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AssigneesFemtonics Corporation, OZ Optics Ltd.
InventorsOmur M. Sezerman, Kenneth O. Hill, Garland Best, Dwayne R. J. Miller, Michael Armstrong, Shujie Lin
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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. This latter process is to accumulate heat to the point of liquefying the material in order to increase material compliance to the femtosecond writing process and increase the subsequent thermal barrier to relaxation of the written structural element and thereby increase the lifetime of the device or structural function. One or more zones of permanently altered refractive index characteristics can be formed in a waveguiding device, such as an optical fiber by utilizing a focused, pulsed, laser light source which generates a focal region having an intensity greater than the threshold for inducing permanent refractive index changes in the device. The focal region is aligned with the device and relative movement between the focal region and the device has the effect of sweeping the focal region across the device in a predetermined path. The result is a zone within the device in which the refractive index characteristics of the device have been permanently altered so as to control amplitude, phase, spatial propagation or polarization states of light within the material.
1 A method for creating a zone of permanently altered refractive index characteristics in an optical waveguiding device made of glass material and having at least one core and at least one cladding, using a beam which is generated by a focused pulsed laser light source having:
The method according to claim 1 wherein said step (b) comprises the steps of:
The method according to claim 1 wherein said laser light source is a laser system in which the output of a frequency-doubled Erbium-doped fiber laser is amplified in a laser regenerative amplifier that is based on a Ti:Sapphire gain material.
The method according to claim 1 wherein said laser light source has a beam diameter of from 0.1 to 10 mm.
The method according to claim 1 wherein said focused pulsed laser light is focused with a lens, axicon, focusing mirror, or combinations thereof to achieve desired spatial relationship of the focal region with respect to the target region.
The method according to claim 1 wherein said pulse width is less than 200 femtoseconds.
The method according to claim 1 wherein larger material restructuring permitted under heat accumulation conditions leads to larger thermal activation barriers for the glass material to relax back to original form and thereby significantly increase the lifetime of any written structure in the material.
The method according to claim 1 wherein said peak pulse intensity threshold for inducing permanent refractive index changes is at least 1010 W/cm2.
The method according to claim 1 wherein said optical waveguiding device is selected from the group of optical waveguiding devices consisting of:
A method for creating a zone of permanently altered refractive index characteristics in an optical waveguiding device made of glass material and having at least one core and at least one cladding, using beams generated by at least two focused pulsed laser light sources, each having:
A method for creating a zone of permanently altered refractive index characteristics in an optical waveguiding device made of glass material and having at least one core and at least one cladding, using beams generated by at least two focused pulsed laser light sources, each having:
An optical waveguiding device having a core, a cladding, and at least a single zone therein at which the refractive index characteristics of the waveguiding device have been permanently altered, whereby the altered waveguiding device can serve as an attenuator, an optical tap, a polarimeter, or a Bragg grating.
An optical attenuator comprising an elongated waveguiding device having a core, a cladding, and an optical transmission axis extending along the waveguiding device, said waveguiding device also comprising a single zone therein wherein the index of refraction of the device has been permanently altered such that a controlled portion of light transmitted along said core is removed therefrom, thereby leaving a controlled remainder of the light propagating in the core.
An optical tap comprising an elongated waveguiding device having a core, a cladding, and an optical transmission axis extending along the waveguiding device, said waveguiding device also comprising a single zone therein wherein the index of refraction of the device has been permanently altered such that a portion of light transmitted along said core is removed therefrom.
An optical polarimeter comprising an elongated waveguiding device having a core, a cladding, and an optical transmission axis extending along the waveguiding device, said waveguiding device also comprising at least two longitudinally spaced apart zones therein wherein the index of refraction of the device has been permanently altered, said zones having azimuthal angles spaced at substantially 90 degrees, and each of said zones being oriented substantially at a Brewster angle relative to said transmission axis, causing it to reflect s-polarized light out of said core, such that said polarimeter is capable of measuring two orthogonal light polarization states therein.
A method for improving coupling between a waveguide and an optical source having characteristic optical mode field properties by modifying the refractive index characteristics of the waveguide at or near the interface point by the method of claim 1 to thereby reshape the waveguide mode field properties to match those of the source.
A method for improving coupling between two waveguides having different refractive index profiles and corresponding optical mode field properties by modifying the refractive index characteristics of at least one of the waveguides at or near the interface point by the method of claim 1 to reshape the mode field properties of said at least one of the waveguides to match the final waveguide mode field properties.
A waveguide collimator comprising a waveguide whose refractive index characteristics have been altered near an end face thereof to substantially enlarge the mode field diameter thereof, thereby reducing the divergence of the light exiting the waveguide.
The method according to claim 1 including the step of initially applying mechanical stress to said waveguiding device and then removing said mechanical stress once said zone of altered refractive index characteristics has been created.
The method according to claim 1 including the step of initially applying an electric field to said waveguiding device and then removing said electric field once said zone of altered refractive index characteristics has been created.
The method according to claim 1 including the step of positioning a volume of index matching fluid between said laser light source and said waveguiding device such that said beam will pass through said fluid prior to reaching said target region.
Dependencies are inferred from the claim text.