CN112505933A

CN112505933A - Rotary light beam generator

Info

Publication number: CN112505933A
Application number: CN202010976272.0A
Authority: CN
Inventors: M.H.穆恩德尔; R.D.福尔哈伯; J.J.莫尔黑德; V.佩蒂特; P.格雷格
Original assignee: Lumentum Operations LLC
Current assignee: Lumentum Operations LLC
Priority date: 2019-09-16
Filing date: 2020-09-15
Publication date: 2021-03-16
Also published as: JP2022116002A; JP2021047399A

Abstract

A fiber optic device may include a core including a major portion and a minor portion. The secondary portion may include at least one insert element inserted into the primary portion at an off-center position relative to the center of the primary portion. The minor portion may be twisted about an axis of the fiber optic device along a length of the fiber optic device. The rate of twist of the minor portion about the axis may increase from the first end of the optical fibre means towards the second end of the optical fibre means. The minor portion twisted about the axis may cause the light beam emitted at the first end of the fiber optic apparatus to be at least partially converted into a rotating light beam at the second end of the fiber optic apparatus.

Description

Rotary light beam generator

Cross Reference to Related Applications

This application claims priority to U.S. provisional patent application No. 62/900992 filed on day 16, 9, 2019 and is part continuation of U.S. patent application No. 16/457018 filed on day 28, 6, 2019, which claims priority to U.S. provisional patent application No. 62/715040 filed on day 6, 8, 2018, and is CIP of U.S. patent application No. 15/802897 (now U.S. patent No. 10429584) filed on day 3, 11, 2017, which claims priority to U.S. provisional patent application No. 62/425431 filed on day 22, 11, 2016, which are incorporated herein by reference in their entirety.

Technical Field

The present disclosure relates to an optical fiber apparatus for generating a light beam having an annular beam shape and an optical fiber apparatus for generating a rotating light beam having an annular beam shape directly in an optical fiber (i.e., without using free-space optics).

Background

The beam profile of a light beam has a significant impact on the processing performance associated with material processing performed using the light beam. For example, a beam with an annular beam profile may achieve excellent metal cutting. However, most fibers transmit a relatively simple beam profile for the light beam. For example, the beam profile may be a gaussian or near-gaussian profile for a low Beam Parameter Product (BPP) laser (e.g., BPP less than or equal to about 3 millimeters by milliradians (mm-mrad)), which may be used to process thin metal plates (e.g., metal plates having a thickness less than or equal to about 3 mm) using a tightly focused beam. As another example, the beam profile may be a top hat profile (sometimes referred to as a flat top) profile of a high BPP laser (e.g., BPP greater than about 3 mm-mrad) that may be used to process thick metal plates (e.g., metal plates greater than about 3mm thick) using a larger beam.

Disclosure of Invention

According to some possible embodiments, the optical fiber device may include a unitary core having a major portion and a minor portion, wherein at least a portion of the minor portion is offset from a center of the unitary core, wherein the unitary core is twisted about an optical axis of the optical fiber device along a length of the optical fiber device, and wherein an index of refraction of the major portion is greater than an index of refraction of the minor portion; and a cladding surrounding the unitary core.

According to some possible embodiments, an optical fiber device may include a unitary core having a main portion, wherein the main portion of the unitary core has a non-circular shape, and wherein the unitary core is twisted about an optical axis of the optical fiber device along a length of the optical fiber device; and a cladding surrounding the unitary core.

According to some possible embodiments, a method may comprise: receiving, by a spinner fiber, a light beam at a first end of the spinner fiber, wherein the spinner fiber comprises a unitary core twisted about an optical axis of the spinner fiber along a length of the spinner fiber; converting, at least in part, the light beam into a rotating light beam by the rotator fiber, wherein the light beam is converted, at least in part, into a rotating light beam as a result of the unitary core twisting about the optical axis; and outputting a rotating beam through the rotator fiber.

According to some possible embodiments, a method may comprise: fabricating a spinner fiber preform having an integral core whose refractive index structure varies angularly with respect to a center of the spinner fiber preform; consolidating the spinner fiber preform to form a consolidated spinner fiber preform; simultaneously drawing and spinning the consolidated spinner fiber preform to form spun spinner fibers; and tapering the spun spinner fiber to form a tapered spun spinner fiber, wherein within the tapered spun spinner fiber, the unitary core rotates about an optical axis of the tapered spun spinner fiber along the length of the tapered spun spinner fiber.

According to some possible embodiments, a method may comprise: fabricating a spinner fiber preform having an integral core whose refractive index structure varies angularly with respect to a center of the spinner fiber preform; consolidating the spinner fiber preform to form a consolidated spinner fiber preform; drawing the consolidated spinner fiber preform to form drawn spinner fibers; and twisting the drawn spinner fiber to form a twisted spinner fiber, wherein within the twisted spinner fiber the unitary core rotates about an optical axis of the twisted spinner fiber along a length of the twisted spinner fiber.

According to some possible embodiments, an optical fiber apparatus may include a core portion that is twisted about an axis of the optical fiber apparatus along a length of the optical fiber apparatus, wherein a center of the core portion is offset from the axis of the optical fiber apparatus along the length of the optical fiber apparatus, wherein a twist rate of the core portion twisted about the axis increases from a first twist rate at a first end of the optical fiber apparatus to a second twist rate at a second end of the optical fiber apparatus, and wherein the core portion twisted about the axis will cause a light beam emitted at the first end of the optical fiber apparatus to be at least partially converted into a rotating light beam at the second end of the optical fiber apparatus; and a cladding layer surrounding the core portion.

According to some possible embodiments, a method may comprise: receiving the light beam at a first end of a spinner fiber through a spinner fiber, wherein the spinner fiber includes a core portion that is twisted about an axis of an optical fiber device along a length of the optical fiber device such that a center of the core portion is offset from the axis of the spinner fiber along the length of the spinner fiber, wherein a rate of twist of the core portion about the axis increases from a first rate of twist at the first end of the spinner fiber to a second rate of twist at a second end of the spinner fiber; converting, at least in part, the light beam into a rotating light beam by the rotator fiber, wherein the light beam is converted, at least in part, into the rotating light beam as a result of the core portion being twisted about the axis; and outputting a rotating beam through the rotator fiber.

According to some possible embodiments, an annular beam generator may comprise: an optical fiber device comprising a core portion twisted about an axis of the optical fiber device along a length of the optical fiber device, the core portion being offset from the axis of the optical fiber device along the length of the optical fiber device, wherein a rate of twist of the core portion about the axis increases along the length of the optical fiber device from a first end of the optical fiber device to a second end of the optical fiber device; and a cladding layer surrounding the core portion.

