Holographic optical switching: the "ROSES" demonstrator

Crossland, W. A.; Manolis, Ilias; Redmond, M.M.; Tan, K.L.; Wilkinson, Timothy D.; Holmes, M.J.; Parker, Tom; Chu, Hong‒Son; Croucher, J.; Handerek, V.A.; Warr, Stephen; Robertson, Brian; Bonas, I.G.; Franklin, Ross; Stace, C.; White, Henry; Woolley, Richard A. J.; Henshall, Gordon D.

doi:10.1109/50.908753

Cited by 123 publications

(44 citation statements)

References 11 publications

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“…This technique was used in the UK ROSES optical switches project. 36 However, as mentioned for an FLC-LCOS system, the loss is too high and is doubled when the fibers are optically coupled at both the input and output ports of a switch. 99 Nematic LC devices avoid most of these diffraction efficiency losses.…”

Section: Algorithms Of Hologram Generation For Phase-only Lcos Devicementioning

confidence: 99%

“…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%

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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: Algorithms Of Hologram Generation For Phase-only Lcos Devicementioning

confidence: 99%

Section: Lc Phases For Phase-only Lcos Devicesmentioning

confidence: 99%

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

2014

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“…For Ax = 161[xm, An was calculated by using (5) resulting An = 21 andfor Ax = 321[xm, An = 45. Therefore, the device is a 1 x 8X router in case of CWDM and 1 x4l router for DWDM systems (Crossland et al 2000).…”

Section: Wavelength Routermentioning

confidence: 99%

“…To avoid small misalignments, along the x axis of the output fibers array position, with impact in the efficiency, we can optimize the hologram pattern introducing an offset in the bars position to correct them (Crossland et al 2000). An offset of 5% of the hologram period would impact the efficiency up to a 40%.…”

Section: Computer Generated Holograms (Cgh's) Designmentioning

confidence: 99%

Tunable holographic components in WDM optical networks

Minguez

Horche

2010

Opt Quant Electron

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This paper describes the applications of a multipurpose holographic device in optical networks with Coarse and Dense Wavelength Division Multiplexing (CWDM/ DWDM) technologies. In its basic structure, it can operate as a tunable wavelength filter, wavelength multiplexer or X router. By using a more complex structure, the device works as OADM (Optical Add Drop Multiplexer) or OS (Optical Switch). Some simulations of the basic devices, from the optical transmission point of view, are made to match the transmission parameters for the application in optical networks. Performance parameters of the device, like switching time, losses, cross-talk or polarization insensitivity are analyzed and compared with other multiplexing or switching technologies. To complete the review of these components, a study of computer generated holograms (CGH) design is carried out. The results are used in the design of holographic devices to perform different applications: in Metro networks, where a design of a holographic device with wavelength conversion and routing is analyzed, or, in Access Networks like a tunable filter or demultiplexer in Fiber to the Home/Business (FTTH/FTTB) topologies.

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“…The second generation of SLMs was designed for use in optical telecommunications switching, where optical efficiency was important and frame rate was not. Hence, the reconfigurable optical switches for aerospace and telecommunications systems (ROSES) (19) chips were designed to have a much simpler interface and were only a one-dimensional (1D) device to match the design of the holographic optical switch (20). The objective was to build on previous processing techniques, enabling the demonstrator SLM to be fabricated using the same processing setup for the FB-SLM and to emulate the high device yield seen so far.…”

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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Holographic optical switching: the "ROSES" demonstrator

Cited by 123 publications

References 11 publications

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

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

Tunable holographic components in WDM optical networks

Ferroelectric liquid crystal over silicon devices

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