High speed spatial light modulators with analogue phase control for next generation imaging, photonics, and laser manufacturing

Liquid crystal (LC) technology has become a dominant force in the displays market. To date, a lot of research and development has been focussed in optimising the LC material properties for displays; however, there are an increasing number of other non-display applications that could benefit from LC technology if it were used to modulate the phase of the light rather than its intensity. Specifically, a dynamic optical element based upon LC technology that can modulate the phase rapidly and with analogue control will be of significant importance in the development of next-generation adaptive optics (AO) for a range of technologies whereby aberration correction and/or dynamic parallelisation are required. Notable advances have already been made using AO in areas such as microscopy, optical tweezing, holographic projection, and laser machining. For example, AO is expanding the capabilities of biomedical microscopy by enabling imaging of biological process in thick and even live tissue specimens, through compensation of aberrations. Such research is now being extended to super-resolution microscopy, which reveals cellular structures an order of magnitude lower than the diffraction limit. AO devices are also used for opto-genetics and photo-activation, where it is necessary to reconfigure 3D light fields at high speeds so that specific cells can be selectively activated. New and improved LC devices would therefore enable a range of research that underpins the life and medical sciences. Equally, adaptive control of ultra-fast lasers for optical nano-fabrication would benefit considerably from new LC technology, allowing pulse shaping and parallelisation at high speeds to be realised, supporting future advances in high-value manufacturing. The potential of using dynamic optical elements, such as LC devices, in all of these applications is well substantiated, but current performance is constrained by the switching speeds and/or phase modulation capabilities of the display-type devices. Increasing device speed will satisfy an as-yet unmet demand from these applications and could enable a greater impact in all of these application areas. Moreover, the development of a new fast-switching SLM with analogue phase control may potentially pave the way to new application spaces that are yet to be realised.

The true impact of this proposal lies in the delivery of a new electro-optical effect which is fundamentally compatible with LCoS technology, delivers greater than 2pi phase depth (minimum of 8 levels) and has a frame rate in excess of 500Hz. Such an effect will revolutionise many different applications which have been, up till now, been held back by modulation technology. The results of this project will help to further expand the potential impact of many techniques and application which use the phase of the light rather than the amplitude, allowing diffraction and interference to be the means of light manipulation. The true extent of these applications has only just begun, and their likely effect on the world and industry of photonics will be substantial.

The impact of this proposed work will be both multidisciplinary as well as cover a variety of different output mechanisms. Figure A shows the mechanism behind delivering such revolutionary new materials across all three Universities. The combination of chemistry, physics and engineering is an essential mix which will help to guarantee success. The diagram in Figure A also demonstrates the materials design cycle which ensures a continuous flow of new materials and experimental feedback which is a vital aspect of this type of project. The academic route of publication in world open access leading journals will continue and the successfully optimised novel materials, devices and embodiments in applications will be filed as intellectual property. This approach allows both academic progressions in the field as well as the potential for industrial development. Examples of the success of these applications in the commercial world can already be seen through partnerships such as optical tweezing and the development of start-up companies such as Light Blue Optics.

The economic impact of this proposal is very significant as modern technology is placing an every increasing demand on different types of laser devices and systems. Recently we have seen LCoS based holograms move into commercial projection displays (both front and rear) with huge success, proving truly exceptional performance in terms of colour and compactness. A major limitation of these displays is in the phase modulation technology. This is a continuous progression that no other technology can come close to, especially at the cost and compactness of these soft materials. Given more and more areas are using lasers as sources for visibility, sensing, characterisation or treatment, these novel devices are an ideal, cheap technology for integration. The ability of make these versatile structures through very simple procedures and yet still allow a total variety of different effects and enhancements take place is perhaps the core advantage of these materials and devices.

A significant hurdle in designing and developing these materials is the lack of a custom silicon backplane. Without a deep knowledge of the materials and their performance, it is very difficult to commit the significant resources required to designing a custom silicon backplane. Hence in this project we will avoid this major cost and target test structures which replicate the properties of an LCoS device without the expense. We have already had discussions with major backplane manufacturers such as Hamamatsu, AU Optronics, Jasper and HiMax. All four of these companies came back with the same response, that they would be very interested in such a material and would consider integrating it into their backplanes, but they would require a very definitive experimental demonstration of the materials first. Hence this is one of the key objectives of this project which will then lead on to the integration into a commercial LCoS device.