Abstract: A substantially transparent substrate having first and second major surfaces and a plurality of side surfaces; a thin-film semiconductor layer coupled to the first major surface of the substrate and including first and second major surfaces and at least one photo-sensitive p-n junction therein; and a light directing feature operable to cause incident light to propagate through the substrate and into the semiconductor layer in a waveguide mode such that the light reflects a plurality of times between the first and second major surfaces of the semiconductor layer and impinges upon the p-n junction a plurality of times

Abstract: The present invention is directed to a method of enhancing the photosensitivity of an optical waveguide and an optical waveguide having persistent UV photosensitivity following out diffusion of a loading gas such as H2 or D2. The optical waveguide is loaded with a gas such as H2 or D2 to form an associated baseline refractive index. At least a portion of the loaded optical waveguide is exposed to UV radiation to induce a change in the baseline refractive index and the waveguide is annealed to diffuse the gas from the loaded optical waveguide and to stabilize the change in refractive index. Following annealing the optical waveguide retains a UV photosensitivity sufficient to produce significant refractive index changes relative to the induced change in baseline refractive index. The method of the present invention is particularly well suited for designing and fabricating grating devices, tuning grating strength and wavelength, and for providing accurate spatial control of waveguide photosensitivity.

Abstract: In accordance with the invention, a continuously chirped fiber Bragg grating is made by fabricating a continuously chirped phase mask and using the mask to write a Bragg grating on a parallel fiber. The chirped phase mask is made by exposing a photoresist-coated mask substrate to two interfering beams: one a collimated beam and the other a beam reflected from a continuously curved mirror. After etching, the resulting phase mask can be used to write a chirped fiber grating having a continuously varying grating period without physical modification of the fiber. The resulting fiber grating has a widened bandwidth and uniform dispersive delay characteristics useful for dispersion compensation in critical telecommunications applications.