Fiber optic beam delivery for selectable intensity profiles

Abstract

A beam delivery device is configured to generate a selectable intensity profile from a beam. The device includes a first length of optical fiber having a first refractive index profile (RIP) and a second length of optical fiber having a second RIP different from the first RIP. The second length of optical fiber includes a coaxial confinement region, which is configured to confine at least a portion of a conditioned beam. The confined portion corresponds to one of different intensity profiles. The intensity profile is established by corresponding states in different perturbation states applied to the device, so that the confined portion is configured to provide a selected intensity profile in the selectable intensity profiles at an output end of the second length of optical fiber.

Description

[0001] This application is a divisional application of the invention patent application with application number 201880047416.5, application date March 28, 2018, and invention name “Fiber optic beam transmission device for generating optional intensity profile”. Technical Field

[0002] The technology disclosed herein relates to fiber lasers and fiber-coupled lasers. More specifically, the disclosed technology relates to methods, devices and systems for adjusting and maintaining adjusted beam characteristics (spot size, divergence profile, spatial profile or beam shape, etc. or any combination thereof) at the output end of a fiber laser or a fiber-coupled laser.

[0003] Related Applications

[0004] This application is a continuation-in-part of each of the following applications: U.S. Patent Application Nos. 15 / 607,399, 15 / 607,410, and 15 / 607,411, filed on May 26, 2017; and International Application PCT / US2017 / 034848. Each of these applications claims the benefit of U.S. Provisional Patent Application No. 62 / 401,650, filed on September 29, 2016. All of these applications are incorporated herein by reference in their entirety. Background Art

[0005] The use of high-power fiber-coupled lasers continues to gain popularity in a variety of applications, such as material processing, cutting, welding, and / or additive manufacturing. These lasers include, for example, fiber lasers, disk lasers, diode lasers, diode-pumped solid-state lasers, and lamp-pumped solid-state lasers. In these systems, optical power is transmitted from the laser to the workpiece via an optical fiber.

[0006] Various fiber-coupled laser material processing tasks require different beam characteristics (e.g., spatial profile and / or divergence profile). For example, cutting thick metals and welding generally require larger spot sizes than cutting thin metals. Ideally, the characteristics of the laser beam would be adjustable to achieve optimized processing for these different tasks. Conventionally, users have two choices: (1) employ a laser system with fixed beam characteristics, which can be used for different tasks but is not optimal for most tasks (i.e., a trade-off between performance and flexibility); or (2) purchase a laser system or accessory that provides variable beam characteristics but adds significant cost, size, weight, complexity, and may result in reduced performance (e.g., optical loss) or reduced reliability (e.g., reduced robustness or reduced uptime). Currently available laser systems that are capable of changing beam characteristics require the use of free-space optics or other complex and expensive additional mechanisms (e.g., zoom lenses, mirrors, translatable or motorized lenses, combiners, etc.) to change the beam characteristics. No solution provides the desired adjustability of beam characteristics that minimizes or eliminates reliance on the use of free-space optics or other additional components that impose considerable penalties in cost, complexity, performance, and / or reliability. What is needed is an in-fiber device for providing varying beam characteristics and shapes that does not require or minimizes the use of free-space optics and that avoids significant cost, complexity, performance tradeoffs, and / or reduced reliability. Summary of the invention

[0007] The present disclosure is summarized by the following exemplary embodiments. Further aspects and advantages will become apparent from the following detailed description of the embodiments which proceeds with reference to the accompanying drawings.

[0008] Example embodiment 1: A beam delivery device configured to generate a selectable intensity profile from a beam, the beam delivery device comprising: a first length of optical fiber, the first length of optical fiber having a first refractive index profile (RIP), the first RIP being capable of modifying the beam in response to an applied perturbation to form a modulated beam, the modulated beam defining different intensity profiles at an output end of the first length of optical fiber based on different states of the applied perturbation; and a second length of optical fiber, the second length of optical fiber having an input end coupled to the output end of the first length of optical fiber, the second length of optical fiber being formed with a coaxial confinement region, the coaxial confinement region defining a second RIP different from the first RIP, the coaxial confinement region being configured to confine at least a portion of the modulated beam, the confined portion corresponding to one of the different intensity profiles, and the one intensity profile being established by a corresponding state in the different states of the applied perturbation, so that the confined portion is configured to provide a selected intensity profile of the selectable intensity profiles at an output end of the second length of optical fiber. In some examples of the device, the selected output intensity profile is Gaussian, super Gaussian, flat-top, saddle, or annular.

[0009] Example embodiment 2: The light beam delivery device according to the aforementioned example 1, wherein the selected intensity profile is a Gaussian intensity profile.

[0010] Example embodiment 3: The optical beam delivery device according to the aforementioned example 2, wherein the corresponding state of the different states of the applied perturbation that establish the Gaussian intensity profile includes an undisturbed state of the first length of optical fiber.

[0011] Example embodiment 4: The light beam delivery device according to the aforementioned example 2, wherein the central core of the coaxial confinement region is configured to provide the confined portion with the Gaussian intensity profile.

[0012] Example embodiment 5: The light beam delivery device according to the aforementioned example 1, wherein the selected intensity profile is a super-Gaussian intensity profile.

[0013] Example embodiment 6: A light beam transmission device according to the aforementioned example 1 or 5, wherein the coaxial confinement region includes a central core and an annular region surrounding the central core, and the corresponding states in the different states of the applied disturbance are states of moving, expanding, or simultaneously moving and expanding the light beam when forming the adjusted light beam, so that the intensity distribution generated at the input end of the second length of optical fiber spatially overlaps with adjacent parts of the central core and the annular region.

[0014] Example embodiment 7: The light beam delivery device according to the above example 1, wherein the selected intensity profile is a flat-top intensity profile.

[0015] Example embodiment 8: The light beam delivery device according to the aforementioned example 1, wherein the selected intensity profile is a saddle-shaped intensity profile.

[0016] Example embodiment 9: A light beam transmission device according to any one of the aforementioned examples 1, 5 or 8, wherein the coaxial confinement region includes a central core and an annular region surrounding the central core, and the intensity distribution spatially overlaps with an outer portion of the central core and an inner portion of the annular region.

[0017] Example embodiment 10: The light beam delivery device according to the above example 1, wherein the selected intensity profile is an annular intensity profile.

[0018] Example Embodiment 11: The beam delivery device according to any of the preceding examples 1, 8 or 10, wherein the selected intensity profile includes local minima between bimodal local maxima.

[0019] Example embodiment 12: A beam shaper system, comprising: a laser source, the laser source is used to provide a beam; a variable beam characteristic (VBC) fiber, the variable beam characteristic fiber comprising a first length fiber and a second length fiber coupled to each other, the first length fiber and the second length fiber respectively having a first refractive index profile (RIP) and a second refractive index profile (RIP) different from each other, the first RIP is capable of modifying the beam in response to a disturbance applied to the VBC fiber to form an adjusted beam that can be adjusted based on different states of the applied disturbance, the adjusted beam presents an intensity distribution at the input end of the second length fiber, and the second RIP is defined by a coaxial confinement region, the coaxial confinement region is configured to confine at least a portion of the adjusted beam corresponding to the one intensity distribution; and a controller, the controller is operably coupled to the VBC fiber and is configured to control different states of the disturbance so as to establish different optional intensity profiles, the confined portion of the adjusted beam is configured to provide the different optional intensity profiles at the output end of the second length fiber.

[0020] Example Embodiment 13: The beam shaper system of preceding Example 12, wherein one of the different selectable intensity profiles is a Gaussian intensity profile.

[0021] Example Embodiment 14: The beam shaper system of preceding Example 12, wherein one of the different selectable intensity profiles is a super-Gaussian intensity profile.

[0022] Example Embodiment 15: The beam shaper system of preceding Example 12, wherein one of the different selectable intensity profiles is a saddle-shaped intensity profile.

[0023] Example Embodiment 16: The beam shaper system of preceding Example 12, wherein one of the different selectable intensity profiles is an annular intensity profile.

[0024] Example embodiment 17: A method for generating different beam shapes defined by optional intensity profiles from a light beam, the method comprising: receiving the light beam at a variable beam characteristic (VBC) fiber, the variable beam characteristic (VBC) fiber comprising a first length fiber and a second length fiber coupled to each other, the first length fiber and the second length fiber respectively having a first refractive index profile (RIP) and a second refractive index profile (RIP) different from each other, the first RIP being capable of modifying the light beam in response to a selected perturbation state applied to the VBC fiber to form an adjusted light beam that can be adjusted based on the applied selected perturbation state, and the second RIP being defined by a coaxial confinement region, the coaxial confinement region being configured to confine at least a portion of the adjusted light beam; applying a first perturbation state to the VBC fiber to establish a first selected intensity profile at an output end of the second length fiber; and applying a second perturbation state different from the first perturbation state to the VBC fiber to establish a second selected intensity profile different from the first selected intensity profile at the output end of the second length fiber.

[0025] Example Embodiment 18: The method of preceding Example 17, wherein the first selected intensity profile is substantially a Gaussian intensity profile and the second intensity profile is substantially a super-Gaussian profile.

[0026] Example embodiment 19: The method according to the aforementioned example 17, wherein the second disturbance state is a disturbance magnitude greater than the disturbance magnitude of the first disturbance state.

[0027] Example Embodiment 20: The method of preceding Example 17, wherein the first selected intensity profile is substantially a saddle-shaped intensity profile, and the second intensity profile is substantially a ring-shaped intensity profile.

[0028] Further example embodiments: A computer or machine readable medium for implementing a device, system or apparatus, or having stored thereon instructions for a processor, which when executed, performs any of the example methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The same reference numerals in the accompanying drawings represent the same elements, and these drawings are included in and constitute a part of this specification, and together with the specification, explain the advantages and principles of the technology disclosed herein.

