Optical waveguide embedded light redirecting Bragg grating arrangement

A method of forming an embedded permanent optical light redirecting grating in a selected grating region of an elongated solid glass waveguide portion of an optical waveguide, comprising the steps of:

• forming two mutually coherent beams of coherent ultraviolet radiation;
• and
• directing the two beams transversely on the solid glass waveguide portion at respective angles of incidence selected for the beams to be symmetrical relative to a plane extending at an oblique angle relative to a longitudinal axis of the solid glass waveguide portion for the two beams to coherently interfere with one another with attendant generation of an interference pattern having intensity peaks that extend at said oblique angle into and through said grating region and form therein a multitude of permanently embedded grating elements that are disposed at the oblique angle and at a substantially equal longitudinal spacing throughout the grating region and are capable of redirecting light reaching them between a first path extending longitudinally through the solid portion and at least one second path extending externally of the waveguide at an angle relative to the longitudinal axis that depends on the oblique angle with attendant in-phase combination of that light directed in one of the paths against the grating region which has a wavelength within a narrow range around a central wavelength that is in a predetermined relationship to the spacing of the grating elements, in the other of said paths following redirection from the grating elements.