According to some possible embodiments, a method may include obtaining a fibrous preform comprising a core and a cladding surrounding the core, the core being substantially centered on a central axis of the fibrous preform; removing a portion of the cladding around the core along the length of the fibrous preform; re-sleeving the fibrous preform to form a spinner fibrous preform, wherein within the spinner fibrous preform the center of the core is offset from the central axis of the spinner fibrous preform; and forming a spinner fiber using the spinner fiber preform, wherein within the spinner fiber, a center of the core is offset from an axis of the spinner fiber along a length of the spinner fiber, and wherein within the spinner fiber, the core is twisted about the axis of the spinner fiber along the length of the spinner fiber.

According to some possible embodiments, a method may comprise: forming an opening along a length of the clad rod, the opening being offset from a central axis of the clad rod; inserting a core rod into the opening along the length of the clad rod; consolidating the core rod and the clad rod to form a consolidated spinner fiber preform; and forming a spinner fiber using the spinner fiber preform, wherein within the spinner fiber, a center of the core is offset from an axis of the spinner fiber along a length of the spinner fiber, and wherein within the spinner fiber, the core is twisted about the axis of the spinner fiber along the length of the spinner fiber.

According to some possible embodiments, an optical fiber apparatus may include a core including a primary portion and a secondary portion, wherein the secondary portion includes at least one insertion element inserted within the primary portion, the at least one insertion element being inserted at an eccentric position relative to a center of the primary portion, wherein the secondary portion is twisted about an axis of the optical fiber apparatus along a length of the optical fiber apparatus, wherein a twist rate of the secondary portion twisting about the axis increases from a first twist rate at a first end of the optical fiber apparatus to a second twist rate at a second end of the optical fiber apparatus, and wherein the secondary portion twisting about the axis at least partially converts a light beam emitted at the first end of the optical fiber apparatus into a rotating light beam at the second end of the optical fiber apparatus; and a cladding surrounding the core.

According to some possible embodiments, a method may comprise: receiving the light beam at a first end of the rotator fiber through the rotator fiber, wherein the rotator fiber comprises a core comprising a primary portion and a secondary portion, wherein the secondary portion comprises at least one insertion element inserted within the primary portion, the at least one insertion element being inserted at an eccentric position relative to a center of the primary portion, wherein the secondary portion is twisted about an axis of the rotator fiber along a length of the rotator fiber, and wherein a rate of twist of the secondary portion about the axis is increased from a first rate of twist of the first end of the rotator fiber to a second rate of twist of the second end of the rotator fiber; converting, at least in part, the light beam into a rotating light beam by the rotator fiber, wherein the light beam is converted, at least in part, as a result of the minor portion being twisted about the axis; and outputting a rotating beam through the rotator fiber.

According to some possible embodiments, an annular beam generator may comprise: an optical fiber apparatus comprising: a core comprising a primary portion and a secondary portion, wherein the secondary portion comprises a set of insertion elements inserted within the primary portion, the set of insertion elements being inserted at respective eccentric positions relative to a center of the primary portion, and wherein the secondary portion is twisted about an axis of the optical fiber apparatus along a length of the optical fiber apparatus, wherein a twist rate of the secondary portion twisted about the axis increases from a first twist rate at a first end of the optical fiber apparatus to a second twist rate at a second end of the optical fiber apparatus.

According to some possible embodiments, a method may comprise: providing a fibrous preform comprising a main portion; forming an opening in a major portion of the fibrous preform along a length of the fibrous preform, the opening being offset from a central axis of the fibrous preform; inserting an insert element into an opening of a major portion of the fibrous preform to form a minor portion of the fibrous preform; consolidating, drawing and twisting the fiber preform to produce a twisted spinner fiber, wherein the minor portion is twisted about the axis of the twisted spinner fiber along the length of the twisted spinner fiber due to the twisting.

Drawings

FIGS. 1A and 1B are diagrammatic views relating to an exemplary spinner fiber for producing a rotating beam as described herein;

FIG. 2 is a diagram of an example environment in which a rotator fiber for generating a rotating beam of light may be implemented;

FIG. 3 is a graph showing various low-order guided modes LP of a parabolic graded-index fiber below cut-off_lmA map of an exemplary lateral near-field intensity pattern of (a);

FIGS. 4A and 4B are cross-sectional views of an exemplary spinner fiber for producing a rotating beam of light;

FIG. 5 is a diagram illustrating an example tapered spinner fiber described herein;

FIG. 6 is a flow diagram of an example process of a spun fiber technique for making spinner fibers described herein;

FIG. 7 is a flow diagram of an example process of a twisted fiber technique for making spinner fibers described herein;

8A-8C are diagrams associated with example simulations using various taper lengths of spinner fibers described herein;

FIGS. 9A and 9B are diagrams of additional example rotator fibers for producing a rotating beam of light; and

fig. 10 and 11 are flow diagrams of example processes for manufacturing a spinner fiber with an offset integral core as described herein.

FIG. 12 is a diagram of an example cross-sectional view of an example optical fiber in which two eccentric rod-like secondary portions are inserted into a primary portion surrounded by a cladding portion.

13A-13D are graphs associated with example calculations illustrating the rotating light beams produced by the fiber optic device shown in FIG. 12.

FIG. 14 is a flow chart of an example process for manufacturing a spinner fiber including an insert element as described herein.

Detailed Description

The following detailed description of example embodiments refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements. The embodiments described below are merely examples and are not intended to limit the embodiments to the precise forms disclosed. Instead, implementations are chosen to be described to enable those of ordinary skill in the art to practice the embodiments.

As described above, the beam shape of conventional fiber-delivered light beams is relatively simple (e.g., having a Gaussian or near-Gaussian profile, top-hat profile, etc.). Producing a beam with a relatively higher order beam shape, such as a ring beam shape (i.e., a ring beam), typically requires expensive, specialized, alignment-sensitive free-space optics, such as axicons, helical phase plates, and the like. Moreover, such optics typically need to be located in the processing head, distal to the fiber associated with delivering the beam. The processing head is an opto-mechanical component that is susceptible to acceleration and contamination (e.g., from smoke, metal debris, dust, etc.) and is therefore a less than ideal location for expensive, alignment sensitive, bulky and/or heavy optical elements.

Furthermore, conventional techniques for producing a beam having an annular beam shape typically provide a beam of poor beam quality. For example, conventional techniques may produce beams with too high a BPP, excessive power in the middle of the ring, diffuse beam edges (e.g., with relatively long power radial tails resulting in poor processing quality), and so forth.

Some embodiments described herein provide an optical fiber apparatus (i.e., without any free-space optics) for directly generating a light beam having a ring-beam shape in an optical fiber. More specifically, the generated light beam is a rotating light beam (i.e., a light beam propagating in a fiber in a helical direction), thereby generating a light beam having a ring beam shape. In some embodiments, the rotational characteristics of the light beam may be maintained (e.g., as the light beam exits the optical fiber) such that the laser spot projected from the optical fiber onto the workpiece exhibits, for example, an annular beam profile with sharp edges and high beam quality. In this way, a light beam having an annular beam shape can be directly generated in the optical fiber, contributing to improved material handling.