[0030] Figure 1 shows an exemplary optical fiber structure for providing a laser beam with variable beam characteristics;

[0031] Figure 2 depicts a cross-sectional view of an exemplary optical fiber structure for delivering a light beam having variable beam characteristics;

[0032] Figure 3 An example method of perturbing an optical fiber structure for providing a light beam having variable beam characteristics is shown;

[0033] Figure 4 is a graph showing the lowest order mode (LP) calculated for the first length of fiber for different fiber bending radii. 01 )’s spatial profile;

[0034] Figure 5 shows an example of a two-dimensional intensity distribution at a junction when the optical fiber used to change the characteristics of the beam is nearly straight;

[0035] Figure 6 shows an example of a two-dimensional intensity distribution at a node when an optical fiber used to change beam characteristics is bent at a radius selected to preferentially excite a specific confined area of ​​a second length of optical fiber;

[0036] Fig. 7A , 7B and 7C together show Figure 2 The second length optical fiber structure receives at its input end a signal having an intensity distribution (at Fig. 7A ), which is formed by substantially not perturbing the fiber structure so that the second length exhibits a Gaussian intensity distribution at its output end (at Figure 7B ) and the corresponding intensity profile (in Figure 7C )

[0037] Fig. 8A , 8B and 8C show Figure 2 The second length optical fiber structure receives at its input end a signal having an intensity distribution (at Fig. 8A ) is formed by a low to moderate amount of perturbation applied to the fiber structure so that the second length exhibits a super-Gaussian intensity distribution at its output end (at Figure 8B ) and a corresponding intensity profile that can be adjusted to approximate an idealized flat-top intensity profile (shown in the schematic diagram of Figure 8C)

[0038] Fig. 9A , 9B and 9C show Figure 2 The second length optical fiber structure receives at its input end a signal having an intensity distribution (at Fig. 9A ), which is formed by a further perturbation applied to the fiber structure so that the second length exhibits a saddle-shaped intensity distribution at its output end (at Fig. 9B ) and the corresponding intensity profile (in Fig. 9C )

[0039] Fig. 10A , 10B and 10C together show Figure 2 The second length optical fiber structure receives at its input end a signal having an intensity distribution (at Fig. 10A ), which is formed by a further perturbation applied to the fiber structure so that the second length exhibits a ring-shaped intensity distribution at its output end (at Fig. 10B ) and the corresponding intensity profile (in Fig. 10C )

[0040] Figure 11-16 A cross-sectional view showing an exemplary first length of optical fiber for implementing beam characteristic adjustment in an optical fiber assembly;

[0041] Figure 17-19 A cross-sectional view showing an exemplary second length of optical fiber ("limiting fiber") for limiting tailored beam characteristics in a fiber optic assembly;

[0042] Fig. 20 and 21 a cross-sectional view showing an exemplary second length of optical fiber for varying the divergence angle of an adjusted light beam in a fiber optic assembly and confining the adjusted light beam in a fiber optic assembly configured to provide variable beam characteristics;

[0043] Fig.22A An exemplary laser system including a fiber optic assembly configured to provide variable beam characteristics between a feed fiber and a processing head is shown;

[0044] Fig. 22B An exemplary laser system including a fiber optic assembly configured to provide variable beam characteristics between a feed fiber and a processing head is shown;

[0045] Fig.23 An exemplary laser system including a fiber optic assembly configured to provide variable beam characteristics between a feed fiber and a plurality of processing fibers is shown;

[0046] Fig.24 shows examples of various perturbation components for providing variable beam characteristics according to various examples provided herein;

[0047] Fig.25 An exemplary process for adjusting and maintaining modified characteristics of a light beam is shown;

[0048] Figure 26-28 is a cross-sectional view illustrating an exemplary second length of optical fiber ("limiting fiber") for limiting tailored beam characteristics in a fiber optic assembly; and

[0049] Fig.29 is a block diagram of a beam shaper configured to generate a beam shape based on a selected intensity profile. DETAILED DESCRIPTION

[0050] As used throughout this disclosure and in the claims, the singular forms "a", "an", and "the" include the plural forms unless the context clearly dictates otherwise. In addition, the term "comprising" means "including". Furthermore, the term "coupled" does not exclude the presence of intervening elements between coupled items. Furthermore, the terms "modify" and "adjust" are used interchangeably to mean "change".

[0051] The systems, devices, and methods described herein should not be construed as limiting in any way. Instead, the present disclosure relates to all novel and non-obvious features and aspects of the various disclosed embodiments, both individually and in various combinations and sub-combinations with one another. The disclosed systems, methods, and devices are not limited to any particular aspect or feature or combination thereof, nor do the disclosed systems, methods, and devices require the presence of any one or more specific advantages or problem-solving. Any theories of operation are for ease of explanation, but the disclosed systems, methods, and devices are not limited to these theories of operation.

[0052] Although the operations of some disclosed methods are described in a particular order for ease of presentation, it should be understood that this description includes rearrangement unless the specific language stated below requires a specific order. For example, operations described in sequence may be rearranged or performed simultaneously in some cases. In addition, for simplicity, the accompanying drawings may not show the various ways in which the disclosed systems, methods, and devices can be used in conjunction with other systems, methods, and devices. In addition, this specification sometimes uses terms such as "produce" and "provide" to describe the disclosed methods. These terms are high-level abstractions of the actual operations performed. The actual operations corresponding to these terms will vary depending on the specific implementation and are easily discernible by those of ordinary skill in the art.

[0053] In some examples, values, processes, or devices are referred to as "lowest," "optimal," "minimum," etc. It should be understood that such descriptions are intended to indicate that a selection may be made among the many functional alternatives used, and that such selections are not necessarily better, lesser, or superior to other selections. Examples are described with reference to directions indicated as "above," "below," "upper," "lower," etc. These terms are used for convenience of description, but do not imply any particular spatial orientation.

[0054] definition

[0055] Definitions of words and terms used in this document:

[0056] 1. The term "beam characteristic" means one or more of the following terms used to describe a beam. Generally, the beam characteristic of most interest depends on the specifics of the application or optical system.

[0057] 2. The term "beam diameter" is defined as the distance across the center of the beam along the axis for which the irradiance (intensity) is equal to 1 / e of the maximum irradiance 2 While the examples disclosed herein generally use beams that propagate in an azimuthally symmetric pattern, elliptical or other beam shapes may be used, and the beam diameter may differ along different axes. A circular beam is characterized by a single beam diameter. Other beam shapes may have different beam diameters along different axes.

[0058] 3. The term "spot size" is the distance from the center point of maximum irradiance to 1 / e 2 The radial distance (radius) of the point.

[0059] 4. The term "beam divergence distribution" is the power versus the full cone angle. This quantity is sometimes called the "angular distribution" or "NA distribution."

[0060] 5. Terminology The "beam parameter product" (BPP) of a laser beam is defined as the product of the beam radius (measured at the beam waist) and the beam divergence half angle (measured in the far field). The units of BPP are usually mm-mrad.

[0061] 6. "Confinement fiber" is defined as an optical fiber having one or more confinement regions, wherein the confinement region includes a high refractive index region (core region) surrounded by a low refractive index region (cladding region). The RIP of a confinement fiber may include one or more high refractive index regions (core regions) surrounded by a low refractive index region (cladding region), wherein light is guided in the high refractive index region. Each confinement region and each cladding region may have any RIP, including but not limited to step refractive index and gradient refractive index. The confinement regions may be concentric or non-concentric and may be of various shapes, such as circular, annular, polygonal, arcuate, elliptical or irregular shapes, etc. or any combination thereof. The confinement regions in a particular confinement fiber may all have the same shape or may be different shapes. In addition, the confinement regions may be coaxial or may have axes that are offset relative to each other. The confinement region may have a uniform thickness in the longitudinal direction around the central axis, or the thickness may vary in the longitudinal direction around the central axis.

[0062] 7. The term "intensity distribution" generally refers to the light intensity as a function of position. When referring to the light intensity along a line (1D, see e.g. Figure 7C , 8C , 9C and 10C), the specific term "intensity profile" is preferred. When referring to the intensity of light along a plane (2D, see e.g. Figure 7B , 8B , 9B and 10B), the more general term "intensity distribution" is used. In either case, the line or plane is generally perpendicular to the direction of propagation of the light. This is a quantitative property. In addition, the term "beam shape" is used to describe the spatial aspects of the profile (e.g., in a saddle-shaped profile), but is also used to describe the spatial aspects of the distribution (e.g., in a ring-shaped distribution). The skilled person will understand that the aforementioned terms are sometimes used interchangeably, depending on the context. Therefore, some additional qualitative characteristics of certain beam shapes are shown in the accompanying drawings and described in the following paragraphs.

[0063] 8. "Brightness" is a photometric measurement of the luminous intensity per unit area of ​​light propagating in a given direction.

[0064] 9. "M 2 The beam quality factor (also called beam quality factor or beam propagation factor) is a dimensionless parameter used to quantify the beam quality of a laser beam. 2 = 1 is a diffraction-limited beam, and a larger M 2 Values ​​corresponding to lower beam quality. M 2 Equal to BPP divided by λ / π, where λ is the wavelength of the light beam in microns (if BPP is expressed in mm-mrad).

[0065] 10. The term "numerical aperture" or "NA" of an optical system is a dimensionless number that characterizes the angular range over which the system can accept or transmit light.

[0066] 11. The term "light intensity" is not an official (SI) unit, but is used to express the incident power per unit area on a surface or through a plane.

[0067] 12. The term "power density" refers to the optical power per unit area, although this is also called "optical intensity".

[0068] 13. The term "radial beam position" refers to the position of a beam in an optical fiber measured relative to the center of the fiber core in a direction perpendicular to the fiber axis.

[0069] 14. "Radiance" is the radiation emitted per unit area of ​​a light source (e.g., a laser) per unit solid angle in a given direction. Radiance can be varied by changing the beam intensity profile and / or the beam divergence profile or profile. The ability to change the radiance profile of a laser beam implies the ability to change the BPP.

[0070] 15. The term "refractive index profile" or "RIP" refers to the refractive index as a function of position along a line perpendicular to the fiber axis (1D) or in a plane perpendicular to the fiber axis (2D). Many optical fibers are azimuthally symmetric, in which case the 1D RIP is the same for any azimuth.

[0071] 16. "Step-index fiber" has a RIP that is flat (refractive index is independent of position) within the fiber core.

[0072] 17. A "gradient-index optical fiber" has a RIP in which the refractive index decreases with increasing radial position (ie, with increasing distance from the center of the fiber core).

[0073] 18. "Parabolic refractive index fiber" is a special case of gradient refractive index fiber, in which the refractive index decreases quadratically with increasing distance from the center of the fiber core.

[0074] Optical fibers for changing the properties of light beams

[0075] Disclosed herein are methods, systems, and apparatus configured to provide an optical fiber operable to provide a laser beam having variable beam characteristics (VBC) that can reduce the cost, complexity, optical loss, or other disadvantages of the conventional methods described above. Such VBC fibers are configured to vary a variety of beam characteristics. These beam characteristics can be controlled using VBC fibers, thereby allowing a user to adjust various beam characteristics to suit the specific requirements of various laser processing applications. For example, VBC fibers can be used to adjust: beam diameter, beam divergence profile, BPP, intensity profile, M2 factor, NA, light intensity, power density, radial beam position, radiance, spot size, etc., or any combination thereof.

[0076] In general, the disclosed techniques entail coupling a laser beam into an optical fiber, wherein the characteristics of the laser beam in the optical fiber may be adjusted by perturbing the laser beam and / or perturbing a first length of optical fiber (e.g., bending the optical fiber or introducing one or more other perturbations) in any of a variety of ways, and maintaining the adjusted beam characteristics in whole or in part in a second length of optical fiber. The second length of optical fiber is specifically configured to maintain and / or further modify the adjusted beam characteristics. In some cases, the second length of optical fiber maintains the adjusted beam characteristics by delivering the laser beam to its end use (e.g., material processing). The first length of optical fiber and the second length of optical fiber may include the same or different optical fibers.

