Convergent beam guided mode technique for use in liquid crystal studies

Abstract

The use of a convergent beam to excite guided modes in a liquid crystal layer in order to determine the director profile is described. The technique has two main advantages over the conventional collimated beam procedure. First, the convergent beam guided mode (CBGM) technique uses a highly focused beam spot that simultaneously excites many guided modes and produces reflectivity data over a wide angle range. Such reflectivity can be captured in milliseconds with a charge coupled device array and can therefore potentially be used to study cell dynamics. Second, the CBGM technique removes the need to rotate the liquid crystal cell and consequently the focused beam remains completely stationary on the liquid crystal layer, allowing examination of single pixels. The work presented here is a demonstration of the CBGM technique via a study of the static director profile of a homogeneously aligned nematic (E7) liquid crystal layer.