Patterned alignment of liquid crystal molecules in silica micro-capillaries

Controllable alignment of liquid crystal molecules inside micro-capillaries is an essential issue to obtain repeatable devices based on photonic liquid crystal fibres. In this paper we describe in detail the photo-alignment technique for micro-capillaries based on sulfuric azo dye SD-1 which allows for stable alignment of liquid crystal molecules in the direction defined by the polarisation of ultraviolet light. Two-step selective irradiation allowed for periodic patterns in which two different alignment configurations were observed simultaneously within a single capillary. The obtained alignment was very stable, even in capillaries as thick as 125 μm of internal diameter.