[0077] The disclosed technology is compatible with fiber lasers and fiber-coupled lasers. Fiber-coupled lasers typically transmit their output via a delivery fiber with a step-index profile (RIP), i.e., with a flat or constant refractive index within the fiber core. In practice, the RIP of the delivery fiber may not be perfectly flat, depending on the design of the fiber. The important parameter is the core diameter (d core ) and NA. The core diameter is typically in the range of 10-1000 microns (although other values ​​are possible) and the NA is typically in the range of 0.06-0.22 (although other values ​​are possible). The delivery fiber from the laser can be routed directly to the processing head or workpiece, or can be routed to a fiber-to-fiber coupler (FFC) or fiber-to-fiber switch (FFS) that couples light from the delivery fiber into a processing fiber that transmits the beam to the processing head or workpiece.

[0078] Most material processing tools, especially those with high power (>1kW), use multimode (MM) fiber, but some material processing tools use single-mode (SM) fiber, which is located in the d core and low end of the NA range. The beam characteristics of SM fibers are uniquely determined by the fiber parameters. However, beam characteristics from MM fibers can vary (unit to unit and / or based on laser power and time) depending on the beam characteristics from the laser source coupled into the fiber, the launch or splicing conditions of the fiber, the fiber RIP, and the static and dynamic geometry of the fiber (bends, coiling, motion, microbends, etc.). For both SM and MM delivery fibers, the beam characteristics may not be optimal for a given materials processing task and are unlikely to be optimal for a range of tasks, which motivates the desire to be able to systematically vary the beam characteristics to tailor or optimize for a specific processing task.

[0079] In one example, a VBC fiber may have a first length and a second length and may be configured to be inserted as an intra-fiber device between a delivery fiber and a processing head to provide the desired adjustability of the beam characteristics. In order to be able to adjust the beam, a perturbation device and / or assembly is disposed near and / or coupled to the VBC fiber and is responsible for perturbing the first length of the beam such that the characteristics of the beam change in the first length of the fiber and the changed characteristics are maintained or further changed as the beam propagates in the second length of the fiber. The perturbed beam is emitted into the second length of the VBC fiber, which is configured to maintain the adjusted beam characteristics. The first length of the fiber and the second length of the fiber may be the same or different fibers and / or the second length of the fiber may include a limiting fiber. The beam characteristics maintained by the second length of the VBC fiber may include any of the following: beam diameter, beam divergence distribution, BPP, intensity distribution, brightness, M 2 factor, NA, light intensity, power density, radial beam position, radiance, spot size, etc. or any combination thereof.

[0080] Figure 1 An exemplary VBC fiber 100 is shown for providing a laser beam with variable beam characteristics without the need to use free space optics to change the beam characteristics. The VBC fiber 100 includes a first length of optical fiber 104 and a second length of optical fiber 108. The first length of optical fiber 104 and the second length of optical fiber 108 can be the same or different optical fibers and can have the same or different RIPs. The first length of optical fiber 104 and the second length of optical fiber 108 can be connected together by a connector. The first length of optical fiber 104 and the second length of optical fiber 108 can be coupled in other ways, can be spaced apart, or can be connected via an intervening component, such as another length of optical fiber, free space optics, glue, refractive index matching material, etc., or any combination thereof.

[0081] The disturbance device 110 is disposed near and / or surrounds the disturbance zone 106. The disturbance device 110 may be a device, a component, an intra-fiber structure, and / or other features. The disturbance device 110 disturbs at least the light beam 102 in the first length of optical fiber 104 or the second length of optical fiber 108 or a combination thereof to adjust one or more beam characteristics of the light beam 102. In response to the disturbance of the disturbance device 110, the adjustment of the light beam 102 may occur in the first length of optical fiber 104 or the second length of optical fiber 108 or a combination thereof. The disturbance zone 106 may extend over various widths and may or may not extend into a portion of the second length of optical fiber 108. When the light beam 102 propagates in the VBC fiber 100, the disturbance device 110 may physically act on the VBC fiber 100 to disturb the fiber and adjust the characteristics of the light beam 102. Alternatively, the disturbance device 110 may act directly on the light beam 102 to change its beam characteristics. After adjustment, the disturbed optical beam 112 has a different beam characteristic from the beam characteristic of the optical beam 102, which will be fully or partially maintained in the second length optical fiber 108. In another example, the perturbation device 110 does not need to be arranged near the joint. In addition, no joint is required at all, for example, the VBC optical fiber 100 can be a single optical fiber, and the first length optical fiber and the second length optical fiber can be spaced apart or fixed with a small gap (air spaced or filled with optical materials, such as optical glue or refractive index matching material).

[0082] The disturbed light beam 112 is launched into the second length of optical fiber 108, wherein the characteristics of the disturbed light beam 112 are largely maintained or continue to develop as the disturbed light beam 112 propagates, thereby producing an adjusted beam characteristic at the output end of the second length of optical fiber 108. In one example, the new beam characteristic may include an adjusted intensity distribution. In one example, the changed beam intensity distribution will be maintained in various structurally bounded confinement areas of the second length of optical fiber 108. Therefore, the beam intensity distribution can be adjusted to a desired beam intensity distribution optimized for a specific laser processing task. Generally, the intensity distribution of the disturbed light beam 112 will develop as it propagates in the second length of optical fiber 108 to fill the confinement area into which the disturbed light beam 112 is launched in response to the conditions in the first length of optical fiber 104 and the disturbance caused by the disturbance device 110. In addition, depending on the launch conditions and the fiber characteristics, the angular distribution may evolve as the light beam propagates in the second optical fiber. Typically, the fiber largely maintains the input divergence profile, but if the input divergence profile is narrow and / or if the fiber has irregularities or intentional features that perturb the divergence profile, the profile may be widened. Various confinement regions, perturbations, and fiber features of the second length of fiber 108 are described in more detail below. Beams 102 and 112 are conceptual abstractions intended to illustrate how beams propagate through VBC fiber 100 to provide variable beam characteristics and are not intended to accurately simulate the behavior of a particular beam.

[0083] The VBC fiber 100 may be manufactured by a variety of methods, including PCVD (plasma chemical vapor deposition), OVD (outside vapor deposition), VAD (vapor axial deposition), MOCVD (metal-organic chemical vapor deposition), and / or DND (direct nanoparticle deposition). The VBC fiber 100 may include a variety of materials. For example, the VBC fiber 100 may include SiO2, SiO2 doped with GeO2, germanosilicate, phosphorus pentoxide, phosphosilicate, Al2O3, aluminosilicate, or the like, or any combination thereof. The confinement region may be defined by a cladding doped with fluorine, boron, or the like, or any combination thereof. Other dopants may be added to the active fiber, including rare earth ions, for example, Er. 3+ (Erbium), Yb 3+ (Ytterbium), Nd 3+ (Nd), Tm 3+ (Thulium), Ho 3+ (holmium), etc. or any combination thereof. The confinement region may be defined by a cladding having a refractive index lower than the refractive index of the confinement region doped with fluorine or boron. Alternatively, the VBC fiber 100 may include a photonic crystal fiber or a microstructured fiber.

[0084] The VBC fiber 100 is suitable for use with any of a variety of optical fibers, fiber optics, or fiber laser devices, including continuous wave and pulsed fiber lasers, disk lasers, solid state lasers, or diode lasers (with pulse rates not limited except by physical limitations). Furthermore, implementations in planar waveguides or other types of waveguides (not just optical fibers) are within the scope of the claimed technology.

[0085] Figure 2 A cross-sectional view of an exemplary VBC fiber 200 for adjusting beam characteristics of an optical beam is depicted. In one example, the VBC fiber 200 can be a processing fiber in that the optical beam can be delivered to a processing head for material processing. The VBC fiber 200 includes a first length of optical fiber 204 spliced ​​to a second length of optical fiber 208 at a junction 206. A disturbance component 210 is disposed near the junction 206. The disturbance component 210 can be any of a variety of devices configured to be able to adjust the beam characteristics of the optical beam 202 propagating in the VBC fiber 200. In one example, the disturbance component 210 can be a mandrel and / or another device that can provide a means of changing the bend radius and / or bend length of the VBC fiber 200 near the joint. This will be discussed below with reference to FIG. Fig.24 Other examples of perturbation devices are discussed.

[0086] In one example, a first length of optical fiber 204 has a parabolic refractive index RIP 212, as shown in the left RIP diagram. When the optical fiber 204 is straight or nearly straight, most of the intensity distribution of the light beam 202 is concentrated in the center of the optical fiber 204. The second length of optical fiber 208 is a confined optical fiber with RIP 214, as shown in the right RIP diagram. The second length of optical fiber 208 includes confined regions 216, 218, and 220. The confined region 216 is a central core surrounded by two annular (or ring-shaped) confined regions 218 and 220. Layers 222 and 224 are structural barriers composed of low refractive index materials between the confined regions (216, 218, and 220), which are generally referred to as "cladding" regions. In one example, layers 222 and 224 may include fluorosilicate rings; in some embodiments, the fluorosilicate cladding is relatively thin. Other materials may also be used, and the claimed subject matter is not limited thereto.

[0087] In one example, as the light beam 202 propagates along the VBC fiber 200, the perturbation component 210 can physically act on the optical fiber 204 and / or the light beam 202 to adjust its beam characteristics and generate an adjusted light beam 226. In the current example, the intensity distribution of the light beam 202 is modified by the perturbation component 210. After adjusting the light beam 202, the intensity distribution of the adjusted light beam 226 can be concentrated in the outer confinement regions 218 and 220, wherein the intensity is relatively small in the central confinement region 216. Because each of the confinement regions 216, 218 and / or 220 is isolated by a thin layer of lower refractive index material in the barrier layers 222 and 224, the second length of optical fiber 208 can substantially maintain the adjusted intensity distribution of the adjusted light beam 226. The adjusted light beam 226 will generally be distributed in an azimuth within a given confinement region (see, e.g., Figure 7B , 8B , 9B and 10B), but does not (significantly) transition between confinement regions when propagating along the second length of optical fiber 208. Therefore, the adjusted beam characteristics of the adjusted beam 226 are largely maintained within the isolated confinement regions 216, 218 and / or 220.

[0088] In one example, the core confinement region 216 and the annular confinement regions 218 and 220 can be composed of fused silica glass, and the claddings 222 and 224 defining the confinement regions can be composed of fluorosilicate glass. Other materials can be used to form the various confinement regions (216, 218, and 220), including germanosilicates, phosphosilicates, aluminosilicates, etc., or combinations thereof, and the claimed subject matter is not limited thereto. Other materials can be used to form the barrier rings (222 and 224), including fused silica, borosilicates, etc., or combinations thereof, and the claimed subject matter is not limited thereto. In other embodiments, the optical fiber or waveguide includes or consists of various polymers or plastics or crystalline materials. Typically, the refractive index of the core confinement region is greater than the refractive index of the adjacent barrier / cladding region.

