Developing self-assembled materials for photonic devices

Photonic devices are present in everyday life: from TV screens, holograms, phones, PC displays and fibre optical communications to avionics. All these are examples of photonic devices – devices that are able to manipulate light with an external control. The general objective of this project was to develop new families of photonic devices to manipulate guided and unguided light beams using novel materials.

Eva Otón

Our approach to creating new photonic structures is based on self-assembled materials (SAM). The molecules of SAMs are able to assemble with each other like Lego bricks, creating complex structures. A good example of SAMs is liquid crystals (LCs), whose optical properties can be modulated by external stimuli and thus they are excellent candidates to be implemented in photonic devices.

A crucial key task in the material development of the project involved the stabilization of the so-called Blue Phase LCs. Blue phases are a very particular LC type. Unlike other LC phases that organise with a 1D or 2D order degree, Blue Phases can self-assemble into 3D cubic structures. In previous research Blue Phase cubes were shown to appear disorganised at micrometre size. However, we developed a new technique and obtained perfectly organised large Blue Phase monocrystals. This is a remarkable and completely above expectations achievement, because these materials were not stable as a unique structure outside small temperature ranges. Besides, a 3D Blue Phase monocrystal, being a periodic nanostructure, can be regarded as a photonic crystal; these have become exceptionally popular materials in the last few years due to their unusual optical properties.

One of the most significant and critical tasks of the project was creating photonic devices for unguided light beams. The devices that were fabricated are called beam steerers, which are devices capable of moving light beams (laser beams) towards one direction. Three tuneable beam steerers based on LCs were manufactured: a grating, a prism and a grating-prism. The grating can deviate laser beams to fixed positions; they are not tuned continuously. The prism produces a continuous angular deviation of laser beams but with limited deviation angles. Finally the grating-prism combines both optical functions, it can work as a prism and as a grating at the same time. This combination of refractive and diffractive effects was achieved by the development of a novel multilayer electrode matrix configuration in a liquid crystal device. The grating-prism effectively deviates a light beam to a large fixed angle by diffraction, and then fine-tunes the beam over small angle ranges by refraction. Tuneable photonic devices based on materials like liquid crystals are opening new alternatives for photonic applications, and they become highly coveted when several optical functions can be implemented into one device.

Because of the nature of this project, any progress in these technologies has an impact in Material Sciences and Photonics, as well as societal benefits. Since it is a transversal technology, new developments benefit many areas, like electronics, photonics, space and optical communications. An important feature of these photonic devices is that their tuneability does not require movable parts. This fact is welcomed in many applications, especially in space technologies. Optical non-movable elements are preferred over mechanical ones, specifically during launching or landing stages, when there are high chances of equipment damage. Potential photonic devices, with reduced size, could become an inspiration for new commercial devices. It is expected that the generated experience and know-how will improve other procedures and contribute to a better understanding of the underlying phenomena in self-assembled optical materials and structures.

How did you benefit from the POLONEZ fellowship?

During the project, I achieved significant progress, especially when the tasks required synergy of different areas, since the proposal relied on a multidisciplinary approach. As a result, my learning curve was greatly increased in this respect. I had to learn how to manage many different tasks in parallel and make progress with every task. I also learnt a number of new techniques and know-how which I consider priceless sets of skills both for personal growth and for future career endeavours.

Dr Eva Otón received a B.Sc. degree in chemistry and an M.Sc. degree in material engineering from the Universidad Autónoma de Madrid and Universidad Complutense de Madrid in 2005 and 2008 respectively. She has a background in Material Engineering and Chemistry and her field of expertise since her PhD is Liquid Crystals and Liquid Crystal Devices. She has 5 years of postdoctoral experience, two of these were spent in a research company in Tokyo. Her work has focused mainly in research of SAM structures. After the POLONEZ project she is working at the same research institution at the Military University of Technology, in Poland, continuing the exciting research derived from the project.