Abstract: The present invention is directed to the creation of optical waveguiding devices from standard optical fibers by the creation of zones of permanently altered refractive index characteristics therein. A high intensity femtosecond laser beam is focused at a predetermined target region in the fiber so as to soften the glass material at the target region. After aligning the focal region with the target region in the fiber there will be relative movement between the focal region and the fiber, which has the effect of sweeping the focal region across the fiber in a predetermined path, so as to create a secondary waveguide path. A portion of the light traveling along the core is removed from the core along the secondary waveguide path such that the device can be utilized as an attenuator, an optical tap, or a polarimeter.

Abstract: The present invention is directed to the creation of optical waveguiding devices from standard optical fibers by the creation of zones of permanently altered refractive index characteristics therein. A high intensity femtosecond laser beam is focused at a predetermined target region in the fiber so as to soften the glass material at the target region. After aligning the focal region with the target region in the fiber there will be relative movement between the focal region and the fiber, which has the effect of sweeping the focal region across the fiber in a predetermined path, so as to create a secondary waveguide path. A portion of the light traveling along the core is removed from the core along the secondary waveguide path such that the device can be utilized as an attenuator, an optical tap, or a polarimeter.

Abstract: The present invention is directed to the creation of optical waveguiding devices from standard optical fibers by the creation of zones of permanently altered refractive index characteristics therein. A high intensity femtosecond laser beam is focused at a predetermined target region in the fiber so as to soften the glass material at the target region. After aligning the focal region with the target region in the fiber there will be relative movement between the focal region and the fiber, which has the effect of sweeping the focal region across the fiber in a predetermined path, so as to create a secondary waveguide path. A portion of the light traveling along the core is removed from the core along the secondary waveguide path such that the device can be utilized as an attenuator, an optical tap, or a polarimeter.

Abstract: The invention relates to an optical fiber polarizer comprising an optical fiber with at least a core, a cladding and surrounding medium (or outer cladding) where one or more sections of the optical fiber include periodic/aperiodic (chirped, quasi-periodic) modulation of the dielectric properties of the fiber in the direction of propagation of the light (the longitudinal axis of the fiber). The modulation of the dielectric properties of the fiber is such that it introduces periodic/aperiodic birefringence along the direction of propagation of the light, such a modulation usually but not necessarily being confined to the vicinity of the core region of the fiber. Means are included to attenuate preferentially some of the modes of propagation of the fiber, specifically modes of one principal state of polarization and not the orthogonal state of polarization.

Abstract: The present invention is directed to the creation of optical waveguiding devices from standard optical fibers by the creation of zones of permanently altered refractive index characteristics therein. A high intensity femtosecond laser beam is focused at a predetermined target region in the fiber so as to soften the glass material at the target region. After aligning the focal region with the target region in the fiber there will be relative movement between the focal region and the fiber, which has the effect of sweeping the focal region across the fiber in a predetermined path, so as to create a secondary waveguide path. A portion of the light traveling along the core is removed from the core along the secondary waveguide path such that the device can be utilized as an attenuator, an optical tap, or a polarimeter.

Abstract: The present invention is directed to the creation of optical waveguiding devices from standard optical fibers by the creation of zones of permanently altered refractive index characteristics therein. A high intensity femtosecond laser beam is focused at a predetermined target region in the fiber so as to soften the glass material at the target region. After aligning the focal region with the target region in the fiber there will be relative movement between the focal region and the fiber, which has the effect of sweeping the focal region across the fiber in a predetermined path. The result is a zone within the fiber in which the refractive index characteristics of the fiber have been permanently altered so as to control amplitude, phase, spatial propagation or polarization states of light within the material.

Abstract: The present invention is directed to the creation of zones of permanently altered refractive index characteristics in glass waveguiding devices, including optical fibers and optical waveguides pre-existed in a glass substrate. Such zones in which the refractive index has been permanently altered are created in glass using a very high intensity laser beam which is produced by focusing the light output from an ultrafast pulsed laser at a predetermined target region in the glass. The preferred laser is a Ti:Sapphire amplified, frequency-doubled Erbium-doped fiber laser system, providing light pulses of approximately 100 femtosecond duration, each with an energy of between about 1 nanojoule and 1 millijoule, and preferably at a pulse repetition rate of between 500 Hz and 1 GHz. The repetition rate is chosen to deliver pulses faster than the thermal diffusion time over the dimensions of the volume element being modified.

Abstract: A method of trimming fused-tapered couplers, with or without in-fiber Bragg gratings, to form multiplexers, demultiplexers or combinations of both, by either or both of (1) increasing the phase differential between the symmetric and asymmetric supermodes by irradiating one or both ends of the coupler with UV radiation confined transversely to between the cores of the fibers, and (2) decreasing the phase differential between the modes by irradiating a portion of one or both ends of the coupler with two beams of UV radiation, each confined transversely to include a corresponding core and excluding a significant fraction of the space between the cores.

Abstract: Unbalanced Mach-Zehnder interferometers (MZI) are useful for a number of applications including wavelength filters, gain flattening or gain equalization elements, and band splitters or combiners. A MZI is comprised of two couplers surrounding a phase shifting region, which consists of two arms with differential propagation constants. We disclose a means of using light exposure to unbalance a symmetric MZI consisting of substantially the same lengths of substantially the same fiber. In particular, the index of refraction of a fiber can be increased by exposure to ultraviolet light, and the magnitude of the change can be increased by using higher germanium doping or by hydrogen loading the fiber. The magnitude of the phase shift can be controlled accurately by varying the fiber length exposed, the light exposure intensity, the light exposure time, and the hydrogen loading or fiber composition.