[0089] In some examples, it may be desirable to increase the number of confinement regions in the second length of optical fiber to increase the granularity of beam control over beam displacement to fine tune the beam profile. For example, the confinement regions may be configured to provide a stepwise beam displacement.

[0090] Figure 3An exemplary method of perturbing an optical fiber 200 to provide variable beam characteristics of an optical beam is shown. Changing the bend radius of the optical fiber can change the radial beam position, divergence angle, and / or radiance profile of the optical beam within the optical fiber. The bend radius of the VBC optical fiber 200 can be reduced from a first bend radius R1 to a second bend radius R2 around a splice node 206 by using a stepped mandrel or cone as a perturbation component 210. In addition or alternatively, the splice length on the mandrel or cone can be varied. Roller 250 can be used to splice the VBC optical fiber 200 across the perturbation component 210. In one example, the amount of splicing of the roller 250 with the optical fiber 200 has been shown to shift the distribution of the intensity profile to the outer confinement regions 218 and 220 of the optical fiber 200 having a fixed mandrel radius. There are a variety of other methods for changing the bend radius of the optical fiber 200, for example, using a clamping assembly, a flexible tube, etc., or a combination thereof, and the subject matter claimed is not limited thereto. In another example, for a specific bend radius, the length of the VBC optical fiber 200 bend can also change the beam characteristics in a controllable and reproducible manner. In examples, changing the bend radius and / or length (the length over which the optical fiber is bent at a particular bend radius) also modifies the intensity distribution of the optical beam such that one or more modes may be radially offset from the center of the optical fiber core.

[0091] Maintaining the bend radius of the optical fiber at the junction 206 ensures that the adjusted beam characteristics (e.g., radial beam position and radiance profile of the optical beam 202) do not return to their undisturbed states before being launched into the second length of optical fiber 208. In addition, the adjusted radial beam characteristics of the adjusted optical beam 226, including position, divergence angle, and / or intensity distribution, may be changed based on the extent of the reduction in the bend radius and / or the range of the bend length of the VBC fiber 200. Thus, specific beam characteristics may be obtained using this approach.

[0092] In the current example, a first length of optical fiber 204 having a first RIP 212 is spliced ​​at a junction 206 to a second length of optical fiber 208 having a second RIP 214. However, a single optical fiber having a single RIP formed to perturb (e.g., by microbending) the beam characteristics of the beam 202 and to maintain the regulated beam may be used. Such a RIP may be similar to Fig.17 , 18 and / or the RIP shown in the optical fiber shown in 19.

[0093] Figure 4 is the lowest order mode (LP) of the first length of optical fiber 204 showing different fiber bend radii 402. 01), where the perturbation component 210 involves bending the VBC fiber 200. As the fiber bend radius decreases, the light beam propagating in the VBC fiber 200 is adjusted so that the mode is radially offset from the center 404 of the core of the VBC fiber 200 (r=0 microns) towards the core / cladding interface (located at r=100 microns in this example). The higher order modes (LP In ) also shifts with bending. Therefore, for straight or nearly straight fiber (very large bend radius), LP 01 The curve 406 of FIG. 4 is centered at or near the center of the VBC fiber 200. At a bend radius of approximately 6 cm, the LP 01 The curve 408 of LP is offset from the center 406 of the VBC fiber 200 to a radial position of about 40 μm. At a bend radius of about 5 cm, 01 The curve 410 of the VBC fiber 200 is offset from the center 406 to a radial position of about 50 μm. At a bend radius of about 4 cm, the LP 01 The curve 412 of the VBC fiber 200 is offset from the center 406 to a radial position of about 60 μm. At a bend radius of about 3 cm, the LP 01 The curve 414 of the VBC fiber 200 is offset from the center 406 to a radial position of about 80 μm. At a bend radius of about 2.5 cm, the LP 01 The curve 416 of VBC fiber 200 is offset from the center 406 to a radial position of approximately 85 μm. Note that the shape of the mode remains relatively constant (until approaching the edge of the core), which is a specific property of a parabolic RIP. Although this property may be desirable in some circumstances, it is not required for VBC function and other RIPs may be used.

[0094] In one example, if the VBC fiber 200 is straightened, the LP 01 The mode will shift back to the center of the fiber. Thus, the purpose of the second length of fiber 208 is to "trap" or confine the adjusted intensity profile of the beam into a confinement region offset from the center of the VBC fiber 200. The joint between fibers 204 and 208 is included in the bend region, so the shifted mode profile will be preferentially emitted into one of the annular confinement regions 218 and 220, or distributed within the confinement region. Figure 5 and 6 shows this effect.

[0095] First, in Figure 5 and 6In the second length of optical fiber 208 shown in the example of FIG. 1 , confinement region 216 has a diameter of 100 microns, confinement region 218 has a diameter between 120 microns and 200 microns, and confinement region 220 has a diameter between 220 microns and 300 microns. Confinement regions 216, 218, and 220 are separated by 10 μm thick fluorosilicate rings, thereby providing a NA of 0.22 for the confinement regions. Other inner and outer diameters of confinement regions, thicknesses of rings separating confinement regions, NA values ​​of confinement regions, and numbers of confinement regions may be used.

[0096] Using the example dimensions above, Figure 5 FIG. 2 shows a simulated example of a two-dimensional intensity distribution at a node 206 within a second length of optical fiber 208 when the VBC optical fiber 200 is nearly straight. 01 and LP In Within confinement region 216 of optical fiber 208. When VBC optical fiber 200 is straight (e.g., undisturbed), approximately 90% of the power is contained within central confinement region 216, and approximately 100% of the power is contained within confinement regions 216 and 218. Conversely, Figure 6 FIG. 2 is a simulated example of a two-dimensional intensity distribution of a conditioned light beam 226 applied to a node 206 within a second length of optical fiber 208 when the VBC fiber 200 is bent. In response to the VBC fiber 200 being bent at a radius selected to preferentially excite the confinement region 220 (the outermost confinement region) of the second length of optical fiber 208, a majority of the LP 01 and LP In within confinement region 220 of fiber 208. Thus, when fiber 200 is bent to preferentially excite second annular confinement region 220, approximately 75% of the power is contained within confinement region 220 and over 95% of the power is contained within confinement regions 218 and 220. These calculations include LP 01 and two higher order modes, which are typical in some 2-4 kW fiber lasers. For the purposes of these calculations, specific RIPs, sizes, and shapes of the confinement regions of the two fibers were assumed, but other RIPs, sizes, and shapes are possible and claimed subject matter is not limited thereto.

[0097] from Figure 5 and Figure 6It can be clearly seen that, in the case where the perturbation component 210 acts on the VBC fiber 200 to bend the fiber, the state of the bend radius establishes a spatial overlap of the modal intensity distribution of the first length of fiber 204 with the different confinement regions (216, 218 and 220) of the second length of fiber 208. Therefore, changing the bend radius can change the intensity distribution at the output end of the second length of fiber 208, thereby changing the diameter, spot size or intensity profile of the beam, and thus changing its radiance and BPP value. This adjustment of the spot size can be achieved in an all-fiber structure, so that no free-space optics are involved, and therefore the disadvantages of free-space optics described above can be reduced or eliminated. This adjustment can also be performed by other perturbation components that change the bend radius, bend length, fiber tension, temperature, microbends, or other perturbations discussed below.

[0098] In a typical material processing system (e.g., a cutting or welding tool), the output of the processing fiber is imaged by a processing head at or near the workpiece. Figure 5 and 6 The intensity distribution shown enables the beam profile at the workpiece to be changed in order to adjust and / or optimize the process as required. Fig. 7A , 8A , 9A and 10A show end views of a second length of optical fiber 208 at a junction 206 when different, gradually increasing amounts of perturbation are applied to the VBC optical fiber 200 in response to a perturbation assembly 210 acting on the VBC optical fiber 200 to bend the optical fiber at various radii (i.e., the bend radius is reduced). In these predicted examples, a beam from a laser source may be launched into an input optical fiber (not shown) having a core diameter of 40 microns. The input optical fiber will be spliced ​​to the first length of optical fiber 204. However, the specific implementation details will vary depending on the application details. Specifically, the spatial profile and divergence distribution of the output beam and its dependence on the bend radius (or other state of applied perturbation) will depend on the specific RIP employed, the splicing parameters, and the characteristics of the laser source launched into the first optical fiber.

[0099] Whether or not adjusted, the beam 202 has an intensity distribution in which a region thereof spatially overlaps one or more confinement regions. Selectable perturbation states may be applied to appropriately shift the beam 202, change its BPP, or modify other beam characteristics (i.e., changes in how the aforementioned regions spatially overlap one or more confinement regions) in order to generate an adjusted beam 226. Thus, different beam shapes may be generated based on the amount of perturbation applied to the VBC fiber 200.

[0100] Fig. 7ASchematic diagram of the input end of optical fiber 208 (the end coupled to the output end of the first optical fiber at the splice junction 206). Optical fiber 208 is shown receiving light beam 202 in its central coaxial confinement region 216, where light beam 202 is generally undisturbed, thereby generating therefrom at the output end of optical fiber 208 as shown in FIG. Figure 7B The Gaussian intensity distribution shown has Figure 7C The corresponding Gaussian intensity profile 720 is shown. For example, when the VBC fiber 200 is straight, Fig. 7A The approximately Gaussian input beam shown is substantially confined in the confinement region 216 to generate the desired Gaussian intensity distribution at the output. The initial, nominally undisturbed state maintains a substantially Gaussian intensity profile with approximately 90% of its power contained within the central confinement region 216, while incremental changes in state can transform the substantially Gaussian distribution from a low-order to a high-order substantially super-Gaussian distribution. Different perturbation states can be used to change the Gaussian center, RMS width, or other Gaussian distribution parameters of the Gaussian intensity profile 720, or to generate a super-Gaussian beam within the central confinement region 216.

[0101] Although multiple portions of the confinement region are excited from one side at the splice node 206, due to the scrambling of the light beam within the confinement region as it propagates within the VBC fiber 200, the light beam on the opposite side (at Figure 7B , 8B The resulting intensity distribution (shown at the output in , 9B and 10B) is nearly symmetrical in azimuth. Although the beam is typically scrambled in azimuth as it propagates, various structures or perturbations (e.g., coils) can be included to facilitate this process.

[0102] In some embodiments, it may be desirable to divide the optical power of the adjusted beam 226 between the confinement regions 216, 218, and / or 220 rather than concentrating it in a single region. In other words, a particular confinement region does not need to be specifically excited. For example, as the bend radius decreases, the intensity distribution at the input end shifts to confinement regions 218 and 220 of larger diameter that are farther from confinement region 216, e.g., see Fig. 8A , 9A and 10A, this offset is visible, and the resulting outputs are shown in Figure 8B , 9B and 10B. The ability to distribute intensity over one or more confined regions based on the amount of perturbation advantageously facilitates material processing applications that are optimized by having a flatter (or distributed) beam intensity profile. Using different fiber RIPs to achieve this feature may also enable other applications where more discrete excitation of specific confined regions is desired.

