An optically active diffractive device for a high‐efficiency light valve

Bos, Philip J.; Chen, J.; Doane, J. William; Smith, Brian J.; Holton, Carvel; Glenn, William E.

doi:10.1889/1.1984967

Cited by 15 publications

(11 citation statements)

References 3 publications

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“…Because the differently patterned domains require no separation, diffraction efficiency is increased and the risk of shorts between electrodes is reduced. Bos et al [19] have demonstrated the use of pattern alignment with an optically active device for transmissive SLMs. High contrast and relatively low-operation voltage have been demonstrated.…”

Section: Polarization-independent Lc Phase Gratingsmentioning

confidence: 99%

Nematic LC modes and LC phase gratings for reflective spatial light modulators

Yang

1998

IBM J. Res. & Dev.

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Single-domain nematic liquid crystal (LC) devices based on the polarization-rotation effect, the birefringent effect, or both have been investigated for reflective spatial light modulators (SLMs) which use a polarizing beam splitter to separate the input light beam from its orthogonal output beam. We have evaluated each LC mode in terms of its contrast ratio, optical efficiency, operating voltage, and tolerance to cell-gap nonuniformity. We studied the hybridaligned and the 0"-, 45°-, and 63.6°-twisted nematic LC modes, which can be operated either normally white (NW) or normally black (NB). We have also investigated the mixed twisted nematic (MTN) and self-compensated twisted nematic (SCTN) modes in NW and the tilted homeotropic mode in NB. Twodimensional simulations have also been carried out for both NW and NB modes implemented in active-matrix-driven reflective SLMs to elucidate the effect of fringe fields, which tend to generate disclination lines in high-field on-pixels adjacent to low-field off-pixels. Numerical examples are given to illustrate that, for the NB modes, the disclination lines occurring in the field-on bright state appear dark and reduce the optical efficiency. However, for the NW modes, the disclination lines occurring In the field-on dark states generate a light leakage which degrades the contrast ratio. To improve optical efficiency, we have also studied polarizationindependent LC phase gratings using patterned alignment with opposite twist angles for reflective SLMs. The basic equations for the diffracted and nondiffracted intensities have been derived. The device parameters, operating voltage, and optical efficiency are given for various cases with a twist angle equal to or less than 90°.

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Section: Polarization-independent Lc Phase Gratingsmentioning

confidence: 99%

Nematic LC modes and LC phase gratings for reflective spatial light modulators

Yang

1998

IBM J. Res. & Dev.

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“…The twist sense is determined according to the tilt direction of the surface LC director so that the elastic free energy takes a minimum value. An LC cell with periodic reverse-twist domains is useful for multidomain TN LC displays 6,7 with symmetric view-ing characteristics and LC gratings 8,9 with polarizationindependent diffraction efficiencies. An alternating distribution of an opposite tilt direction can be formed by a photo alignment method 7 and a multirubbing process 6 using a photolithography.…”

Section: Introductionmentioning

confidence: 99%

Periodic reverse-twist nematic domains obtained by microrubbing patterns

Honma

Yamamoto

Nose

2004

Journal of Applied Physics

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A method for forming periodic 90° reverse-twist domains using a microscale rubbing pattern has been proposed; that is, an isolated 90° twist domain is surrounded by a 45° twist domain. Since liquid crystal (LC) materials exhibit elastic nature, the twist sense of the inner 90° twist domain prefers to be the same as that of the surrounding 45° twist domain. Two factors are investigated to obtain periodic 90° reverse-twist domains; (i) the injection process of LC material (isotropic or nematic phase) and (ii) the ratio of the area of the surrounding 45° twist domain and the whole area (the normalized area of the 45° twist domain). In the case of the injection in isotropic phase, it is revealed that periodic 90° reverse-twist domains can be obtained only when the area of the 45° twist domain is sufficiently large. On the other hand, in the case of injection in nematic phase, periodic 90° reverse-twist domains can successfully obtained regardless of the area of the 45° twist domain. Thus, the injection rocess is a very important factor to obtain periodic 90° reverse-twist domains. The fabricated LC cell with the periodic 90° reverse-twist domains is applied to LC grating. The almost linear relationship between the diffraction efficiency and the normalized area of the 45° twist domain is found and the high diffraction efficiency (0.39) near the theoretically maximum value (0.405) is obtained when the normalized area of the 45° twist domain is very small (0.1). The fabricated LC grating can function as a polarization-idependent and wavelength-independent LC grating.

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“…1,2 To control the electric field at required pixels, the active matrix technique that has been developed for direct view liquid crystal displays can be utilized. However, opaque features of the active matrix limit the maximum transmission of this type of device.…”

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confidence: 99%

“…2 For the sake of simplicity, this structure is labeled the ''Reverse-Twist'' grating. Similar to the Orthogonal-Twist configuration, it consists of alternating twisted-nematic domains of opposite twist sense and similar surface orientation.…”

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confidence: 99%