Surface-mediated alignment of nematic liquid crystals with polarized laser light

Gibbons, Wayne M.; Shannon, Paul J.; Sun, Shao‐Tang; Swetlin, Brian J.

doi:10.1038/351049a0

Cited by 1,151 publications

(585 citation statements)

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“…Orientation of liquid crystals (LCs) on various surfaces has been actively investigating in the last decades [1][2][3][4][5] due to necessity of perfectly aligned panels in LCD industry and because of serious fundamental aspects of LC various an− choring phenomena. One of advanced orientation techni− ques implies photosensitive polymer layers irradiated with polarised UV−light [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

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Exposure and temperature dependences of contact angle of liquid crystals on photoaligning surface

Gvozdovskyy¹,

Kurioz²,

Reznikov³

2009

Opto-Electronics Review

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We report on first studies of wetting of liquid crystal on photoaligning surface. We observed strong light-induced variations of a contact angle of a liquid LC 5CB on a photoaligning surface of fluoro-polyvinyl-cinnamate (PVCN-F) and we connected these variations with changes of PVCN-F polarity. We also present drastic changes of the contact angle of a nematic liquid crystal (MLC-6080) on the PVCN-F surface in a vicinity of temperature anchoring transition of liquid crystal from homeotropic orientation to planar one. We did not find any peculiarities in temperature dependence of the contact angle of isotropic liquid (glycerol) on PVCN-F and of nematic liquid crystal on pure glass in the same temperature range. It allows us to suggest that rearrangement of LC molecules and flexible fragments in the LC-polymer interface are responsible for the change of surface tensions both of LC and polymer and the observed jump of the contact angle.

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Section: Introductionmentioning

confidence: 99%

“…One of advanced orientation techni− ques implies photosensitive polymer layers irradiated with polarised UV−light [3][4][5]. Polarised UV−exposure induces anisotropy in polymer layers leading to formation of easy orientation axis on irradiated polymer surface [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Exposure and temperature dependences of contact angle of liquid crystals on photoaligning surface

Gvozdovskyy¹,

Kurioz²,

Reznikov³

2009

Opto-Electronics Review

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“…Homogenous alignment the same as the tilt alignment with a pre-tilt angle can be accomplished by mechanically rubbing a polymeric alignment layer or through photoalignment. 48 Homeotropic alignment can also be achieved using a hydrophobic film. 49 The LC reorientation in the middle of the LC cell can be controlled by the strong interaction (also called 'anchoring') between LC molecules and the substrate surface.…”

Section: Twisted Nematic (Tn) Configurationmentioning

confidence: 99%

Fundamentals of phase-only liquid crystal on silicon (LCOS) devices

2014

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This paper describes the fundamentals of phase-only liquid crystal on silicon (LCOS) technology, which have not been previously discussed in detail. This technology is widely utilized in high efficiency applications for real-time holography and diffractive optics. The paper begins with a brief introduction on the developmental trajectory of phase-only LCOS technology, followed by the correct selection of liquid crystal (LC) materials and corresponding electro-optic effects in such devices. Attention is focused on the essential requirements of the physical aspects of the LC layer as well as the indispensable parameters for the response time of the device. Furthermore, the basic functionalities embedded in the complementary metal oxide semiconductor (CMOS) silicon backplane for phase-only LCOS devices are illustrated, including two typical addressing schemes. Finally, the application of phase-only LCOS devices in real-time holography will be introduced in association with the use of cutting-edge computer-generated holograms. The architecture of LCOS devices is similar to conventional LC devices except that a silicon backplane constitutes one of the substrates (Figure 1). The silicon CMOS backplane consists of the electronic circuitry that is buried underneath pixel arrays to provide a high 'fill factor'. The pixels are aluminum mirrors deposited on the surface of the silicon backplane. The incident light is transmitted through the LC layer with almost zero absorption. The integration of high-performance driving circuitry allows the applied voltage to be changed on each pixel, thereby controlling the phase retardation of the incident wavefront across the device. Currently, there are two types of light modulation using LCOS devices, amplitude modulation and phase modulation. In the former case, the amplitude of the light signal is modulated 6,7 by varying the linear polarzation direction of the incident light passing through a linear polarizer, the same principle used in a standard LC television. In the latter case, the phase delay is accomplished by electrically adjusting the optical refractive index along the light path, which is possible because of the non-zero birefringence of the LC materials in use but should be carefully characterized. [8][9][10][11][12][13] In a phase-only LCOS SLM modulator, no light absorption by polarizers or other light-absorbing components will occur, such that the maximum light efficiency can be expected.Currently, most of the conventional LC devices are not able to efficiently modulate the phase of an incident wavefront. For instance, the LC device structure using thin film transistors is not suitable for phase modulation because an appropriate electro-optic effect has not been used (see the section on 'Twisted nematic (TN) configuration' and the section on 'VAN configuration' for details). Moreover, the pixels of this type of device are too large to provide acceptably large diffraction angles. In addition, the pixel circuitry and connection tracks are in the light path such that the ...

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“…Since these modulations are photoinitiated, it is straightforward to create patterns (Shannon et al, 1994). These LC photoswitching effects are obviously attractive in many applications, such as for display devices, optical memories (Gibbons et al, 1991), electro-optics (Luk and Abbott, 2003), and modulating the polarization of ferroelectric liquid crystals (Fischer et al, 1997;Ikeda et al, 1993).…”

Section: Classes Of Azobenzene Systemsmentioning

confidence: 99%

“…The photoisomerization of azobenzene leads to modification of the phase and alignment (director) in LC systems (Shibaev et al, 2003;Ichimura, 2000). The director of a liquid crystal phase can be modified by orienting chromophores doped into the phase (Sun et al, 1992;Anderle et al, 1991) by using an azobenzene-modified ''command surface'' (Chen and Brady, 1993;Ichimura et al, 1993;Gibbons et al, 1991), using azo copolymers (Wiesner et al, 1991), and, of course, in pure azobenzene LC phases (Hvilsted et al, 1995;Stumpe et al, 1991). One can force the LC phase to adopt an in-plane order (director parallel to surface), homeotropic alignment (director perpendicular to surface), tilted or even biaxial orientation (Yaroschuk et al, 2001).…”

Section: Classes Of Azobenzene Systemsmentioning

confidence: 99%