[0103] Fig. 8A218. The intensity distribution is depicted when the bend radius of the VBC fiber 200 is selected to change the intensity distribution between the confinement regions 216 and 218. In one example, the selected amount of perturbation applied is an amount that simultaneously shifts and expands the beam 202 when forming the adjusted beam 226 so that a region of its intensity distribution spatially overlaps with an adjacent confinement region. Thus, the input end of the optical fiber 208 receives the adjusted beam 226 at its central coaxial confinement region 216 and adjacent portions of the intermediate confinement region 218 (e.g., adjacent portions optionally separated by a low refractive index cladding), thereby producing a beam having Figure 8B The output beam has a substantially super-Gaussian intensity distribution, which has Figure 8C The corresponding super-Gaussian intensity profile 820 is shown.

[0104] In some embodiments, the above-described shifting and expansion of the light beam 202 results in the adjusted light beam 226 having a non-zero ellipticity (this phenomenon is also modeled as Figure 6 826), which contributes to a more uniform intensity distribution over the confined area, resulting in a relatively flat top of a higher order super Gaussian intensity profile 824. Conversely, a smaller perturbation can be employed to generate a lower order super Gaussian intensity profile 826. In some embodiments, a low order super Gaussian intensity profile 826 is formed by applying a smaller perturbation so as to concentrate more intensity in the central coaxial confined area. Conversely, it should be readily appreciated that a high order super Gaussian intensity profile 824 can approach a flat top (i.e., a top hat for a circular beam) intensity profile 830.

[0105] The skilled person will appreciate that the higher the order of the super-Gaussian profile, the steeper its corners, as one eventually approaches an ideal flat top. However, in practice, a flat top profile retains at least some rounding at its corners, and is typically approximated by a high-order super-Gaussian profile, rather than a strictly rectangular profile. Thus, a super-Gaussian beam profile with a substantially flat top and Gaussian falloff is more generally represented by the following equation:

[0106]

[0107] Where n is the order, r is the radial position, l p is the peak intensity (on the beam axis) of a Gaussian beam with Gaussian beam radius w

[0108] and Fig. 8A Compared to the example, Fig. 9AThe example of shows a larger radial offset and smaller ellipticity, thereby placing more intensity away from region 216 and into region 218. As with the previous example, the optimal offset or ellipticity can be determined empirically based on the specific application. For some applications, the bend radius can be further reduced and selected to shift the intensity distribution further outward into restricted regions 218 and 220, leaving less power density in the center, thereby approximating at the output as Fig. 9B The saddle-shaped distribution shown has Fig. 9C The corresponding saddle-shaped intensity profile 920 is shown. Profile 920 is generally defined by a bimodal shape that includes two local maxima 930 and a local minimum 940 therebetween. In some embodiments, the local minimum may reach approximately zero intensity (which would be referred to as a "donkey" beam), while other embodiments maintain the remaining intensity at the local minimum.

[0109] Fig. 10A Another schematic diagram of the input end of the optical fiber 208 is shown, which mainly receives the conditioned light beam 226 in its outer coaxial confinement region 220 so as to produce a light beam having Fig. 10B The so-called annular mode beam shown has Fig. 10C The corresponding intensity profile 1020 is shown. In contrast to the previous example, the adjusted beam 226 also has a smaller diameter in order to concentrate the intensity in the outer coaxial confinement region 220. For example, using Figure 7B , 8B The smaller diameter is achieved by using a RIP for the first optical fiber that is different from the RIP used in the previous example shown in 9B.

[0110] The skilled person will understand that Figure 7C , 8C The idealized graphs in , 9C and 10C show a smooth transition. In reality, however, the cladding between confinement regions results in slight discontinuities in intensity. However, these discontinuities are not important in fundamentally changing the properties of the selected beam shape. In other words, for example, a saddle shape need not have a completely smooth dual-mode profile to still serve its intended purpose.

[0111] You can use different Figure 2 Parameters of the fibers shown and still remain within the scope of the claimed subject matter. Specifically, different RIPs and core sizes and shapes can be used to facilitate compatibility with different input beam profiles and achieve different output beam characteristics. Figure 2In addition to the parabolic refractive index profile shown, example RIPs for the first length of optical fiber include other gradient refractive index profiles, step refractive indices, pedestal designs (i.e., nested cores with gradually decreasing refractive index as the distance from the center of the fiber increases), and designs with nested cores having the same refractive index value but with different NA values ​​for the central core and surrounding annulus. Figure 2 In addition to the outlines shown, example RIPs for the second length of optical fiber include confined optical fibers having different numbers of confined regions, non-uniform confined region thicknesses, different and / or non-uniform values ​​for the thickness of the ring surrounding the confined region, different and / or non-uniform NA values ​​for the confined regions, different refractive index values ​​for the high and low index portions of the RIP, non-circular confined regions (e.g., elliptical, oval, polygonal, square, rectangular, or combinations thereof), and other designs, such as in Figure 26-28 . In addition, the VBC fiber 200 and other examples of VBC fibers described herein are not limited to the use of two optical fibers. In some examples, implementations may include the use of one optical fiber or more than two optical fibers. In some cases, the optical fiber may not be axially uniform; for example, a fiber Bragg grating or a long period grating may be included, or the diameter may vary along the length of the optical fiber. In addition, the optical fiber does not have to be azimuthally symmetric, for example, the core may have a square or polygonal shape. Various optical fiber coatings (buffer layers) may be used, including high refractive index or refractive index matching coatings (which strip light at the glass-polymer interface) and low refractive index coatings (which guide light by total internal reflection at the glass-polymer interface). In some examples, multiple optical fiber coatings may be used on the VBC fiber 200.

[0112] Figure 11-16 A cross-sectional view of an example of a first length of optical fiber capable of adjusting beam characteristics in a VBC fiber in response to a perturbation of a beam propagating in the first length of optical fiber is shown. Some examples of beam characteristics that can be adjusted in the first length of optical fiber are: beam diameter, beam divergence profile, BPP, intensity profile, brightness, M 2 factor, NA, light intensity distribution, power density distribution, radial beam position, radiance, spot size, etc. or any combination thereof. Figure 11-16 The first lengths of optical fiber depicted in and described below are merely examples and do not provide an exhaustive description of the variety of first lengths of optical fiber that may be used to adjust beam characteristics in a VBC fiber optic assembly. Figure 11-16 The selection of the material of the first length of optical fiber shown, the suitable RIP and other variables depends at least on the desired beam output. Various optical fiber variables are considered and are within the scope of the claimed subject matter. Therefore, the claimed subject matter is not limited by the examples provided herein.

[0113] exist Fig.11, a first length of optical fiber 1100 includes a step-index refractive profile 1102. Fig.12 A first length of optical fiber 1200 is shown, comprising a "pedestal RIP" (ie, a core comprising a step-index region surrounded by a larger step-index region) 1202. Fig.13 A first length of optical fiber 1300 including a multi-pedestal RIP 1302 is shown.

[0114] Fig.14A A first length of optical fiber 1400 is shown, including a gradient index profile 1418 surrounded by a down-doped region 1404. When the optical fiber 1400 is perturbed, the modes may move radially outward in the optical fiber 1400 (e.g., during bending of the optical fiber 1400). The gradient index profile 1402 can be designed to facilitate maintaining or even compressing the mode shape. Such a design can facilitate adjusting a beam propagating in the optical fiber 1400 to generate a beam having a beam intensity distribution concentrated at the periphery of the optical fiber (i.e., in a portion of the optical fiber core that is offset from the optical fiber axis). As described above, when the adjusted beam is coupled into a second length of optical fiber having a confinement region, the intensity distribution of the adjusted beam can be confined to the outermost confinement region, thereby providing an annular intensity distribution. A beam spot having a narrow outer confinement region can be used to achieve certain material processing actions.

[0115] Fig. 14B A first length of optical fiber 1406 is shown, including a gradient refractive index profile 1414 surrounded by a down-doped region 1408, similar to the gradient refractive index profile of optical fiber 1400. However, optical fiber 1406 includes a diverging structure 1410 (low refractive index region), as shown in profile 1412. The diverging structure 1410 is a region formed by a material having a lower refractive index than the surrounding core. When a light beam is launched into the first length of optical fiber 1406, refraction from the diverging structure 1410 causes the light beam divergence to increase in the first length of optical fiber 1406. The amount of increase in divergence depends on the amount of spatial overlap of the light beam with the diverging structure 1410 and the size of the refractive index difference between the diverging structure 1410 and the core material. The diverging structure 1410 can have a variety of shapes, depending on the input divergence profile and the desired output divergence profile. In one example, the diverging structure 1410 has a triangular or gradient refractive index shape.

[0116] Fig.15A first length of optical fiber 1500 is shown, including a parabolic refractive index central region 1502 surrounded by a constant refractive index region 1504. A low-index annular layer (or low-index ring or ring) 1506 surrounding the parabolic refractive index central region 1502 is between the constant refractive index region 1504 and the parabolic refractive index central region 1502. The low-index ring 1506 helps guide a light beam propagating in the optical fiber 1500. When the propagating light beam is disturbed, the modes move radially outward in the optical fiber 1500 (e.g., during bending of the optical fiber 1500). The parabolic refractive index region 1502 facilitates maintaining the mode shape as one or more modes move radially outward. When the modes reach the constant refractive index region 1504 at the outer portion of the RIP 1510, they will be compressed on the low-index ring 1506, which (compared to the Fig.14A and 14B The first fiber RIP 1510 may result in preferential excitation of the outermost confinement region of the second fiber compared to the first fiber RIP shown. In one implementation, this fiber design works with a confinement fiber having a central step-index core and a single annular core. The parabolic refractive index portion 1502 of the RIP 1510 overlaps the central step-index core of the confinement fiber. The constant refractive index portion 1504 overlaps the annular core of the confinement fiber. The constant refractive index portion 1504 of the first fiber is intended to make it easier for the light beam to move to overlap with the annular core by bending. This fiber design is also applicable to other designs of confinement fibers.

[0117] Fig.16 A first length of optical fiber 1600 is shown, including guiding regions 1604, 1606, 1608, and 1616 defined by lower index layers 1610, 1612, and 1614, wherein the refractive indices of lower index layers 1610, 1612, and 1614 are stepped, or more generally, do not all have the same value. Figure 2 ) acts on the optical fiber 1600, the step index layer can be used to confine the beam intensity to certain guiding regions (1604, 1606, 1608, and 1616). In this way, the adjusted beam can be captured in the guiding region through a series of perturbation actions (e.g., through a series of bend radii, a series of bend lengths, a series of microbending pressures, and / or a series of acousto-optic signals), thereby allowing a certain degree of perturbation tolerance before the beam intensity distribution moves to a farther radial position in the optical fiber 1600. Therefore, the change of beam characteristics can be controlled step by step. The radial width of the guiding regions 1604, 1606, 1608, and 1616 can be adjusted to obtain the desired ring width, which may be required by the application. In addition, if desired, the guiding region can have a thicker radial width to facilitate capturing a larger portion of the incident beam profile. Region 1606 is an example of such a design.

