Holograms from surface plasmons.

A group from Osaka University in Japan, led by Satoshi Kawata, has demonstrated a method to make true-color holograms that show the true color from any viewing angle, a near-impossibility with surface-relief holograms and difficult to achieve with conventional reflection or transmission holograms. The method involves recording holograms with red, green and blue lasers on a 150 nm thick photoresist coated on to glass, with a 55 nm layer of silver and a 25 nm silicon dioxide (glass) on top of the photoresist, the whole structure being 230 nm thick. When this is illuminated from behind with white light passed through a prism, the result is the replay of a true color hologram which shows …