Abstract: An polarization compensator is disclosed for passing light in a predetermined wavelength range. The compensator has unequal output orthogonal polarizations for light launched into the device within a specific wavelength range. A waveguide having a blazed grating having a blaze angle &thgr;bl of between 20° and 45° with respect to the optical axis of the waveguide exhibits a tap efficiency difference for orthogonal polarizations for offsetting and lessening a polarization dependence of the device. This waveguide is optically coupled with the optical device requiring polarization compensation. The grating is oriented about its optical axis to lessen the inequality in output orthogonal polarizations for light launched into the optical device.

Abstract: A method is disclosed wherein optical structures such as Bragg gratings can be written into planar waveguides disposed on a substrate. By employing the method of this invention, a polarization insensitive device can be made. Such relatively thin planar waveguides disposed on a substrate are inherently polarization sensitive and the structure itself is birefringent. By writing structures in the waveguides or by simply writing a refractive index change in the waveguide by limiting the beam width at the waveguide layer to less than or equal to the thickness of the waveguiding layers on the substrate, in combination with conventional wider beam writing techniques, polarization sensitivity can be lessened or obviated.

Abstract: A method is disclosed wherein optical structures such as Bragg gratings can be written into planar waveguides disposed on a substrate. By employing the method of this invention, a polarization insensitive device can be made. Such relatively thin planar waveguides disposed on a substrate are inherently polarization sensitive and the structure itself is birefringent. By writing structures in the waveguides or by simply writing a refractive index change in the waveguide by limiting the beam width at the waveguide layer to less than or equal to the thickness of the waveguiding layers on the substrate, in combination with conventional wider beam writing techniques, polarization sensitivity can be lessened or obviated.

Abstract: A method is disclosed wherein optical structures such as Bragg gratings can be written into planar waveguides disposed on a substrate. By employing the method of this invention, a polarization insensitive device can be made. Such relatively thin planar waveguides disposed on a substrate are inherently polarization sensitive and the structure itself is birefringent. By writing structures in the waveguides or by simply writing a refractive index change in the waveguide by limiting the beam width at the waveguide layer to less than or equal to the thickness of the waveguiding layers on the substrate, in combination with conventional wider beam writing techniques, polarization sensitivity can be lessened or obviated.

Abstract: Light is coupled out of a first mono-mode optical waveguide such as an optical fiber an into another single mode waveguide through a substantially planar slab waveguide. The first mono-mode optical waveguide has a grating impressed within which has refractive index perturbations that reflect predetermined wavelengths of incident light out of a portion of a side of the optical waveguide adjacent the grating; The slab planar waveguide has an end optically coupled to the portion of the first mono-mode optical waveguide, for guiding light coupled out of the side of the waveguide, and for maintaining a uni-phase wavefront of said light by having a response that confines the light to a single mode in one dimension, and multi-mode in another dimension and allows at least a portion of the light to converge.

Abstract: A method of fabricating a strongly photosensitive optical waveguide is comprised of locally heating at least a portion of a weakly photosensitive optical waveguide for a period of time sufficient to increase the density of defects associated with photosensitivity in the heated portion of the waveguide core.

Abstract: An index grating is imprinted in the core of an optical fiber using a specially designed silica glass phase grating mask. The phase mask is held in close proximity to the optical fiber. Laser irradiation of the phase mask with ultraviolet light at normal incidence imprints (photoinduces) into the optical fiber core the interference pattern created by the phase mask.

Abstract: Efficient, narrow-band rocking filters have been made in polarization-maintaining monomode optical fiber by photoinducing periodic birefringent gratings along the length of the fiber. These gratings, fabricated with a period chosen to provide synchronous coupling between the two principal states of polarization of the LP.sub.01 mode at a preselected wavelength, gently rock to and fro the principal polarization axes of the fiber. To photoinduce the grating, the fiber is exposed periodically along its length to a U.V. light beam which is incident at right angles to the geometrical axis of the fiber and is directed .pi./4 radians with respect to the principal axes. Efficient polarization mode conversion at 1.3 .mu.m with the fiber gratings are obtained.

Abstract: A two-channel optical fiber fused coupler comprising two optical fibers, each with a core and cladding, fused together at a narrow tapered waist. The first channel is at a wavelength of .lambda..sub.1 and the second channel is at a wavelength of .lambda..sub.2 where .lambda..sub.2 is longer than .lambda..sub.1. The coupler is fabricated to have a characteristic wavelength .lambda..sub.0 such that for wavelengths .lambda..sub.2 longer than .lambda..sub.0 coupling occurs and for wavelenghts .lambda..sub.1 shorter that .lambda..sub.0 the light at .lambda..sub.1 is core guided throughout the coupler and thus does not couple across.

Abstract: This invention relates to a method of creating an index grating in an optical fiber comprising disposing a slit mask containing one or more slits over a side of an optical fiber, illuminating the fiber through the slit mask by substantially monochromatic ultraviolet light for a short interval, whereby an index grating line is created and stored in the core of the fiber.

Abstract: An index grating is imprinted in the core of an optical fiber using a specially designed silica glass phase grating mask. The phase mask is held in close proximity to the optical fiber. Laser irradiation of the phase mask with ultraviolet light at normal incidence imprints (photoinduces) into the optical fiber core the interference pattern created by the phase mask.