Fig. 1A and 1B are diagrammatic views relating to an example 100 of a spinner fiber for producing a rotating beam of light as described herein.

The optical fiber device for generating a rotating beam (referred to herein as a spinner fiber) may comprise a unitary core, which may comprise a major portion and a minor portion, wherein at least a portion of the minor portion is offset from the center of the unitary core. An exemplary cross-section of such a spinner fiber is shown in FIG. 1A. In the example shown in fig. 1A, the secondary portions are arranged such that the secondary portions (e.g., the portions having a "+" shaped cross-section) divide the primary portion into four portions. As further shown, the spinner fiber may further comprise a cladding region surrounding the monolithic core.

As shown in fig. 1B, the unitary core (i.e., the major and minor portions) can be twisted along the length of the spinner fiber about the optical axis of the spinner fiber (e.g., the center of the unitary core). In some embodiments, the unitary core twisted about the optical axis at least partially converts an input light beam (e.g., a non-rotating light beam) emitted at the input end of the rotator fiber into a rotating light beam at the output end of the rotator fiber, as described in further detail below.

As further shown in fig. 1B, in some embodiments, a spinner fiber may be disposed between the input fiber and the output fiber. In some embodiments, the input fibers, spinner fibers, and output fibers may be fused together (e.g., using conventional fiber fusion techniques).

In operation, the rotator fiber may receive an input beam from an input fiber. As shown, the input light beam may include light propagating in one or more non-rotating guided modes. As the light propagates through the spinner fiber, and as the integral core twists along the length of the spinner fiber, the spinner fiber produces a rotating beam of light from the input beam. In other words, the rotator fiber may at least partially convert the input light beam into a rotating light beam (e.g., by at least partially converting one or more non-rotating guided modes into at least one rotating guided mode and/or at least one rotating leaky wave). Thus, as shown in FIG. 1B, the rotating beam of light may comprise light propagating in at least one rotationally guided mode and/or at least one rotationally leaky wave.

In some embodiments, the rotating light beam has an annular beam shape due to propagation of light in at least one rotationally guided mode and/or at least one rotationally leaky wave. The rotating beam may be emitted through an output fiber (e.g., for material processing such as metal cutting). Here, the rotational properties of the light beam can be maintained such that the laser spot projected from the output fiber shows an annular beam profile with sharp edges and high beam quality. In this manner, the fiber optic apparatus may generate a rotating beam having an annular beam shape directly in the fiber (i.e., without any free space optics), thereby facilitating improved material processing (e.g., as compared to the conventional techniques described above).

As noted above, fig. 1A and 1B are provided as examples only. Other examples are possible and may differ from the examples described with respect to fig. 1A and 1B. For example, although the unitary core shown in fig. 1A and 1B includes a primary portion and a secondary portion, other embodiments are possible, such as unitary cores that include only a primary portion (e.g., a primary portion having a non-circular shape, a primary portion offset from the optical axis, etc.). Additional details regarding example designs of spinner fibers are described below.

FIG. 2 is a diagram of an example environment 200 in which a rotator fiber for generating a rotating beam of light may be implemented. As shown in fig. 2, environment 200 may include an input fiber 210, a spinner fiber 220, and an output fiber 230.

The input fiber 210 includes an optical fiber for transmitting an input beam (e.g., an input laser beam) to the rotator fiber 220. In some embodiments, the input fiber 210 may be a step-index fiber or a graded-index fiber, and may be designed to carry a light beam near the fiber axis of the input fiber 210. In some embodiments, the input fiber 210 may be connected to the output fiber of the fiber laser, or the input fiber 210 itself may be the output fiber of the fiber laser. Alternatively, in some cases, the input beam may enter the input fiber 210 from free space. In this case, the input fiber 210 may actually be omitted, and the input beam may be directed into the rotator fiber 220 (e.g., instead of the input fiber 210).

In some embodiments, the input beam emitted by the input fiber 210 may take the form of a guided pattern of the core of the input fiber 210, depending on the system design and the design of the input fiber 210. In the case of step index fibers, the guided mode may have a characteristic half divergence angle (θ) in air, measured using the second moment method and satisfying the following cutoff condition:

sin(θ)＜NA，

wherein NA ═ v (n)₁ ²-n₂ ²) Is the numerical aperture, n₁And n₂The refractive indices of the core of the input fiber 210 and the cladding of the input fiber 210, respectively. In the case where the input fiber 210 is a non-step index fiber, the guided mode can be similarly defined using conventional solutions to the wave equation in the fiber.

Whether the input fiber 210 is a step-index fiber or a non-step-index fiber, the guided mode of the weakly-guided, round-core fiber may be the so-called LP mode LP_lmWherein 1 (number of rotational quanta) is an integer greater than or equal to zero (l.gtoreq.0), and m (number of radial quanta) is an integer greater than or equal to one (m.gtoreq.1). The upper limit of l and m may be determined by a cutoff condition associated with the refractive index profile of the input fiber 210 described above.

In some embodiments, the input beam emitted by the input fiber 210 may be a single mode beam or a multimode beam, and may be a polarized beam or a non-polarized beam. Where the input beam is polarized, the input beam may be circularly polarized, as circular polarization may be better maintained in the rotator fiber 220 and/or the output fiber 230 (e.g., as compared to linear or elliptical polarization). In some embodiments, if a linearly polarized output beam is desired, linear polarization may be generated from circular polarization after terminating the output fiber 230 using, for example, a quarter wave plate.

The rotator fiber 220 comprises optical fiber means for at least partially converting an input beam having a first rotational state into an output beam having a second rotational state. For example, the rotator fiber 220 may comprise an optical fiber device for at least partially converting a light beam (e.g., a non-rotating light beam) into a rotating light beam. In some embodiments, the length of the rotator fiber 220 may be relatively short (e.g., less than 1m in length, but greater than 1mm), while the length of the input fiber 210 and the output fiber 230 may be determined by the optical system in which the rotator fiber 220 is deployed (e.g., in the range from about 0.5m to about 100 m). Design aspects associated with the rotating light beam produced by the rotator fiber 220 are described in the following paragraphs, while design aspects associated with the rotator fiber 220 are described below with reference to fig. 4A, 4B, 9A, 9B, and 12.

