Optics of structured metal layers with liquid crystals

Ebbesen et al published in Nature in 1998 observations on the remarkable optical transmission properties of metal films perforated with an array of holes which have diameter much less than the radiation wavelength. This study has subsequently stimulated an enormous surge of research interest into the exploration of enhanced transmission of electromagnetic radiation through a variety of different metal structures. Indeed the whole area of surface plasmon optics, of which this enhanced transmission is but a part, has seen massive growth. It is generally perceived that the use of such structures has potential in optical chip technology, optical sensing, displays, organic light emitting devices [OLEDs], single photon sources, novel directed light sources; enhanced detector capabilities etc. The essence of almost all perceived structures is the combination of a perforated metal screen (holes or slits, which actually often support very different electromagnetic behaviour) and thin films of dielectric. Generally the structures considered thus far have been passive in so far as their dielectric parameters may not be tuned. (OLED's are clearly not passive but this is simply carrier creation). Of course if the thin film dielectric is optically non-linear and the optical fields intense enough then there is the obvious possibility of non-linear switching, but this is likely to require high brightness sources. Here we wish to explore the potential for the combined use of liquid crystals, which may have their optical permittivities altered by low voltages (as in liquid crystal displays [LCDs]), combined with structured metal films.