Fabrication of photosensitive strong grating couplers

Abstract

Systems devices and methods in accordance with the invention impart high strength index of refraction patterns to photosensitive optical devices, such as Bragg gratings written in optical fibers. A length of small diameter fiber retaining photosensitivity is fabricated by flame elongation of an optical fiber precursor having dopant containing cladding, using a diffuse, low velocity inverted flame that does not introduce water, OH or H2 into the fiber. By varying the flame velocity during each scan the fiber is diminished to a small, uniform diameter, waist region. Photosensitivity is preserved and enhanced by exposure of the prepared waist region to scanning actinic illumination within an in-diffusing environment of pressurizing hydrogen or deuterium, and controlling the exposure to optimize the photo-induced index change. The photochemistry is balanced to provide a strong index of refraction grating by adjusting illumination instensity and scanning velocity to arrive at a low fraction of a selected photoabsorbing component of the dopant.

Dependencies are inferred from the claim text.