[0118] Figure 17-21 Examples of optical fibers configured to maintain and / or limit adjusted beam characteristics in a second length of optical fiber (e.g., optical fiber 208) are depicted. These optical fiber designs are referred to as "ring-limited fibers" because they include a central core surrounded by a ring or annular core. These designs are merely examples and are not an exhaustive description of the various optical fiber RIPs that can be used to maintain and / or limit adjusted beam characteristics within an optical fiber. Accordingly, the claimed subject matter is not limited to the examples provided herein. Furthermore, the above Figure 11-16 Any first length of optical fiber described in Figure 17-21 Any second length optical fiber combination described.

[0119] Fig.17 A cross-sectional view of an exemplary second length of optical fiber for maintaining and / or limiting adjusted beam characteristics in a VBC fiber assembly is shown. When a disturbed beam is coupled from a first length of optical fiber to a second length of optical fiber 1700, the second length of optical fiber 1700 can maintain at least a portion of the beam characteristics adjusted in response to the disturbance in the first length of optical fiber within one or more confinement regions 1704, 1706, and / or 1708. Optical fiber 1700 has a RIP 1702. Each of the confinement regions 1704, 1706, and / or 1708 is bounded by a lower refractive index layer 1710 and / or 1712. This design enables the second length of optical fiber 1700 to maintain adjusted beam characteristics. As a result, the beam output by optical fiber 1700 will substantially maintain the received adjusted beam, as modified in the first length of optical fiber, thereby providing the output beam with adjusted beam characteristics, which can be customized according to the processing task or other application.

[0120] Similarly, Fig.18 A cross-sectional view of an exemplary second length of optical fiber 1800 is depicted for maintaining and / or limiting the adjusted beam characteristics in response to a perturbation of a first length of optical fiber in a VBC optical fiber assembly. Optical fiber 1800 has a RIP 1802. However, the confinement regions 1808, 1810, and / or 1812 have a thickness that is different from the thickness of confinement regions 1704, 1706, and 1708. Each of confinement regions 1808, 1810, and / or 1812 is bounded by a lower refractive index layer 1804 and / or 1806. Varying the thickness of the confinement regions (and / or barrier regions) enables the confined adjusted radiance profile to be customized or optimized by selecting a specific radial location at which the adjusted beam is confined.

[0121] Fig.19A cross-sectional view of an exemplary second length of optical fiber 1900 having a RIP 1902 is depicted for maintaining and / or confining an adjusted beam configured to provide variable beam characteristics in a VBC optical fiber assembly. In this example, the number and thickness of confinement regions 1904, 1906, 1908, and 1910 are different from the number and thickness of optical fibers 1700 and 1800, and barrier layers 1912, 1914, and 1916 also have different thicknesses. In addition, confinement regions 1904, 1906, 1908, and 1910 have different refractive indices, and barrier layers 1912, 1914, and 1916 also have different refractive indices. This design can further enable more refined or optimized customization of confining and / or maintaining the radiation of an adjusted beam for a specific radial position within the optical fiber 1900. When the disturbed light beam is emitted from the first length of optical fiber to the second length of optical fiber 1900, the modified beam characteristics of the light beam (having an adjusted intensity distribution, radial position and / or divergence angle, etc. or a combination thereof) are confined to a specific radius by one or more confinement regions 1904, 1906, 1908 and / or 1910 of the second length of optical fiber 1900.

[0122] As previously described, the divergence angle of the light beam can be maintained or adjusted and then maintained in the second length of optical fiber. There are a variety of ways to change the divergence angle of the light beam. The following are examples of optical fibers that are configured to be able to adjust the divergence angle of a light beam that propagates from a first length of optical fiber to a second length of optical fiber in an optical fiber assembly to change the characteristics of the light beam. However, these are merely examples and are not an exhaustive description of the various methods that can be used to adjust the divergence of the light beam. Therefore, the claimed subject matter is not limited to the examples provided herein.

[0123] Fig. 20A cross-sectional view of an exemplary second length of optical fiber 2000 having a RIP 2002 is depicted for modifying, maintaining and / or limiting beam characteristics adjusted in response to a disturbance of the first length of optical fiber. In this example, the second length of optical fiber 2000 is similar to the second length of optical fiber described previously and forms part of a VBC optical fiber assembly for delivering variable beam characteristics, as described above. There are three confinement regions 2004, 2006 and 2008 and three barrier layers 2010, 2012 and 2016. The second length of optical fiber 2000 also has a divergent structure 2014 located within the confinement region 2006. The divergent structure 2014 is a region formed of a material having a lower refractive index than the surrounding confinement region. When a beam of light is launched into the second length of optical fiber 2000, refraction from the divergent structure 2014 causes the divergence of the beam of light to increase in the second length of optical fiber 2000. The amount of increase in divergence depends on the amount of spatial overlap of the beam with the divergent structure 2014 and the magnitude of the refractive index difference between the divergent structure 2014 and the core material. By adjusting the radial position of the beam near the launch point into the second length of optical fiber 2000, the divergence profile can be changed. The adjusted divergence of the beam is maintained in the optical fiber 2000, which is configured to transmit the adjusted beam to a processing head, another optical system (e.g., a fiber-to-fiber coupler or a fiber-to-fiber switch), a workpiece, etc., or a combination thereof. In one example, the divergence structure 2014 can have a radial position of about 10° relative to the surrounding material. -5 -3x10 -2 Other values ​​of the refractive index drop may be used within the scope of the present disclosure, and the claimed subject matter is not limited thereto.

[0124] Fig.21 A cross-sectional view of an exemplary second length optical fiber 2100 having a RIP 2102 is depicted for modifying, maintaining and / or limiting the characteristics of a beam adjusted in response to a disturbance of the first length optical fiber. The second length optical fiber 2100 forms part of a VBC optical fiber assembly for transmitting a beam with variable characteristics. In this example, there are three restriction regions 2104, 2106 and 2108 and three barrier layers 2110, 2112 and 2116. The second length optical fiber 2100 also has a plurality of divergent structures 2114 and 2118. The divergent structures 2114 and 2118 are regions formed of a gradient low refractive index material. When the light beam is emitted from the first length optical fiber to the second length optical fiber 2100, the refraction from the divergent structures 2114 and 2118 causes the divergence of the light beam to increase. The amount of increase in divergence depends on the amount of spatial overlap of the light beam with the diverging structures and the magnitude of the refractive index difference between the diverging structures 2114 and / or 2118 and the surrounding core material of the confinement regions 2106 and 2104, respectively. By adjusting the radial position of the light beam near the launch point into the second length of optical fiber 2100, the divergence profile can be altered. Fig.21 The design shown allows the intensity profile and the divergence profile to be varied somewhat independently by selecting a particular confinement region and the divergence profile within the confinement region (because each confinement region can include a divergence structure). The adjusted divergence of the light beam is maintained in the optical fiber 2100, which is configured to transmit the adjusted light beam to a processing head, another optical system, or a workpiece. The divergence structures 2114 and 2118 formed with a gradient or non-constant refractive index enable adjustment of the divergence profile of the light beam propagating in the optical fiber 2100. The adjusted beam characteristics (e.g., radiance profile and / or divergence profile) can be maintained when transmitted to the processing head by the second optical fiber. Alternatively, when the second optical fiber is routed to the processing optical fiber that transmits the light beam to the processing head or the workpiece through a fiber-to-fiber coupler (FFC) and / or a fiber-to-fiber switch (FFS), the adjusted beam characteristics, such as the radiance profile and / or the divergence profile, can be maintained or further adjusted.

[0125] Figure 26-28 is a cross-sectional view illustrating examples of optical fibers and optical fiber RIPs configured to maintain and / or limit adjusted beam characteristics of a light beam propagating in an azimuthally asymmetric second length of optical fiber, wherein the beam characteristics are adjusted in response to a perturbation of a first length of optical fiber coupled to the second length of optical fiber and / or a perturbation of the light beam by a perturbation device 110. These azimuthally asymmetric designs are merely examples and are not an exhaustive description of the various optical fiber RIPs that may be used to maintain and / or limit adjusted beam characteristics within an azimuthally asymmetric optical fiber. Accordingly, the claimed subject matter is not limited to the examples provided herein. Furthermore, any of the various first length optical fibers (e.g., similar to those described above) may be coupled to any azimuthally asymmetric second length optical fiber (e.g., similar to Figure 26-28 those described in ).

[0126] Fig.26 The RIPs at different azimuth angles are shown through a cross section of an elliptical optical fiber 2600. At a first azimuth angle 2602, the optical fiber 2600 has a first RIP 2604. At a second azimuth angle 2606, which is rotated 45° from the first azimuth angle 2602, the optical fiber 2600 has a second RIP 2608. At a third azimuth angle 2610, which is rotated another 45° from the second azimuth angle 2606, the optical fiber 2600 has a third RIP 2612. The first RIP 2604, the second RIP 2608, and the third RIP 2612 are all different.

[0127] Fig. 27The RIPs of different azimuth angles are shown through a cross section of a multi-core optical fiber 2700. At a first azimuth angle 2702, the optical fiber 2700 has a first RIP 2704. At a second azimuth angle 2706, the optical fiber 2700 has a second RIP 2708. The first RIP 2704 and the second RIP 2708 are different. In one example, the perturbation device 110 can act in multiple planes to launch the adjusted light beam into different regions of the azimuthally asymmetric second optical fiber.

[0128] Fig.28 The RIPs at different azimuth angles are shown through a cross section of an optical fiber 2800 having at least one crescent-shaped core. In some cases, the corners of the crescent can be rounded, flattened, or other shapes, which can minimize optical losses. At a first azimuth angle 2802, the optical fiber 2800 has a first RIP 2804. At a second azimuth angle 2806, the optical fiber 2800 has a second RIP 2808. The first RIP 2804 and the second RIP 2808 are different.