In some embodiments, the rotating beam of light may include light propagating in one or more rotationally guided modes. The rotation guidance mode is defined as a mode having l ≧ 1 and a certain rotation direction. The definition for a mode with one determined direction of rotation is as follows. For modes where l ≧ 1, the LP mode can be expressed as having sin (l φ) and cos (l φ) dependencies or

Pattern of dependencies, where φ is an angular coordinate. The pattern with l equal to 0 has no angular dependency. The sine and cosine modes are standing waves in the angular direction, with angular nodes and a net rotational direction of zero. The complex exponential mode is an angular traveling wave without angular nodes. These modes have a certain direction of rotation (e.g., clockwise or counterclockwise) that passes through

(+) or (-) is selected.

In some embodiments, for the rotationally guided modes in the rotating beam described herein, m may be equal to 1(m ═ 1) or may be significantly less than l (e.g., less than about 50% of l, less than about 20% of 1, etc.). In some embodiments, using a relatively low value of m (compared to l) may ensure that the spin guide pattern will have a distinct annular shape. In particular, the m-1 rotary steerable mode has no radial nodes other than zero at the origin. In other words, the m-1 rotationally guided mode is a single ring (while the higher m values correspond to a rotationally guided mode of m concentric rings). In some embodiments, the rotator fiber 220 may produce an angular traveling wave with one defined direction of rotation, no angular nodes, and/or zero or few radial nodes.

FIG. 3 is a graph showing various low order guided modes LP of a parabolic graded index fiber below cut-off_lmA graph of an exemplary lateral near-field intensity pattern of (a). The modes of the fiber having other rotationally symmetric index profiles (e.g., step index fiber) may have intensity modes similar to those shown in fig. 3. In FIG. 3, the standing wave (cosine) and traveling wave modes for each m are shown in the left and right columns corresponding to each m, respectively, for l ≧ 1.

In some embodiments, a rotary guide pattern (e.g., represented by a black box in fig. 3) of m-1 may be included in the rotating beam produced by the rotator fiber 220. Note that this set of rotational guidance modes extends to higher values of l (e.g., l 20 and higher). As shown, the m-1 spin-guide pattern has a distinct annular shape with no nodes in any direction. In some embodiments, a rotating guidance mode with a slightly higher m (e.g., m 2, m 3, etc.) may also provide a useful annular beam, particularly for higher values of l. In some embodiments, one or more of the rotationally guided modes included in the rotating beam may have a value of l (l ≧ 10, such as l 15, l 18, l 20, etc.) greater than or equal to 10.

Additionally or alternatively, the rotating light beam may comprise light propagating in one or more rotating leaky waves. Leaky waves are a type of unguided light in an optical fiber (e.g., light that is not guided by the core of the optical fiber). Leakage wave light emitted into the core of the optical fiber may escape into the cladding of the optical fiber. However, in contrast to most non-guided light in optical fibers, leaky wave light leaks relatively slowly from the core to the cladding.

The rotating leaky wave light can have low loss particularly in a relatively wide parameter range. For example, in a step-index silica fiber with NA of 0.10 and a core diameter of 50 micrometers (μm), the rotating leakage wave light with a wavelength of 1030 nanometers (λ -1030 nm) has no radial nodes and a characteristic semi-divergence angle such that sin (θ) -0.11 has a calculated loss of only 0.14 decibels (dB/m) per meter. Thus, although the rotating leakage wave does not meet the criteria for guided modes, the rotating leakage wave can be used for applications where output fiber lengths are on the order of tens of meters or less, such as passive optical power transmission fibers and active amplifier fibers, where losses of up to a few decibels are acceptable. Similar to the case of the rotating guided mode, the rotating leaky wave has one determined direction of rotation and no angular nodes, typically zero or few radial nodes, and may be included in the rotating beam generated by the rotator fiber 220. In some embodiments, one or more rotating leaky waves included in the rotating beam may have l (l ≧ 10, such as l 15, l 18, l 20, etc.) greater than or equal to 10.

In some embodiments, the rotating beam may include a combination of one or more rotating guided modes and/or one or more leaky waves. In some embodiments, where the input beam is a single-mode beam, the rotator fiber 220 may be designed such that the rotating beam comprises a relatively pure (e.g., greater than about 50% pure, greater than about 80% pure, etc.) single rotationally guided mode or a rotating leaky wave, having a particular value/. In other words, in some embodiments, the rotator fiber 220 may be designed such that at least 50% of the input power associated with the input beam is converted into a single rotationally guided mode or a single rotationally leaky wave in the output beam. As described above, the rotating light beam (e.g., including one or more rotating guided modes and/or one or more rotating leaky waves) has an annular shape at the output end of the rotator fiber 220.

Returning to FIG. 2, the output fiber 230 includes an optical fiber for receiving an output beam (e.g., a rotating beam) emitted by the rotator fiber 220. In some embodiments, the output fiber 230 may be a step index fiber, a graded index fiber, or a fiber with a particular refractive index profile, such as a ring-core fiber designed to carry a rotating beam of light with minimal coupling into other modes or leaky waves and/or designed to provide a preferred radial intensity profile. In some embodiments, for example, output fiber 230 may be omitted if the output of the optical system is to be coupled directly into free space (e.g., rather than a fiber).

The number and arrangement of elements shown and described in connection with fig. 2 are provided as examples. Indeed, environment 200 may include additional elements, fewer elements, different elements, differently arranged elements, and/or differently sized elements than shown in fig. 2.

Fig. 4A and 4B are diagrams of

cross-sections

400 and 450, respectively, of an example rotator fiber 220 for producing a rotating beam.

As shown in FIG. 4A, in some embodiments, the spinner fiber 220 may comprise a unitary core 405 including a fiber having an index of refraction n₁E.g., main portions 410-1, 410-2, 410-3, and 410-4 in the example shown in fig. 4A, and has a refractive index n ₃430. The unitary core 405 is described as unitary in that portions of the unitary core 405 (e.g., the primary portion 410 and the secondary portion 430) contact each other such that the portions of the unitary core 405 form a single unit within the spinner fiber 220. As further shown, the spinner fiber 220 may include a core having an index of refraction n surrounding a unitary core 405₂Of the cladding 420. In some embodiments, as shown in cross-section 400, the minor portion 430 may be disposed in the unitary core 405 such that at least a portion of the minor portion 430 is offset from the center of the unitary core 405.

In some embodiments, the unitary core 405 may be twisted about the optical axis of the spinner fiber 220 (e.g., the center of the spinner fiber 220) along the length of the spinner fiber 220 (e.g., in the manner described above and shown in fig. 1B). In some embodiments, the twist rate about the optical axis increases from a first twist rate toward a first end of the rotator fiber 220 (e.g., the end near the input fiber 210) to a second twist rate toward a second end of the rotator fiber 220 (e.g., the end near the output fiber 230). For example, the twist rate toward the input end of the rotator fiber may increase from zero or nearly zero twists per millimeter (e.g., a twist rate of less than or equal to about 0.02 twists per millimeter (about one twist per 50 millimeters)) to about 0.17 twists per millimeter (about one twist per 6 millimeters) or more toward the output end of the rotator fiber 220.

