The Applications and Technology of Phase-Only Liquid Crystal on Silicon Devices

Collings, N.; Davey, T; Christmas, Jamieson; Chu, Daping; Crossland, Bill

doi:10.1109/jdt.2010.2049337

Cited by 84 publications

(45 citation statements)

References 89 publications

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“…The maximum diffraction efficiency of an FLC device can be obtained only when the correct thickness of the device is applied and a 90 6 switching angle is used. 36 Nevertheless, 90 6 FLC materials are rare and are much slower than the more common 45 6 FLC materials. Large quantization noise (the continuous phase profile can only be quantized into discrete values due to the limited number of discrete voltages that the silicon backplane can apply) is another problem for FLC-LCOS devices.…”

Section: Lc Phases For Phase-only Lcos Devicesmentioning

confidence: 99%

“…Although the subframe sequential technique is used to achieve different voltage levels and multi-level modulation that are available in FLC-LCOS holographic projection, 37 this technique loses at least half of the incident light to symmetric diffraction orders. Moreover, it was observed that the maximum light efficiency (,50%) could be only achieved if the FLC switching angle was 90 6 . This angle requires highly specialized materials that tend to slow the response time such that the devices are comparable to the responses times of the nematic phase-only LCOS devices operating in the ECB electro-optic effect.…”

Section: Ssflcsmentioning

confidence: 99%

“…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.…”

Section: Brief Introduction To Lcos Devicesmentioning

confidence: 99%

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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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Section: Lc Phases For Phase-only Lcos Devicesmentioning

confidence: 99%

Section: Ssflcsmentioning

confidence: 99%

Section: Brief Introduction To Lcos Devicesmentioning

confidence: 99%

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

2014

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“…In the former case, the amplitude modulation is enabled by projecting the output state of polarization onto an output linear polarizer. This was the case with previous liquid crystal display (LCD) technologies or, in general, with liquid crystal related devices when used in display applications [22,23]. In the application of WSS systems, phase modulation is preferred for better light usage efficiency.…”

Section: Analysis On Lcos For the Wss Systemmentioning

confidence: 99%

LCoS SLM Study and Its Application in Wavelength Selective Switch

et al. 2017

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Abstract:The Liquid-Crystal on Silicon (LCoS) spatial light modulator (SLM) has been used in wavelength selective switch (WSS) systems since the 1990s. However, most of the LCoS devices used for WSS systems have a pixel size larger than 6 µm. Although there are some negative physical effects related to smaller pixel sizes, the benefits of more available ports, larger spatial bandwidth, improved resolution, and the compactness of the whole system make the latest generation LCoS microdisplays highly appealing as the core component in WSS systems. In this review work, three specifications of the WSS system including response time, crosstalk and insertion loss, and optimization directions are discussed. With respect to response time, the achievements of liquid crystal material are briefly surveyed. For the study of crosstalk and insertion loss, related physical effects and their relation to the crosstalk or insertion loss are discussed in detail, preliminary experimental study for these physical effects based on a small pixel LCoS SLM device (GAEA device, provided by Holoeye, 3.74 µm pixel pitch, 10 megapixel resolution, telecom) is first performed, which helps with predicting and optimizing the performance of a WSS system with a small pixel size SLM. In the last part, the trend of LCoS devices for future WSS modules is discussed based on the performance of the GAEA device. Tradeoffs between multiple factors are illustrated. In this work, we present the first study, to our knowledge, of the possible application of a small pixel sized SLM as a switching component in a WSS system.

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“…For implementation of the switching plane in a WSS, liquid-crystal-on-silicon (LCoS)-based spatial light modulators (SLMs) [21]- [24] offer several advantages over previous technologies, and have become increasingly popular in recent years.…”

Section: Introductionmentioning

confidence: 99%

Wavelength-Selective Switches for Mode-Division Multiplexing: Scaling and Performance Analysis

Ho¹,

Kahn²,

Wilde³

2014

J. Lightwave Technol.

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Abstract-Wavelength-selective switches for modedivision-multiplexing systems are designed by scaling switches from single-mode systems. All modes at a given wavelength are switched as a unit, which is necessary in systems with substantial mode coupling, and minimizes the numbe r of ports required to accommodate a given traffic volume. When a pure mode is present at the input, modal transmission and coupling coefficients are modedependent and may be computed using a simple modeclipping model. When multiple modes are present, interference between modes alters the transmission and coupling coefficients, shifting the passband center frequency and changing its bandwidth. Mode-coupling matrices are used to compute mixed modes having the narrowest or widest bandwidths, or having the largest center-frequency offsets. In a specific design for gradedindex fiber, five mode groups and 50-GHz channel spacing, the one-sided bandwidth may change up to  3.6 GHz. In a system with many cascaded switches and strong mode coupling, the end-to-end response per switch may be characterized by a mode-averaged transmission coefficient.Index Terms-Wavelength-selective switch, multimode fiber, mode-division multiplexing.

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The Applications and Technology of Phase-Only Liquid Crystal on Silicon Devices

Cited by 84 publications

References 89 publications

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

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

LCoS SLM Study and Its Application in Wavelength Selective Switch

Wavelength-Selective Switches for Mode-Division Multiplexing: Scaling and Performance Analysis

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