GRATING-COUPLED LIQUID-CRYSTAL WAVE-GUIDE

A waveguide consisting of a thin (< 1 mum) layer of nematic liquid cry stal sandwiched between two parallel aligned gratings is described. Gr ating coupling to guided modes is demonstrated by monitoring the refle ction and transmission from the cell as a function of incident angle. A reduced birefringence is seen compared to the bulk case which is exp lained in terms of disordered regions of liquid crystal close to the g rating surfaces. The movement of guided modes under electrical bias is shown and time resolved experiments demonstrate high contrast switchi ng with rise times as fast as 18 mus.