Optical Fredericks Transition in a Nematic Liquid Crystal Layer

Abstract

One of the most fascinating aspects of liquid crystals is the Fredericks transition, which can occur when a finite sample of nematic liquid crystal is subjected to an externally applied magnetic or electric field. It is well-known that the director orientation throughout a sample of liquid crystal may be affected by a sufficiently strong magnetic or electric field. More specifically, the director alignment throughout a thin sample of nematic liquid crystal will not be influenced by the external magnetic or electric field when its magnitude is less than the critical field strength or Fredericks threshold, but will be influenced by the external field and start to adjust its orientation whenever the magnitude of the field is above the critical field strength. This change in the director alignment after the magnitude of the field increases beyond the critical field strength is called the Fredericks transition. It is exactly this important aspect of liquid crystals that provides many applications of liquid crystals for displays.