Abstract: An oxide bronze host material is a solid solution of a first oxide component comprising molybdenum oxide (MoO.sub.3), tungsten oxide (WO.sub.3), zirconium oxide (ZrO), niobium oxide (Nb.sub.2 O.sub.5) or any two or more thereof and a second oxide component comprising vanadium oxide (V.sub.2 O.sub.5) and/or titanium oxide (TiO.sub.2), the formula ratio of the first and second oxide components being selected such that the host material is capable of accepting guest atoms when incorporated in an electrochemical cell, said guest atoms altering the spectral characteristics of the host material without producing substantial visible color change in thin layers of the host material. Such a material may be used as a thin layer (12) in an electrochemical variable optical density window further including electrode layers (11, 15) on glass supports (10, 16) and an electrochromic oxide bronze layer (14) spaced from the layer (12) by an electrolyte layer (13a, 13b).

Abstract: A controllable optical waveguide includes a core through which light can propagate and cladding around the core, at least one of the core and cladding having plural portions made of a material having a refractive index which varies in response to an applied electric field. A plurality of electrode pairs are arranged so as to each be able to apply an electric field to a respective one of the portions of the material in a manner effecting a change in its refractive index. Each electrode pair includes two electrodes which each have a plurality of fingers, the fingers of one electrode of each pair being interdigitated with those of the other electrode of the pair. As the electric field produced by a given electrode pair varies, the refractive index of the corresponding portion of the material varies in a manner causing the waveguide to retain light or to allow light to escape through such portion.

Abstract: A thin, flexible, portable device (11) may be used as a credit card. The device is encapsulated by front and rear plastics layers. Viewed from the front the device comprises a first electrode of a transparent electrically conductive layer (13); a layer (14) of an electrochromic, metal-sensitive compound which is capable of dissolving metal atoms and which changes color in so doing; a layer of a solid, fast ion conducting electrolyte (15); a second layer of electrochromic material (16), acting as a second electrode; and a layer of electrically conductive material (17). The solid electrolyte layer (15) is substantially non-conductive at room temperature but is highly conductive of metal ions at a raised temperature. To erase information, the entire device is heated to 150.degree. C., and a potential difference is applied between the front electrode (14) and the rear electrode (16), driving all metal atoms out of the front electrochromic material into the rear electrode (16).

Abstract: An electrochromic device in the form of a cell comprising a metal-sensitive compound having a thickness of 1 micrometer or less, preferable between 0.5 and 0.05 of a micrometer, is described in contact with a solid fast ion conductor as electrolyte. The fast ion conductor itself is in contact with an electrode capable of providing ions the same as the fast ions of the conductor.

Abstract: An electrochromic device in the form of a cell comprising a first electrode, a metal-sensitive transistion metal oxide in contact with the first electrode and a solid fast ion conductor as the electrolyte in contact with the oxide.