A method and apparatus for forming a Bragg grating using a high intensity light includes a pair of focussed writing beams 26,34 that simultaneously intersect and interfere with each other at a region 30 of a photosensitive optical fiber 28. The beams 26,34 have a high intensity (e.g., at least about 500 mjoules/cm.sup.2) and pass through an interface medium 50 that is substantially transparent to the wavelength of the writing beams 26,34. The medium has a thickness T set such that the intensity of the beams at the surface 56 of the medium 50 is below an surface damage intensity such that no ablations occur on the fiber 28 or the surface 56 when the fiber 28 is exposed to the beams 26,34.
CROSS REFERENCES TO RELATED APPLICATIONS
Copending U.S. patent applications, Ser. No. 09/205,845, entitled "Method and Apparatus For Forming A Tube-Encased Bragg Grating" filed contemporaneously herewith, contains subject matter related to that disclosed herein.
A method and system for the controlled irradiation of optical fibers in a process for fabricating optical fiber components such as Bragg grating devices. A beam of ultraviolet light is passed through a narrow slit in a mask to form a narrow beam of light. The narrow beam is focused into a line image that is directed onto the optical fiber to produce a photo-induced refractive index change in the optical fiber. The intensity and configuration of the line image as it impinges the optical fiber is controlled to reduce detrimental effects to the fiber.
A laser device, in particular a semiconductor laser, emitting optical radiation with a defined mode pattern can be produced from a standard Fabry-Perot (FP) laser by post-processing at the wafer level, i.e. before the wafer is separated into individual dies by cleaving/dicing. A sub-cavity is formed within the FP laser cavity. The sub-cavity has a predetermined length and is located between the FP facets. An aperiodic grating composed of a small number of contrast elements, typically less than 10, with predetermined inter-element separations and predetermined spacings relative to the sub-cavity is formed on or in the optical waveguide. The inter-element separations and the spacings relative to the sub-cavity produce a filtering function of the aperiodic grating for optical radiation propagating in the waveguide. The laser device is suitable for telecommunications applications due to its high side-mode-suppression ratio and narrow-linewidth.
A method is provided for precise and repeatable location of one or more Bragg gratings in a large diameter optical waveguide having a cross-section of at least about 0.3 millimeters, featuring the steps of: defining a reference location on a fixed placement datum arranged on a waveguide fixture device; defining one or more desired locations on a large diameter optical waveguide arranged on the waveguide fixture location in relation to the reference location; and writing one or more Bragg gratings in the large diameter optical waveguide at the one or more desired locations based on the reference location on the fixed placement datum. The step of defining the reference location may include marking the fixed placement datum with a scribe mark thereon; and securing the fixed placement datum in a groove in a waveguide fixture device.
Methods for recording volume Bragg grating structures having a target wavelength are disclosed. Such a method may include providing a photosensitive recording medium, bringing a first face of the recording medium into contact with a face of a prism, the prism being made of a material that is transparent at a recording wavelength, and recording a Bragg grating onto the recording medium by exposing the prism to an incident light wave at the recording wavelength.
A fiber Bragg grating may be written at an arbitrary wavelength without extensive recalibration or reconfiguration of the writing equipment in some embodiments. A pair of writing beams may be used to expose the fiber. The crossing angles of the writing beams may be adjusted.
