Blue Phase Liquid Crystal for photonic applications beyond display 

Problem Definition:

The blue phases (BP) [Fig. 1] of Cholesteric liquid crystals (LC) are liquids that exhibit orientational order characterized by crystallographic space-group symmetries. These topologically elegant LC phases possess intriguing optical properties, which can be tuned electrically, making them a suitable candidate for photonic applications. BP is thermodynamically stable in a very small temperature range of 1 - 2 °C. Recently polymer stabilization has been shown to increase this range to >60 °C (including the room temperature), thus enhancing their appeal in the research community. A whole gamut of features of BPLC depends on the platelets size of the domains, which in turn can be controlled by heating/cooling rates at with which BPs are prepared. Thus controlling heating/cooling rates become a foremost technological challenge in the study of BLPC.


Texture of BPI
Texture of BPII
                                                                                   Fig. 1 Polarization optical micrographs of BPLC under crossed polarizers
                                                                                                                

Objectives:

In the purview of this master thesis the student will start with the implementation of algorithms for achieving precise slow heating/cooling rates of 0.01 °C/min. He/she will prepare LC cells using our clean room facility to perform thorough characterization of the same. Various experiments revolving around measurement of effective refractive index as a function of the applied field, reaction time, angular dependence of the optical properties, temperature stability, spectral behavior etc can then be carried out.


Keywords:

Blue phase liquid crystals, Control theory, Electro-optical characterization, clean room. 

Location:

Ardoyen CMST + at home.