In some embodiments, the spinner fiber 220 may be tapered such that the size (e.g., diameter) of the unitary core 405 substantially matches the size of the core of the input fiber 210 and/or output fiber 230 at the respective end of the spinner fiber 220.

Fig. 5 is a diagram illustrating an example tapered spinner fiber 220. As shown in fig. 5, in some embodiments, the spinner fiber 220 may be tapered such that the size of the spinner fiber 220 at the input end of the spinner fiber 220 (e.g., joined to an end of the input fiber 210 where the degree of twist is zero or near zero) is smaller than the size of the spinner fiber 220 at the output end of the spinner fiber 220 (e.g., joined to an end of the output fiber 230 where the rate of twist is increased compared to the input end).

As further shown in fig. 5, the twist rate of the unitary core 405 about the optical axis may be increased from a first twist rate (e.g., zero or near zero twist rate) toward the input end of the rotator fiber 220 to a second twist rate toward the output end of the rotator fiber 220. As noted above, fig. 5 is provided as an example only. Other examples are possible and may differ from the example described with respect to fig. 5. Although the rotator fiber 220 is shown as being straight in fig. 5, the rotator fiber 220 may have any shape.

Returning to FIG. 4A, in some embodiments, n₁Greater than n₂And n₃And n is₃Is greater than or equal to n₂(n₂≤n₃＜n₁). In other words, n₁Different from (e.g. greater than) n₃And n₂And n is₃May be different from (e.g., greater than or equal to) n₂. This relationship between the refractive indices of the spinner fibers 220 helps to produce a rotating beam of light as the light propagates through the spinner fibers 220. For example, a majority of the input beam may be in the main portion 410 (refractive index n)₁) While a part of the input beam may be in the secondary part 430 (refractive index n)₃) And (4) medium emission. Here, n is due to₁And n₃Are all greater than n₂(refractive index of cladding 420), light emitted in unitary core 405 (e.g., major portion 410 and minor portion 430) may be guided by cladding 420. In addition, since n is₃Less than n₁The minor portion 430 therefore directs the light slightly in the separate portions of the major portion 410 and when the unitary core 405 is twisted about the optical axis, the light will be twisted about the optical axis of the rotator fiber 220 along the length of the rotator fiber 220, producing a rotating beam of light.

In some embodiments, as shown in the example cross-section 400, the secondary portion 430 may divide the primary portion 410 into at least two portions (e.g., such that the secondary portion 430 is between portions of the primary portion 410). In some embodiments, the unitary core 405 may include a main portion 410 having at least two portions (e.g., two portions, three portions, four portions, six portions, etc.). In some embodiments, at least two portions of the main portion 410 may have approximately equal cross-sectional areas. Additionally or alternatively, at least two portions of the main portion 410 may have different cross-sectional areas.

In some embodiments, as shown in the example cross-section 400, the cross-section of the minor portion 430 may be symmetrical with respect to the optical axis of the rotator fiber 220. Alternatively, in some embodiments, the cross-section of the minor portion 430 may be asymmetric with respect to the optical axis of the rotator fiber 220.

In some embodiments, the minor portion 430 may comprise at least three portions, wherein the at least three portions extend in a direction perpendicular to the optical axis of the rotator fiber 220 in the plane of the cross-section of the rotator fiber 220. In some embodiments, a direction in which one of the at least three portions extends may be perpendicular to a direction in which another of the at least three portions extends. For example, referring to cross-section 400, secondary portion 430 may include a horizontal portion, a first vertical portion (e.g., a vertical portion above the horizontal portion of secondary portion 430 in fig. 4A), and a second vertical portion (e.g., a vertical portion below the horizontal portion of secondary portion 430 in fig. 4A). Here, as shown, the horizontal portion, the first vertical portion, and the second vertical portion extend in a direction perpendicular to the optical axis of the spinner fiber 220 in the plane of the cross-section of the spinner fiber 220. As further shown in fig. 4A, the direction in which the horizontal portion extends is perpendicular to the direction in which the first vertical portion extends, and the direction in which the horizontal portion extends is perpendicular to the direction in which the second vertical portion extends.

It is noted that the example cross-section 400 is provided as an example only. In general, the unitary core 405 (e.g., including the major portion 410 and the minor portion 430) may have a refractive index structure that varies angularly with respect to the optical axis of the rotator fiber 220, with the unitary core 405 twisted about the optical axis along the length of the rotator fiber 220. In the example cross-section 400, the angularly varying refractive index structure is a "+" shaped minor portion 430 in the unitary core 405 surrounded by cladding 420. In this example, the secondary portion 430 forms a complete divider, such that the portions of the primary portion 410 are separated by the secondary portion 430.

Another example of an angularly varying index of refraction structure may include a rotator fiber 220 in which the major portion 410 includes a different number of portions separated by minor portions 430, as shown in fig. 4A. In some embodiments, the symmetry of the minor portion 430 in relation to the refractive index structure of the unitary core 405 may be selected based on the desired rotationally guided mode to be included in the rotated output beam. For example, where a rotary guided mode of l-8 is desired, then the symmetry of the minor portion 430 about the optical axis of the rotator fiber 220 may be selected such that the refractive index structure of the unitary core 405 forms a symmetric eight-lobed separator (e.g., such that the major portion 410 includes eight segments). In general, the symmetry of the secondary portion 430 may preferentially create a pattern with l equal to a value of 1 or a multiple thereof. For example, if the spinner fiber 220 includes a minor portion 430 forming a symmetrical four-bladed divider (e.g., such that the major portion 410 includes four portions as shown in cross-section 400), then a mode of l-4 and a mode having a value of l that is a multiple of 4 may be preferentially excited, e.g., l-0, l-8, l-12, l-16, etc.

Yet another example of an angularly varying index of refraction structure may include a rotator fiber 220 in which the minor portion 430 causes the unitary core 405 to have an asymmetric cross-sectional shape with respect to the optical axis of the rotator fiber 220 (e.g., without dividing the major portion 410 into multiple portions).

Other examples of angularly varying index structures may include a spinner fiber 220 in which the major portion 410 and/or minor portion 430 include graded index material, a spinner fiber 220 in which the minor portion 430 forms a partial divider (e.g., a minor portion 430 spanning about 85% of the inner diameter of the cladding 420, such as compared to the full divider shown in example cross-section 400, to form the unitary core 405 to include a single interconnected major portion 410), a spinner fiber 220 including eccentric circular inclusions in the unitary core 405, and so forth.

