An optical waveguide is constructed so as to comprise a non-solid core layer surrounded by a solid-state material. The non-solid core layer has an index of refraction which is lower than the index of refraction of the surrounding solid-state material, and light can be transmitted with low loss through...http://www.google.com/patents/US20060008227?utm_source=gb-gplus-sharePatent US20060008227 - Apparatus for optical measurements on low-index non-solid materials based on arrow waveguides
