dispersed liquid crystal

Cited by 119 publications

References 17 publications

Fast-Response Liquid Crystal Microlens

Fast-Response Liquid Crystal Microlens

An Electrically Tunable Liquid Crystal Lens for Fiber Coupling and Variable Optical Attenuation

Liquid Crystals for Bio-medical Applications

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