As another example, and as shown in the example cross-section 450 of fig. 4B, in some embodiments, the spinner fiber 220 may not include the minor portion 430 (e.g., the spinner fiber 220 may not include a fiber having the refractive index n)₃Any material of (a). In other words, in some embodiments, the unitary core 405 may include only the main portion 410. In this case, the angular variation of the refractive index structure may be defined by the non-circular shape of the main portion 410 within the cladding 420 (e.g., a pentagram shaped main portion 410 is shown in the example cross-section 450. typically, the perimeter of the non-circular shape of the main portion 410 may be at least partially concave (e.g., the pentagram shaped main portion 410 includes five concave portions). in this case, the non-circular shape of the unitary core 405 may be twisted along the length of the spinner fiber 220 (e.g., such that the point of the pentagram is rotated about the optical axis of the spinner fiber 220 along the length of the spinner fiber 220.) here, as the non-circular unitary core 405 is twisted about the optical axis, light propagating in the non-circular unitary core 405 (e.g., light propagating within or near the point of the pentagram shown in the example cross-section 450) is twisted about the optical axis of the spinner fiber 220 along the length of the spinner fiber 220, thereby producing a rotating beam. In some embodiments, the spinner fiber 220 including the non-circular unitary core 405 (i.e., the non-circular main portion 410) may be tapered such that the dimensions of the unitary core 405 substantially match the input fibers 210 and/or the output fibers at the respective ends of the spinner fiber 220The size of the core region of the fiber 230.

As noted above, fig. 4A and 4B are provided as examples only. Other examples are possible and may differ from that described with respect to fig. 4A and 4B.

In some embodiments, a rod-in-tube preform assembly method may be used to manufacture a spinner fiber 220 having a cross-section that varies angularly, thereby manufacturing a spinner fiber 220 preform (e.g., using a plurality of discrete glass pieces, each having an appropriate index of refraction). The spinner fiber 220 preforms may then be fused together near the melting point of the glass. The twisting can be performed during fiber drawing using a preformed spinning technique (e.g., similar to those used in certain polarization-maintaining, low birefringence, or chirally coupled core fibers) or after the fiber drawing process by twisting a short length of the rotator fiber 220 while heating the rotator fiber 220 (e.g., during melt tapering). Additional details regarding the manufacture of the spinner fiber 220 are described below with respect to fig. 6 and 7.

In operation, the spinner fiber 220 may receive a light beam at a first end of the spinner fiber 220. As the light beam propagates through the rotator fiber 220, the rotator fiber 220 may at least partially convert the light beam into a rotating light beam and may output the rotating light beam to an output fiber 230.

In some embodiments, the modes of the rotator fiber 220 follow a twisted pattern of angularly varying refractive index structures, meaning that these modes inherently tend to have a rotating characteristic as light propagates through the rotator fiber 220. As a result, when the rotator fiber 220 is engaged into the output fiber 230, the light launched into the output fiber 230 may be in a rotational state comprising one or more rotationally guided modes and/or one or more rotationally leaky waves. The twist rate (Φ, e.g., in revolutions per meter) of the output end of the rotator fiber 220 determines the output divergence half-angle and the approximate rotation state of the rotating beam according to the following relationship:

sin(θ)～2πn₁ RΦ

l～2πR sin(θ)/λ

wherein R isThe effective radius of the rotating guided mode and/or the rotating leaky wave is typically about 10% smaller than the radius of the unitary core 405. Thus, for example, a 100 μm core diameter spinner fiber 220 is used, with a pitch of rotation of 6mm, a core refractive index of 1.450 (e.g. typical for fused silica glass) and an operating wavelength λ 1080nm, with an effective radius of about 45 × 10^-6m (e.g., R-90% × (100/2) ═ 45 × 10^-6m). Here, since the torsion ratio is 166.7 revolutions per meter (for example, 166.7 (1/(6 mm)), sin (θ) to 0.068 radians and l is approximately equal to 18 (for example, l to 18) can be obtained.

The rotation regime of 18 describes a highly rotating beam and an output divergence of 0.068 radians is a typical characteristic of a fiber-conveyed laser beam in industrial applications. The BPP is 3.1mm-rad (e.g., 45 x 0.068 ═ 3.1mm-rad), which is suitable for thin metal machining, while the annular beam shape is also suitable for thick metal machining.

Like any optical fiber, the light guiding capability of the rotator fiber 220 is defined by the NA of the rotator fiber 220, where NA √ (n)₁ ²-n₂ ²). For the above example, to carry the rotating beam as one or more rotationally guided modes, the NA of the rotator fiber 220 should be at least 0.068. Thus, n₂Should be below 1.4484 as is achievable using, for example, doped fused silica. Alternatively, if it is desired to carry the rotating beam as a rotating leaky wave, an NA value slightly less than 0.068 (e.g., a value in the range of about 0.060 to about 0.067) may be used. In some embodiments, the output fiber 230 should also have a suitable NA for guiding the rotating beam as a rotating guided mode and/or rotating leaky wave.

In some embodiments, the mass of the input fiber 210 coupled into the rotator fiber 220 may determine how efficiently to convert the input power (e.g., non-rotating) into a high brightness rotating optical power at the output of the rotator fiber 220 (e.g., as opposed to non-rotating optical propagation that scatters out of the rotator fiber 220 or degrades as a beam of light quality, e.g., including many different modes). To ensure such efficient beam switching, all transitions should be smooth and adiabatic, particularly in three respects.

A first aspect associated with providing an insulating transition is that the core dimensions at the transition from the input fiber 210 to the spinner fiber 220 and from the spinner fiber 220 to the output fiber 230 should be substantially matched so as to transmit the mode and/or leakage waves without significant mode scrambling. Thus, where the core of the input fiber 210 and the core of the output fiber 230 are different sizes, the spinner fiber 220 should be tapered such that the core size of the spinner fiber 220 at the input end and the core size of the spinner fiber 220 at the output end substantially match those of the input fiber 210 and the output fiber 230, respectively (e.g., as described above with respect to fig. 5). In some embodiments, the taper rate may be sufficiently gradual to achieve an adiabatic transition. In some embodiments, a square root taper profile may be used to achieve a relatively short taper while maintaining thermal isolation.

Another aspect related to providing an insulating transition is that the twist rate of the spinner fiber 220 should be zero or near zero at the input end of the spinner fiber 220 (e.g., the end closest to the input fiber 210) and should gradually increase along the length of the spinner fiber 220. For example, the twist rate of the spinner fiber 220 near the input fiber 210 may correspond to a rotational state l of about 2 or less, 0.5 or less, and the like. In some embodiments, the twist rate may increase along the length of the spinner fiber 220 to a maximum twist rate near the output end of the spinner fiber 220 (e.g., the end closest to the output fiber 230). Here, the rate of change of the rate of twist should be slow enough to achieve an adiabatic transition. It is noted that the twist rate does not reach zero or near zero near the output fiber 230 (e.g., because neither the input fiber 210 nor the output fiber 230 has an angularly varying refractive index structure, there is no inherent amount of twist, and the fibers will transmit light having a given rotational state and launched into the fibers (as long as the rotational state is below the cutoff of the fiber).

