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OwnerLeon Poladian, Justin L Blows +1inventors
InventorsLeon Poladian, Justin L Blows, Graham R Atkins
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The present invention provides a method of inducing a change in refractive index of a photosensitive material. The method comprises the step of simultaneously exposing a region of the material to first and second radiations having first and second wavelengths respectively and being selected, in combination, to induce the change in refractive index in the region, and wherein the first and second wavelengths differ from each other. In one embodiment, the region is a first core (42) of a multiple-core optical fibre (40). The first radiation (48) is propagated along the first core (42) and the second radiation (46) is used to illuminate the first core from outside the fibre (40) through a phase mask (52). This embodiment enables an optical grating to be written in the first core (42) without inducing refractive index changes in the closely-adjacent second core (44).
A method of inducing a change of refractive index in a photosensitive material comprising:
A method as claimed in any one of the preceding claims wherein the photosensitive material includes an outer plastics coating and the photosensitive material is exposed to the second radiation through the outer plastics coating, the wavelength of the second radiation being selected to pass through the plastics coating substantially without absorption.
A method as claimed in any one of the preceding claims, wherein each of the first and second wavelengths is selected to be ineffective alone in inducing a further change in the photosensitive material.
A method as claimed in any one of the preceding claims, wherein the first and second radiations are provided from the same source.
A method as claimed in any one of the preceding claims, wherein the method further comprises the steps of setting up an interference pattern with a first beam of the first radiation in the material, and exposing the material to a second beam of the second radiation so as to induce the refractive index change in the material where the interference pattern and the second beam overlap.
A method as claimed in any one of the preceding claims, wherein at least one of the first and second wavelengths is chosen from a range of visible wavelengths.
A method as claimed in any one of the preceding claims, wherein the photosensitive material comprises germanium-doped glass, and wherein combined photon energies of the first and second radiations are selected to excite a 185 nm absorption band in the germanium-doped glass.
A method as claimed in any one of the preceding claims, wherein the step of inducing the refractive index change in the region comprises absorbing the first and second radiations mediated by a real transition level of the photosensitive material.
An optical device incorporating a photosensitive material in which a refractive change has been induced in the photosensitive material using a method in accordance with any one of the preceding claims.
A method of inducing a change of refractive index in a photosensitive material substantially as herein described with reference to the accompanying drawings.
An optical device substantially as herein described with reference to the accompanying drawings.
Dependencies are inferred from the claim text.