Liquid Crystal Technologies for Laser-based Imaging Applications

A key objective is to develop new liquid crystal (LC) technologies for laser-based imaging applications, including reducing distortion from spatially varying interference in images formed with lasers (speckle). The high brightness, directionality, and wide colour gamut of coherent light from laser sources makes it a very desirable resource for many applications (e.g., communications and imaging). However, this coherence can generate problems, such as a spatially varying interference in an image, which is commonly known as speckle. Successful removal of this speckle would enable lasers to be used in a range of biomedical, projection and head-up display technologies.

The most common method to reduce speckle is via a device producing multiple statistically independent speckle patterns. Existing devices typically use moving mechanical parts, (e.g., ground glass diffusers) to scatter the light and produce the statistically independent patterns. However, such approaches have size, weight, power, and cost limitations that constrain widespread use. Liquid crystals (LCs) are potentially desirable materials to combat speckle as their combination of optical anisotropy and response to electric fields means that they are able to produce partially decorrelated speckle patterns without having any mechanically moving parts. Such devices have the potential to be much smaller than existing devices and achieve a vibration-free solution, therefore providing much wider commercial applicability.

An aim of this project is to develop new LC devices that can reduce the appearance of laser speckle in a range of different applications including laser projection, biomedical imaging, and head-up display technologies. For each of the applications identified, testbeds will be developed, and the most successful LC devices will be incorporated to highlight their commercial impact. Optimised devises consisting of phase masks derived from Hadamard Matrices will be considered as a means to achieving statistically independent speckle patterns with the application of an electric field. This project aims to produce a range of different phase masks at different layers within a LC device using the additive manufacturing process of laser writing, removing the need for moving mechanical parts as different phase masks will be accessed by applying various electric fields. This laser writing manufacturing technique will then be used to explore and create alternative LC devices for potential applications in other laser-based photonics applications. This project falls within the EPSRC theme of Engineering and is closely aligned with the Photonic materials, Light Matter Interaction and Phenomena, Optical Devices and Subsystems, Optoelectronic Devices and Circuits sub-themes.