Yet another aspect related to providing an adiabatic transition is that light directly launched into the secondary portion 430 (if included in the rotator fiber 220) from the input fiber 210 should then be captured by the primary portion 410 so that the light also has a rotating character. In some embodiments, when rotatingThis effect is achieved when the size of the rotor fibers 220 tapers upward from the input fibers 210 to the output fibers 230. Thus, to satisfy the first aspect described above, the core size of the output fiber 230 should be larger than the core size of the input fiber 210. Light initially launched into the secondary portion 430 may be guided by the cladding 420, but the light propagates without being guided through the primary portion 410 and the secondary portion 430. As the core size of the rotator fiber 220 tapers up toward the output fiber 230, the divergence angle of the light decreases inversely with the core size (as is known for any fiber taper), as the divergence angle decreases to the interface of the refractive index of the major portion 410 and the minor portion 430 (i.e., n) as the divergence angle decreases₁-n₃Interface) below the NA defined by the refractive index of the interface, results in more and more of this light being trapped within the main portion 410. In some embodiments, with a properly designed rotator fiber 220 and associated taper ratio, at least 50% (e.g., 80%) of the light emitted into the secondary portion 430 may be captured by the primary portion 410 and obtain rotational characteristics.

FIG. 6 is a flow diagram of an example process 600 of a spun fiber technique for making the spinner fiber 220.

As shown in fig. 6, the process 600 may include fabricating a spinner fiber 220 preform having a unitary core with a refractive index structure that varies at an angle with respect to a center of the spinner fiber 220 preform (block 610). For example, a preform for a fiber cross-sectional structure, such as the preform shown in FIG. 4A, may use four quarter-circles of refractive index n₁At least three glass sheets (e.g., forming the main portion 410) having a refractive index n₃E.g. forming the minor portion 430 and a refractive index n₂E.g., to form cladding 420. Other methods of making the spinner fiber 220 preform are possible.

As further shown in fig. 6, the process 600 may include consolidating the spinner fiber 220 preform to form a consolidated spinner fiber 220 preform (block 620). In some embodiments, a heat source may be used to consolidate the spinner fiber 220 preform (e.g., such that the glass sheets of the spinner fiber 220 preform are fused together). In some embodiments, the spinner fiber 220 preform may be consolidated during the preforming process associated with block 610 or during the stretching and spinning process associated with block 630 described below.

As further shown in fig. 6, the process 600 may include simultaneously stretching and spinning the consolidated spinner fiber 220 preform to form a spun spinner fiber 220 (block 630). In some embodiments, the consolidated spinner fiber 220 preform may be secured in a preform spinner on a fiber stretching tower, and the consolidated spinner fiber 220 preform may be stretched while being spun (e.g., using conventional techniques related to forming so-called spun fibers) to form spun spinner fibers 220.

In some embodiments, the twist rate relative to the fiber draw speed may determine the twist rate in the spun spinner fiber 220. In some embodiments, the spin rate is selected such that the twist rate in the spun spinner fiber 220 is required to spin the light beam. Typical rates of twist may range, for example, from about 50 revolutions per meter to about 2000 revolutions per meter (although slower or faster rates may be used in some cases). In some embodiments, the spun spinner fiber 220 is drawn downward such that the core size (e.g., the diameter of the unitary core 405) is about the same size or slightly smaller than the core size of the output fiber 230.

As further shown in fig. 6, the process 600 may include splicing the spun spinner fiber 220 to an end of the output fiber 230 (block 640). For example, one end of the spun spinner fiber 220 may be fused to one end of the output fiber 230.

As further shown in fig. 6, the process 600 may include tapering the spun spinner fiber 220 to form a tapered spun spinner fiber 220 wherein within the tapered spun spinner fiber 220 the unitary core is rotated about the optical axis of the tapered spun spinner fiber 220 along the length of the tapered spun spinner fiber 220 (block 650).

In some embodiments, a heat source (e.g., a torch, a fuser, etc.) may be used to create a downward taper in the spun spinner fiber 220 to heat and soften the spun spinner fiber 220 such that the size of the core of the spun spinner fiber 220 tapers down to be approximately equal to or slightly larger than the size of the core of the input fiber 210. Here, the tapering inherently reduces the twist rate of the tapered spun spinner fiber 220 (e.g., as shown in fig. 5) so that the twist rate at the input end of the tapered spun spinner fiber 220 can be zero or near zero, thereby achieving a match with the typical non-rotational characteristics of the light beam emitted by the input fiber 210.

As described above, the taper ratio may be selected such that the transition of light propagating through the tapered, spun spinner fiber 220 (e.g., from the first rotational state to the second rotational state) may be adiabatic or nearly adiabatic, e.g., to minimize brightness loss and/or maximize purity of the rotational state produced in the rotating beam by the tapered, spun spinner fiber 220. More specifically, the rate of increase in core size, the increase in twist rate, and the transmission of light from the cladding 420 to the unitary core 405 should be sufficiently gradual to ensure an adiabatic transition. An adiabatic transition may be defined as a transition where making the transition even slower does not result in a significant performance improvement.

In some embodiments, after tapering to form the tapered spun spinner fiber 220, the tapered spun spinner fiber 220 may be spliced (e.g., welded) to one end of the input fiber 210.

For example, using the previously provided values for a 100 μm core diameter tapered spun spinner fiber 220, a 100 μm core diameter output fiber 230 may be spliced to the spinner fiber 220, and the input end of the tapered spun spinner fiber 220 may be tapered to, for example, a 30 μm core diameter to match the 30 μm core input fiber 210. In this example, the rate of twist can be calculated to reduce by this taper to 15 revolutions per meter (e.g., (30/100)²X 166.7 ═ 15 revolutions per meter), resulting in a rotational state of the input end of the rotator fiber 220 of about 0.18(l 0.18), which is effectively a non-rotational state and therefore well matched to the non-rotational input beam carried by the input fiber 210. In some embodiments, the core of the input fiber 210 may be significantly smaller in size thanThe core of the output fiber 230 may have a size (e.g., the core of the input fiber 210 may have a size less than or equal to about 30% of the size of the core of the output fiber 230) such that the rotator fiber 220 will have zero or near zero twist rate at the input end of the rotator fiber 220.

Although fig. 6 shows example blocks of the process 600, in some implementations, the process 600 may include additional blocks, fewer blocks than those depicted in fig. 6, different blocks, or a different arrangement of blocks. Additionally or alternatively, two or more blocks of process 600 may be performed in parallel.

