Micro-photonic structures for efficient light collection and distribution

Problem Definition:

A new research area that is rapidly gaining importance, is the use of liquid crystals for the management of light distribution or collection. The main applications are more efficient solid-state (LED) lighting luminaires, active daylighting and efficient solar concentrators for photovoltaic energy conversion. For a good example of active daylighting see the Lightcatcher by Econation.

The main building block for such systems is based on a component that allows the active deviation of a light beam. The most straightforward principle is based on wedge-shaped optical structures with variable refractive index. Preliminary research is presently taking place at CMST in collaboration with LCP and B-Phot (VUB). In a subsequent phase of this research we intend to use blazed gratings (structures with a sawtooth shaped cross-section) with different shape parameters and that will serve as a recipient for confining the liquid crystal material. Therefore, it is necessary to produce in an accurate and reproducible way such structures according to arbitrarily chosen shape parameters. Because of the relatively high thickness of the liquid crystal layer, we will use the so-called 'blue phase' mode, which maintains a sufficiently high switching speed, even for very thick layers.

Principle of light steering

Possible application: luminaires with flexible illumination patterns

Blue phase arrangement (source commons.wikimedia.org )

Micrograph of the blue phase (source www-g.eng.cam.ac.uk)

Display based on BPLC (Courtesy of Samsung)

Polymer microstructures made using laser ablation


The objective of this thesis is the development of a technology based on laser ablation with which blazed grating structures can be made with freely chosen shape parameters. Several host materials will be tried, and for each material a thorough characterization of the laser ablation process must be performed. This will result in a set of design rules that will allow a designer to start working. If the acquired results allow it, a first active test vehicle will be made with which active light steering can be demonstrated. This will imply – besides the laser ablation process – the application of a transparent conductor (ITO), cell filling with the liquid crystal / monomer mixture and the establishment of the blue phase condition.


technology, laser ablation, liquid crystal, characterisation


Ardoyen CMST