[0129] Fig.22A An example of a laser system 2200 including a VBC fiber assembly 2202 is shown, which is configured to provide variable beam characteristics. The VBC fiber assembly 2202 includes a first length of optical fiber 104, a second length of optical fiber 108, and a perturbation device 110. The VBC fiber assembly 2202 is disposed between a feed fiber 2212 (i.e., an output fiber from a laser source) and a VBC delivery fiber 2240. The VBC delivery fiber 2240 may include a second length of optical fiber 108 or an extension of the second length of optical fiber 108 that modifies, maintains, and / or limits the adjusted beam characteristics. The beam 2210 is coupled into the VBC fiber assembly 2202 via the feed fiber 2212. The fiber assembly 2202 is configured to change the characteristics of the beam 2210 according to the various examples described above. The output of the fiber assembly 2202 is an adjusted beam 2214, which is coupled into the VBC delivery fiber 2240. The VBC delivery fiber 2240 delivers the conditioned beam 2214 to the free-space optical assembly 2208, which then couples the beam 2214 into the processing fiber 2204. The conditioned beam 2214 is then delivered by the processing fiber 2204 to the processing head 2206. The processing head may include waveguide optics (e.g., optical fibers and fiber couplers), free-space optics (e.g., lenses, mirrors, filters, diffraction gratings), and / or beam scanning components (e.g., galvanometer scanners, polygon mirror scanners) or other scanning systems for shaping the beam 2214 and delivering the shaped beam to the workpiece.

[0130] In the laser system 2200, one or more free space optics of the assembly 2208 may be arranged in an FFC or other beam coupler 2216 to couple the conditioned beam 2214 (at Fig.22A Various optical operations may be performed on the processing head 2206 (indicated by dashed lines different from the dashed lines of the beam 2210). For example, the free space optical assembly 2208 may maintain the adjusted beam characteristics of the beam 2214. The processing fiber 2204 may have the same RIP as the VBC delivery fiber 2240. Thus, the adjusted beam characteristics of the adjusted beam 2214 may be maintained all the way to the processing head 2206. The processing fiber 2204 may include a RIP similar to any of the second lengths of optical fiber described above, including a restricted region.

[0131] Alternatively, if Fig. 22B As shown, free space optical assembly 2208 can change the adjusted beam characteristics of beam 2214 by, for example, increasing or decreasing the divergence and / or spot size of beam 2214 (e.g., by enlarging or shrinking beam 2214) and / or otherwise further modifying adjusted beam 2214. In addition, processing fiber 2204 can have a different RIP than VBC delivery fiber 2240. Thus, the RIP of processing fiber 2204 can be selected to maintain the additional adjustment of adjusted beam 2214 by the free space optical device of assembly 2208, thereby generating a twice adjusted beam 2224 (at Fig. 22B 2214 is represented by a dotted line different from the dotted line of beam 2214).

[0132] Fig.23 An example of a laser system 2300 is shown, which includes a VBC fiber assembly 2302 disposed between a feeding fiber 2312 and a VBC delivery fiber 2340. During operation, a light beam 2310 is coupled into the VBC fiber assembly 2302 via the feeding fiber 2312. The fiber assembly 2302 includes a first length of optical fiber 104, a second length of optical fiber 108, and a perturbation device 110, and is configured to change the characteristics of the light beam 2310 according to the various examples described above. The fiber assembly 2302 generates an adjusted light beam 2314 output by the VBC delivery fiber 2340. The VBC delivery fiber 2340 includes a second length of optical fiber 108 for modifying, maintaining, and / or limiting the adjusted beam characteristics in the fiber assembly 2302 according to the various examples described above (e.g., see Figure 17-21). The VBC delivery fiber 2340 couples the conditioned beam 2314 into a beam switch (FFS) 2332, which then couples its various output beams to one or more of a plurality of processing fibers 2304, 2320, and 2322. The processing fibers 2304, 2320, and 2322 deliver the conditioned beams 2314, 2328, and 2330 to the respective processing heads 2306, 2324, and 2326.

[0133] In one example, the beam switch 2332 includes one or more sets of free-space optics 2308, 2316, and 2318 configured to perform various optical operations on the adjusted beam 2314. The free-space optics 2308, 2316, and 2318 can maintain or change the adjusted beam characteristics of the beam 2314. Therefore, the adjusted beam 2314 can be maintained or further adjusted by the free-space optics. The processing fibers 2304, 2320, and 2322 can have the same or different RIPs as the RIP of the VBC delivery fiber 2340, depending on whether it is desired to maintain or further modify the beams delivered from the free-space optics components 2308, 2316, and 2318 to the corresponding processing fibers 2304, 2320, and 2322. In other examples, one or more beam portions of the beam 2310 are coupled to the workpiece without adjustment, or different beam portions are coupled to the corresponding VBC fiber components, so that beam portions associated with multiple beam characteristics can be provided for simultaneous workpiece processing. Alternatively, beam 2310 can be switched to one or more of a set of VBC fiber optic assemblies.

[0134] Routing the conditioned beam 2314 through any of the free space optical components 2308, 2316, and 2318 enables various additional conditioned beams to be delivered to the processing heads 2206, 2324, and 2326. Thus, the laser system 2300 provides additional degrees of freedom to change the characteristics of the beam and to switch the beam between processing heads ("time sharing") and / or to deliver the beam to multiple processing heads simultaneously ("power sharing").

[0135] For example, the free space optics in the beam switch 2332 can direct the conditioned beam 2314 to a free space optics assembly 2316 that is configured to maintain the conditioned properties of the beam 2314. The processing fiber 2304 can have the same RIP as the RIP of the VBC delivery fiber 2340. Thus, the beam delivered to the processing head 2306 will be the maintained conditioned beam 2314.

[0136] In another example, the beam switch 2332 can direct the conditioned beam 2314 to a free space optical assembly 2318 that is configured to maintain the conditioned characteristics of the conditioned beam 2314. The processing fiber 2320 can have a RIP that is different from the RIP of the VBC delivery fiber 2340 and can be configured in Fig. 20 and 21 The divergence changing structure described in , to provide additional adjustment to the divergence distribution of the beam 2314. Therefore, the beam transmitted to the processing head 2324 will be a twice adjusted beam 2328 having a beam divergence profile different from the beam divergence profile of the adjusted beam 2314.

[0137] Processing optical fibers 2304, 2320, and / or 2322 can include a RIP similar to any of the second lengths of optical fiber described above, including restricted areas or various other RIPs, and claimed subject matter is not limited in this regard.

[0138] In yet another example, the free space optical switch 2332 can direct the adjusted beam 2314 to the free space optical assembly 2308, which is configured to change the beam characteristics of the adjusted beam 2314. The processing fiber 2322 can have a RIP that is different from the RIP of the VBC delivery fiber 2340, and can be configured to maintain (or alternatively further modify) the new, further adjusted characteristics of the beam 2314. Thus, the beam delivered to the processing head 2326 will be a twice adjusted beam 2330 having beam characteristics that are different from the beam characteristics of the adjusted beam 2314 (due to the adjusted divergence profile and / or intensity profile).

[0139] exist Fig.22A , 22B In 23, the optical device in the FFC or FFS can adjust the spatial profile and / or divergence profile by magnifying or reducing the light beam 2214 before launching into the processing fiber. The spatial profile and / or divergence profile can also be adjusted via other optical transformations. The launch position launched into the processing fiber can also be adjusted. These methods can be used alone or in combination.

[0140] Fig.22A , 22B 23 merely provide examples of various combinations of adjustments to beam characteristics using free space optics and fiber RIP to maintain or modify the adjusted beams 2214 and 2314. The examples provided above are not exhaustive and are provided for illustrative purposes only. Therefore, the claimed subject matter is not limited thereto.

[0141] Fig.24Various examples of perturbation devices, assemblies, or methods for perturbing a VBC fiber 200 and / or a light beam propagating in the VBC fiber 200 according to various examples provided herein (collectively referred to herein as "perturbation devices 110" for simplicity) are shown. The perturbation device 110 can be any of a variety of devices, methods, and / or assemblies that are configured to adjust the beam characteristics of a light beam propagating in the VBC fiber 200 in response to the application of one or more different perturbation states. Some examples of various perturbation states that can be applied to the VBC fiber 200 include, but are not limited to, the amount or direction of bending, transverse mechanical stress, mechanical pressure caused by acoustic oscillations, temperature changes, piezoelectric transducer displacement, and a changing period or amplitude of a refractive grating. Changes in one or more states establish different perturbation states. To change one or more of these states, the perturbation device 110 may be a mandrel 2402, a microbend 2404 in a VBC fiber, a flexible tube 2406, an acousto-optic transducer 2408, a thermal device 2410, a piezoelectric device 2412, a grating 2414, a clamp 2416 (or other fastener), etc., or any combination thereof. These are merely examples of perturbation devices 100, and are not an exhaustive list of perturbation devices 100, and the claimed subject matter is not limited thereto.

[0142] The mandrel 2402 can be used to perturb the VBC fiber 200 by providing the VBC fiber 200 with a bendable form. As described above, reducing the bend radius of the VBC fiber 200 will move the intensity distribution of the light beam radially outward. In some examples, the mandrel 2402 can be stepped or conical to provide discrete bend radius levels. Alternatively, the mandrel 2402 can include a taper without steps to provide a continuous bend radius, thereby more precisely controlling the bend radius. The radius of curvature of the mandrel 2402 can be constant (e.g., cylindrical) or non-constant (e.g., elliptical). Similarly, the flexible tube 2406, the clamp 2416 (or other type of fastener), or the roller 250 can be used to guide and control the bending of the VBC fiber 200 around the mandrel 2402. In addition, changing the length of the fiber that is bent at a specific bend radius can also modify the intensity distribution of the light beam. VBC fiber 200 and mandrel 2402 can be configured to predictably change the intensity distribution within the first fiber (e.g., proportional to the length and / or bend radius of the fiber bend). Roller 250 can move up and down along track 2442 on platform 2434 to change the bend radius of VBC fiber 200.

[0143] With or without the mandrel 2402, the clamp 2416 (or other fastener) can be used to guide and control the bend of the VBC fiber 200. The clamp 2416 can move up and down along the track 2442 or platform 2446. The clamp 2416 can also be rotated to change the bend radius, tension, or direction of the VBC fiber 200. The controller 2448 can control the movement of the clamp 2416.

[0144] In another example, the perturbation device 110 can be a flexible tube 2406 and can guide the VBC fiber 200 to bend with or without the mandrel 2402. The flexible tube 2406 can surround the VBC fiber 200. The tube 2406 can be made of a variety of materials and can be manipulated using a piezoelectric transducer controlled by the controller 2444. In another example, a clamp or other fastener can be used to move the flexible tube 2406.

[0145] Microbends 2404 in VBC fiber are localized perturbations caused by lateral mechanical stress on the fiber. Microbends can cause mode coupling and / or transitions from one confinement region to another confinement region within the fiber, resulting in different beam characteristics of a beam propagating in VBC fiber 200. Mechanical stress can be applied by actuator 2436 controlled by controller 2440. However, this is merely one example of a method of inducing mechanical stress in fiber 200, and the claimed subject matter is not limited thereto.

