Development of an Active Display Using Plasmonic Nanorods and Liquid Crystals
Doctor of Philosophy
The current generation of display technology has already provided the public with displays that exhibit high color fidelity, faster than the eye can see frame rates, and screens spanning an order of magnitude in size, from hand-held to wall-sized. What has yet to be achieved is for display technology to become versatile, fitting into the human environment in a way that is unobtrusive, ergonomic, and promotes an improved quality of life. This thesis points to nanotechnology, particularly plasmonic nanomaterials, as a way to bring display technologies to that next level. The work presented in this thesis is the development of a nanomaterial that is vividly colored, electronically controllable, and highly versatile in its possible applications. First, an understanding of the electronic switching of nematic liquid crystals is gained via combination of randomly oriented gold nanorods with homogeneously aligned nematic liquid crystal. The nanorods are used to probe the birefringence of the liquid crystal as an in-plane bias is used to switch the alignment of the liquid crystal from a uniform parallel alignment to a 90 degree twisted alignment. This mechanism is confirmed with theoretical modeling using Jones Calculus. Second, the polarization sensitivity of the nanorods is exploited by creating a hexagonal array of co-oriented nanorods to form a plasmonic pixel using electron beam lithography. Aluminum was chosen as the plasmonic material because its plasmon resonance can span the whole visible region, and because of its compatibility with the semiconductor manufacturing industry. The outstanding vivid color of these pixels is dependent on the physical characteristics of the individual nanorods, and also on the inter-rod spacing. Dipole coupling within the array of ~300 nm separated nanorods is used to restrict plasmon scattering at both long- and short-wavelengths. A simple 3-step color control mechanism was developed that others can use to produce aluminum plasmonic pixels with colors on-par with standard red, green, and blue displays. Finally, mm-scale colored pixels are demonstrated to be switchable with a liquid crystal display, and therefore immediately compatible with current liquid crystal display technology.