Sidewall control of multistate switchable photonic devices

Lead Research Organisation: Nottingham Trent University
Department Name: School of Science & Technology


The development of multilevel, multistable switchable phase structures is of significant importance for photonic switching since bi/multistability in optical telecommunications switches will enable (i) enhanced network security after a power outage, since the device would continue to operate and be optically transparent, and (ii) redundancy management, where semi permanent re-routing can easily be implemented. In this project, we build on recent work where we have demonstrated the possibility of not only bistability, but multistability, by micro-structuring the sidewall in a planar aligned liquid crystal layer in order to control alignment. Such azimuthal bistability has previously been reported in liquid crystal devices using surface gratings, surface bi-gratings and periodic arrays of posts on one of the confining substrates. However, in the proposed work the use of the sidewall avoids the need for index matching with surface structures and allows for more functionality in the substrate surface, for instance so that it can be used as an active waveguide cladding. The collaboration between an applied mathematician, Dr Mottram (Strathclyde University), and a materials physicist, Dr Brown (Nottingham Trent University), has allowed this new approach to develop from theoretical possibility to a practical demonstration of feasibility. The proposed project seeks funding to create novel structures that possess stable static states, to investigate dynamic switching between the states, and to investigate the optical and diffractive properties of multistable structures.


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Davidson AJ (2010) Defect trajectories and domain-wall loop dynamics during two-frequency switching in a bistable azimuthal nematic device. in Physical review. E, Statistical, nonlinear, and soft matter physics

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Evans C (2011) Sidewall Controlled Multistable Nematic Liquid Crystal Devices in Molecular Crystals and Liquid Crystals

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Ladak S (2009) Sidewall control of static azimuthal bistable nematic alignment states in Journal of Physics D: Applied Physics

Description Switching between bistable states of a device with sawtooth sidewalls was achieved and investigated using dual-frequency materials. A simplified model of the liquid crystal device, using only a director-based approach, was developed, initially to be used only as a way of creating initial conditions for the more complicated Q-tensor model. However, this simple model matched surprisingly well with the Q-tensor model, even during dynamic switching of the system, and was considerably less intensive in terms of computer resources.
Exploitation Route Low ambient power displays.
Sectors Digital/Communication/Information Technologies (including Software)

Description Our expertise in bistable nematic liquid crystal device fabrication, developed through this project, was used in a short consultancy contract to prove a patent concept for an I.P.R exploitation company (2013)
First Year Of Impact 2011
Sector Electronics