[0146] An acousto-optic transducer (AOT) 2408 can be used to induce disturbances in a light beam propagating in a VBC optical fiber using acoustic waves. The disturbance is caused by the oscillating mechanical pressure of the acoustic wave modifying the refractive index of the optical fiber. The period and intensity of the acoustic wave are related to the frequency and amplitude of the acoustic wave, thereby allowing dynamic control of the acoustic wave disturbance. Therefore, the disturbance component 110 including the AOT 2408 can be configured to change the beam characteristics of the light beam propagating in the optical fiber. In one example, the piezoelectric transducer 2418 can generate the acoustic wave and can be controlled by the controller or driver 2420. The acoustic wave induced in the AOT 2408 can be modulated to change and / or control the beam characteristics of the light beam in the VBC 200 in real time. However, this is merely an example of a method for creating and controlling the AOT 2408, and the subject matter claimed is not limited thereto.

[0147] The thermal device 2410 can be used to induce a disturbance in a light beam propagating in a VBC optical fiber using heat. The disturbance is caused by modifying the RIP of the optical fiber induced by the heat. The disturbance can be dynamically controlled by controlling the amount of heat delivered to the optical fiber and the length to which the heat is applied. Thus, the disturbance assembly 110 including the thermal device 2410 can be configured to change a range of beam characteristics. The thermal device 2410 can be controlled by a controller 2450.

[0148] The piezoelectric transducer 2412 can be used to induce a perturbation of a light beam propagating in a VBC fiber using piezoelectric action. The perturbation is caused by modifying the RIP of the optical fiber induced by the piezoelectric material connected to the optical fiber. The piezoelectric material in the form of a sheath around the bare optical fiber can apply tension or compression to the optical fiber, thereby modifying its refractive index via the resulting density changes. The perturbation can be dynamically controlled by controlling the voltage of the piezoelectric device 2412. Therefore, the perturbation assembly 110 including the piezoelectric transducer 2412 can be configured to change the characteristics of the optical beam within a specific range.

[0149] In one example, the piezoelectric transducer 2412 can be configured to move the VBC fiber 200 in multiple directions (e.g., axially, radially, and / or laterally) based on multiple factors, including how the piezoelectric transducer 2412 is connected to the VBC fiber 200, the polarization direction of the piezoelectric material, the applied voltage, etc. In addition, the VBC fiber 200 can be bent using the piezoelectric transducer 2412. For example, driving a length of piezoelectric material having multiple sections including opposing electrodes can cause the piezoelectric transducer 2412 to bend in a lateral direction. The voltage applied to the piezoelectric transducer 2412 by the electrode 2424 can be controlled by the controller 2422 to control the displacement of the VBC fiber 200. The displacement can be modulated to change and / or control the beam characteristics of the beam in the VBC 200 in real time. However, this is merely an example of a method of controlling the displacement of the VBC fiber 200 using the piezoelectric transducer 2412, and the claimed subject matter is not limited thereto.

[0150] The grating 2414 can be used to induce disturbances in the light beam propagating in the VBC fiber 200. The grating 2414 can be written into the optical fiber by recording the periodic change of the refractive index into the core. The grating 2414 (e.g., a fiber Bragg grating) can be operated as a filter or a reflector. The long period grating can induce a transition between the co-propagating fiber modes. Therefore, the long period grating can be used to adjust the radiance, intensity profile and / or divergence profile of the light beam composed of one or more modes to couple one or more original modes to one or more different modes with different radiance and / or divergence profiles. The adjustment is achieved by changing the period or amplitude of the refractive index grating. For example, methods such as changing the temperature, bending radius and / or length (e.g., stretching) of the fiber Bragg grating can be used for such adjustment. The VBC fiber 200 with the grating 2414 can be connected to the workbench 2426. The workbench 2426 can be configured to perform any of a variety of functions and can be controlled by the controller 2428. For example, stage 2426 can be coupled to VBC fiber 200 with fasteners 2430 and can be configured to stretch and / or bend VBC fiber 200 to exert leverage using fasteners 2430. Stage 2426 can have an embedded thermal device and can change the temperature of VBC fiber 200.

[0151] Fig.25 An example process 2500 for adjusting and / or maintaining beam characteristics within an optical fiber without using free space optics to adjust the beam characteristics is shown. In block 2502, a first length of optical fiber and / or a beam of light is perturbed to adjust one or more beam characteristics. Process 2500 moves to block 2504, where the beam of light is launched into a second length of optical fiber. Process 2500 moves to block 2506, where the beam of light having the adjusted beam characteristics propagates in the second length of optical fiber. Process 2500 moves to block 2508, where at least a portion of the one or more beam characteristics of the beam of light is maintained within one or more confinement regions of the second length of optical fiber. The first length of optical fiber and the second length of optical fiber may be comprised of the same optical fiber, or may be different optical fibers.

[0152] Fig.29 A beam shaper system 2900 is shown implemented with a beam delivery device 2902 in the form of a VBC fiber 2906 constructed in accordance with the disclosed example represented by the example VBC fiber 100 (see, e.g., Figure 1 for more details). For brevity, Figure 1 Some of the previously described details are further simplified so that Fig.29 Also note that the subscripts "A", "B", "C", and "D" represent different optional configurations of the beam shaper system 2900, which will be explained in the following paragraphs.

[0153] The laser source 2910 emits a light beam 102 ( Figure 1 ), the first length optical fiber 2912 corresponds to the first length optical fiber 104 ( Figure 1 ). The light beam 102 is incident on the VBC fiber 2906. The perturbation device 110, which operates in conjunction with the VBC fiber 2906 and applies different perturbation states (e.g., different amounts or directions) thereto, directs the fiber mode to a position corresponding to the second length of fiber 108 ( Figure 1 ) of different corresponding restricted areas of the second length optical fiber 2920.

[0154] As previously referenced Fig.24As described, the controller 2930 enables the beam shaper system 2900 to selectively move the fiber mode (i.e., intensity distribution) of the light beam 102 to different regions of the input end of the second length of optical fiber 2920. In some embodiments, the controller 2930 includes a computer workstation having an input and output (I / O) device that is suitable for establishing a signal interface with the perturbation device 110 to signal a perturbation state corresponding to a desired beam shape indicated by, for example, a user input. The skilled person will appreciate that the controller 2930 may include a central processing unit (CPU), a field programmable gate array (FPGA), or other control device suitable for performing logical operations. The controller 2930 may also include a non-transitory machine-readable storage medium storing instructions thereon that, when executed, cause the controller 2930 to perform any method or operation described in the present disclosure.

[0155] In the first "A" configuration, the controller 2930 signals the perturbation device 110 to apply a first perturbation state to the VBC fiber 2906 to establish a first selected intensity profile 2940 at the output end of the second length of optical fiber 2920. A Then, having a first selected intensity profile 2940 A The output light beam is transmitted from the processing head 2950 to the workpiece 2960.

[0156] In the subsequent "B" configuration, the controller 2930 signals the perturbation device 110 to apply a second perturbation state to the VBC fiber 2906 that is different from the first perturbation state, thereby establishing a different first selected intensity profile 2940 at the output end of the second length of optical fiber 2920. A The second selected intensity profile 2940 B Thus, the perturbation device 110, in response to a control signal from the controller 2930, applies a selected amount or direction of bend to the VBC fiber 2906 that shifts the fiber mode to a different region of the confinement region (compare Fig. 7A , 8A , 9A and 10A), thereby providing a means of establishing different optional intensity profiles 2970 at the output end of the second length of optical fiber 2920.

[0157] Based on different material properties, different intensity profiles 2970 may be selected. According to some embodiments, the change from one perturbed state to another is indirectly configured, for example, in response to a selected change 2980 in the type of material to be processed or a selected change 2980 in a calibration setting indirectly related to a material of the same or different type as the workpiece 2960. In other embodiments, the change from one perturbed state to another is directly configured, for example, by directly selecting 2990 a desired beam shape (i.e., potentially independent of the material). Thus, a user may simply select a material or a beam shape, for example, through a selection interface 2996 provided by the controller 2930, in order to dynamically change the beam shape. The change may also be made completely or partially autonomously. For simplicity, the resulting intensity distribution selected directly or indirectly is simply referred to as a selected intensity profile. Furthermore, the skilled person will understand that the selection of an intensity distribution is equivalent to the selection of an intensity profile, particularly because a given intensity profile is generally the same at any radial cross-sectional position in a set of azimuthally symmetric confined regions in the set of confined regions.

[0158] Having described and illustrated the general and specific principles of examples of the presently disclosed technology, it should be apparent that these examples can be modified in arrangement and detail without departing from these principles. We claim protection for all modifications and variations that fall within the spirit and scope of the following claims.

Claims

1. A beam shaper system, comprising: a perturbation device configured to receive the light beam from the laser source and perturb the light beam to create a modified light beam having an adjustable beam shape; a machining head configured to receive the modified light beam and apply it to a workpiece; as well as a disturbance controller configured to control the adjustable beam shape between a Gaussian beam shape and a donut-shaped beam shape based on a setting corresponding to a material property of the workpiece, The perturbation device comprises a variable beam characteristic optical fiber, which includes a first length optical fiber and a second length optical fiber, the first length optical fiber and the second length optical fiber are coupled to each other and have first and second refractive index profiles different from each other, respectively, wherein the second refractive index profile is defined by coaxial confinement regions, the coaxial confinement regions are arranged to maintain the modified light beam, wherein each of the coaxial confinement regions includes a high refractive index region isolated by a low refractive index region.

2. The beam shaper system of claim 1, wherein: The adjustable beam shape includes a super-Gaussian beam shape.

3. The beam shaper system of claim 1 , wherein: The adjustable beam shape includes a saddle beam shape.

4. The beam shaper system of claim 1, wherein: The adjustable beam shape includes an annular beam shape.

5. The beam shaper system of claim 1, wherein: The perturbation device is configured to generate the Gaussian beam shape by applying a lowest setting of perturbation available.

6. The beam shaper system of claim 1, wherein: The perturbation device is configured to generate the annular beam shape by applying a highest setting of perturbation available.

7. The beam shaper system of claim 1, wherein: The beam shaper system further comprises a selection interface, wherein the perturbation controller is configured to receive a user input beam selection made in the selection interface.

8. The beam shaper system of claim 1, wherein: The disturbance controller is configured to generate automatic beam selections in response to changes in the material property of the workpiece.

9. A laser system comprising: a beam delivery device configured to produce a selectable intensity profile in response to a controlled perturbation applied to the beam; a variable beam property optical fiber comprising a first length of optical fiber and a second length of optical fiber, the first length of optical fiber and the second length of optical fiber being coupled to each other and having first and second refractive index profiles, respectively, different from each other, wherein the second refractive index profile is defined by coaxial confinement regions arranged to maintain a selected intensity profile of the perturbed optical beam, wherein each of the coaxial confinement regions comprises a high refractive index region isolated by a low refractive index region; as well as A controller for selecting the intensity profile in response to a user input by directing the light beam to different coaxial confinement regions via the controlled perturbation.

10. The laser system of claim 9, wherein: The selected intensity profile is selected from two or more of a Gaussian intensity profile, a super Gaussian intensity profile, a flat-top intensity profile, a saddle-shaped intensity profile, and a ring-shaped intensity profile.

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