Harvard College

Qinetiq Limited

University of Exeter

Peter Vukusic

Joanna Aizenberg

Christopher Robert Lawrence

John Roy Sambles

Robert Howe

The rolled photonic fibers presents two codependent, technologically exploitable features for light and color manipulation: regularity on the nanoscale that is superposed with microscale cylindrical symmetry, resulting in wavelength selective scattering of light in a wide range of directions. The bio-inspired photonic fibers combine the spectral filtering capabilities and color brilliance of a planar Bragg stack compounded with a large angular scattering range introduced by the microscale curvature, which also decreases the strong directional chromaticity variation usually associated with flat multilayer reflectors. Transparent and elastic synthetic materials equip the multilayer interference fibers with high reflectance that is dynamically tuned by longitudinal mechanical strain. A two-fold elongation of the elastic fibers results in a shift of reflection peak center wavelength of over 200 nm.

Band-gap tunable elastic optical multilayer fibers

An iridescent material comprises a diffraction grating incorporating a plurality of sheets () of a first substantially transparent material in parallel alignment and spaced away apart by quantities of a second substantially transparent material (), the second material having a refractive index significantly lower than the refractive index of the first material, the plates being tilted at an angle &#x3b8; to an axis X and the grating having a period d(X) in the direction of axis X, the angle &#x3b8; and period d being such that a second diffraction grating is provided along an axis Z, perpendicular to axis X, the second diffraction grating having a period d(Z) and consisting of ten periods or less and whereby, the diffraction conditions of the grating can be simultaneously fulfilled by electromagentic radiation of a range of wavelength thereby causing iridescence. Materials according to the invention have applications in inter alia document security, anti-counterfeiting measures, artwork, gift wrapping paper and cards and clothing design.

Iridescent materials and devices

A multilayer surface comprising at least two layers, said layers having different refractive indexes such that selective wavelengths/colours are transmitted and or reflected. The layers are preferably laid onto a transparent substrate. The surface can be used as an anti-counterfeit device. A method of determining whether an article is counterfeit comprising: providing such a surface; determining its transmission/absorption characteristics of particular colour(s); matching these up with the expected characteristics to determine whether the surface is counterfeit. This may comprise observing the reflected or transmitted colour at two different angles of incidence or detecting changes in the polarisation state of transmitted light.

Growing community of inventors

Exeter, United Kingdom

Peter Vukusic