Evolutionary development of advanced liquid crystal spatial light modulators

Collings, N.; Crossland, W. A.; Ayliffe, P.; Vass, D.G.; Underwood, Ian

doi:10.1364/ao.28.004740

Cited by 115 publications

(32 citation statements)

References 12 publications

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“…In combination with silicon back planes, such devices have already been used in projection applications and spatial light modulators. 6 Thus in this article we also report on the development of novel ferroelectric liquid crystals and their potential for use in fast, high-resolution, low-voltage ferroelectric liquid crystal on silicon (LCOS) devices with optimised performance. Such light processors can be used in amplitude modulation or phase modulation mode.…”

Section: Introductionmentioning

confidence: 99%

The influence of an alkenyl terminal group on the mesomorphic behaviour and electro-optic properties of fluorinated terphenyl liquid crystals

et al. 2010

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Novel liquid crystal terphenyls with two, three and four lateral fluoro substituents and an alkene unit at the end of a terminal chain are presented in terms of synthesis, mesomorphic behaviour and electrooptic properties. The difluoro analogues were found to exhibit the smectic C phase over a wide temperature range, with short temperature ranges of the smectic A and the nematic phase above. Very low melting points were recorded for the trifluoro analogues, and the shorter chain homologues of these materials exhibit the nematic phase over a wide temperatures with a monotropic smectic C phase and the higher homologues exhibit the smectic C phase over a wide temperature range with the nematic phase above. The tetrafluoroterphenyls exhibit the nematic phase over a wide temperature range with the complete absence of smectic phases. As appropriate, the materials were evaluated for dielectric anisotropy and threshold voltage in nematic phase, and mixed with a chiral dopant to evaluate the spontaneous polarisation, tilt angle and switching times in the chiral smectic C phase. The results show that these compounds are strong potential candidates for application in both vertically aligned nematic (VAN) and ferroelectric liquid crystal (FLC) devices.

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Section: Introductionmentioning

confidence: 99%

The influence of an alkenyl terminal group on the mesomorphic behaviour and electro-optic properties of fluorinated terphenyl liquid crystals

et al. 2010

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“…[71][72][73] These pulses are binary in nature and are applied to the LC. In this case, different average voltage levels are implemented using pulse width modulation on the basis that LCs respond to the RMS value of the applied voltage waveform.…”

Section: Sram-based Pixel Circuitrymentioning

confidence: 99%

“…Therefore, this approach is not suitable for the phase modulation. Soon afterward, the first field effect nematic LCOS device 27 was reported, and the first fast ferroelectric LC on silicon (FLCOS or FLC-LCOS) device was demonstrated by Collings et al 28 In the early days of optical computing, LCOS was proposed as an amplitude screen 29 for spatial filtering in optical correlators. 30 At that time, it was realized that phase modulation of incident light beam could be possibly used in the future.…”

Section: Brief Introduction To Lcos Devicesmentioning

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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“…The origins of liquid crystal over silicon (LCOS) are shrouded in mystery and are difficult to trace (1)(2)(3)(4); however, ferroelectric liquid crystal (FLC)-based LCOS devices are relatively easy, with the invention being shared between the groups at Boulder Colorado (5-7), STC labs in Harlow (8) and Edinburgh University (9,10). The presentation of the first working devices by STC labs at an Optical Society (OSA) spatial light modulators (SLMs) meeting in Lake Tahoe in 1988 (11) was the beginning of this technology, with the design and fabrication of a 176×176 pixel device (9).…”

Section: Introductionmentioning

confidence: 99%

Ferroelectric liquid crystal over silicon devices

Wilkinson

2012

Liquid Crystals Today

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Over the past 20 years, ferroelectric liquid crystal over silicon (FLCOS) devices have made a wide impact on applications as diverse as optical correlation and holographic projection. To cover the entire gamut of this technology would be difficult and long winded; hence, this paper describes the significant developments of FLCOS within the Engineering Department at the University of Cambridge.The purpose of this paper is to highlight the key issues in fabricating silicon backplane spatial light modulators (SLMs) and to indicate ways in which the technology can be fabricated using cheap, low-density production and manufacturability. Three main devices have been fabricated as part of several research programmes and are documented in this paper. The fast bitplane SLM and the reconfigurable optical switches for aerospace and telecommunications systems (ROSES) SLM will form the basis of a case study to outline the overall processes involved. There is a great deal of commonality in the fabrication processes for all three devices, which indicates their potential strength and demonstrates that these processes can be made independent of the SLMs that are being assembled. What is described is a generic process that can be applied to any silicon backplane SLM on a die-by-die basis. There are hundreds of factors that can affect the yield in a manufacturing process and the purpose of a good process design procedure is to minimise these factors. One of the most important features in designing a process is fabrication experience, as so many of the lessons in this business can only be learned this way. We are working with the advantage of knowing the mistakes already made in the flat panel display industry, but we are also faced with the fact that those mistakes took many years and many millions of dollars to make.The fabrication process developed here originates and adapts earlier processes from various groups around the world. There are also a few totally new processes that have now been adopted by others in the field. Many, such as the gluing process, are still on-going and have to be worked on more before they will fully suit 'manufacturability'.

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Evolutionary development of advanced liquid crystal spatial light modulators

Cited by 115 publications

References 12 publications

The influence of an alkenyl terminal group on the mesomorphic behaviour and electro-optic properties of fluorinated terphenyl liquid crystals

The influence of an alkenyl terminal group on the mesomorphic behaviour and electro-optic properties of fluorinated terphenyl liquid crystals

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

Ferroelectric liquid crystal over silicon devices

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