In some embodiments, the process of the spun fiber technique for making the spinner fiber 220 may include: fabricating a spinner fiber preform having an integral core whose refractive index structure varies angularly with respect to a center of the spinner fiber preform; consolidating the spinner fiber preform to form a consolidated spinner fiber preform; simultaneously drawing and spinning the consolidated spinner fiber preform to form spun spinner fibers; and tapering the spun spinner fiber to form a tapered spun spinner fiber, wherein within the tapered spun spinner fiber, the unitary core rotates about an optical axis of the tapered spun spinner fiber along the length of the tapered spun spinner fiber. In some embodiments, the tapered shape of the spun spinner fiber creates an adiabatic transition between the input fiber and the output fiber and an adiabatic transition from the first rotational state to the second rotational state.

Fig. 7 is a flow diagram of an example process 700 of a twisted fiber technique for manufacturing the spinner fiber 220.

As shown in fig. 7, the process 700 may include fabricating a spinner fiber 220 preform having a unitary core with a refractive index structure that varies angularly with respect to a center of the spinner fiber 220 preform (block 710). For example, the spinner fiber 220 preform may be manufactured in a manner similar to that described above in connection with the example process 600.

As further shown in fig. 7, the process 700 may include consolidating the spinner fiber 220 preform to form a consolidated spinner fiber 220 preform (block 720). For example, the spinner fiber 220 preform may be consolidated in a manner similar to that described above in connection with the example process 600.

As further shown in fig. 7, the process 700 may include stretching the consolidated spinner fiber 220 preform to form a stretched spinner fiber 220 (block 730). In some embodiments, the consolidated spinner fiber 220 preform may be stretched using conventional fiber stretching processes without spinning. In some embodiments, the consolidated spinner fiber 220 preform may be drawn downward such that the core of the drawn spinner fiber 220 (e.g., the size of the unitary core 405) is about equal to or slightly smaller than the size of the core of the output fiber 230.

As further shown in fig. 7, the process 700 may include splicing the drawn spinner fiber 220 to an end of the output fiber 230 (block 740). For example, one end of the drawn spinner fiber 220 may be fused to one end of the output fiber 230.

As further shown in fig. 7, the process 700 may include twisting the drawn spinner fiber 220 to form a twisted spinner fiber 220, wherein within the twisted spinner fiber 220 the unitary core is rotated about an optical axis of the twisted spinner fiber along a length of the twisted spinner fiber 220 (block 750).

In some embodiments, the drawn spinner fiber 220 may be twisted while being heated and/or softened using a heat source (e.g., a torch, a fuser, etc.) to produce a twisted spinner fiber 220 having a variable twist rate (e.g., a twist rate that varies from zero or near zero at the input end of the twisted spinner fiber 220 to a desired twist rate at the output end of the twisted spinner fiber 220). In some embodiments, a tapered profile may also be imparted to the twisted spinner fiber 220 to match the dimensions of the twisted spinner fiber 220 to both the input fiber 210 and the output fiber 230.

In some embodiments, after twisting to form the twisted spinner fiber 220, the twisted spinner fiber 220 may be spliced (e.g., fused) to one end of the input fiber 210.

It is noted that process 700 may be more complex than process 600 due to the need to create a variable twist in the twisted spinner fiber 220 rather than a constant twist during the drawing process associated with a tapered spun spinner fiber 220. However, process 700 may provide additional degrees of freedom compared to process 600. For example, the process 700 may allow for the use of input fibers 210 that are larger than the core size of the output fibers 230. As another example, process 700 may allow the twist rate at the input end of the twisted spinner fiber 220 to be zero (e.g., rather than near zero) as compared to process 600, where the twist rate at the input end of the tapered spun spinner fiber is determined by the taper ratio in the spun fiber technology. In some embodiments, a hybrid approach is possible in which the spun spinner fiber 220 is varied by tapering using a heat source and applying additional variable twist to fine tune (or completely eliminate) the twist rate at the input end.

Although fig. 7 shows example blocks of the process 700, in some implementations, the process 700 may include additional blocks, fewer blocks than those depicted in fig. 7, different blocks, or a different arrangement of blocks. Additionally or alternatively, two or more blocks of process 700 may be performed in parallel.

In some embodiments, the process of the twisted fiber technique for making the spinner fiber 220 may include: fabricating a spinner fiber preform having an integral core whose refractive index structure varies angularly with respect to a center of the spinner fiber preform; consolidating the spinner fiber preform to form a consolidated spinner fiber preform; drawing the consolidated spinner fiber preform to form drawn spinner fibers; and twisting the drawn spinner fiber to form a twisted spinner fiber, wherein within the twisted spinner fiber the unitary core rotates about an optical axis of the twisted spinner fiber along a length of the twisted spinner fiber. In some embodiments, the process can further include softening the drawn spinner fiber with a heat source while twisting the drawn spinner fiber, wherein the drawn spinner fiber is twisted such that the twisted spinner fiber has a variable twist rate along the length of the twisted spinner fiber.

Fig. 8A-8C are diagrams associated with example simulations using various taper lengths of the spinner fiber 220. In the simulations associated with FIGS. 8A-8C, the input fiber 210 has a 30 μm core and the output fiber 230 has a 100 μm core. The spinner fiber 220 is a spun spinner fiber tapered with a parabolic profile from a 30 μm core to a 100 μm core and has a twist rate of 166.7 revolutions/m at the output end of the spinner fiber 220. In addition, the input fiber 210 carries six equally filled modes: LP₀₁，LP₀₂，LP₁₁₍₊₎，LP_11(-)，LP₂₁₍₊₎And LP_21(-)Where (+) and (-) denote the two possible rotational directions of the respective patterns. LP₁₁Mode and LP₂₁The modes each have a small number of rotations (l 1 and l 2, respectively), but since all six modes are equally filled, the average rotation state of the input mode mixture is zero. The NA of the cladding of the spinner fiber 220 is 0.22 (e.g., so all relevant modes are strongly guided). The quality of the output beam is characterized by the number of excitation modes.

The spinner fibers 220 of fig. 8A, 8B and 8C were associated with taper lengths of 10mm, 40mm and 80mm, respectively, in order to evaluate the thermal insulation of these taper lengths. Example simulations show that, as required, the output radiation is found almost entirely in the strong rotating mode LP₁₁In the form of (1). The results are shown in fig. 8A-8C, which show the modal power versus the number of revolutions/.

As shown in the figure, the rotating state generated by the rotator fiber is centered at 1-18. However, there is some state distribution as more than one input pattern is populated. In addition, based on comparing FIG. 8A with FIGS. 8B and 8C, it can be seen that the 10mm taper has significantly more excited states than the 40mm taper and the 80mm taper. This result indicates that the 10mm taper may be too short to insulate (i.e., the 10mm taper is too abrupt for changes in the parameters of the rotator fiber 220 from the input end to the output end), resulting in additional modes being excited and reduced brightness and modal purity.

On the other hand, as shown by comparing fig. 8B and 8C, there is little change between a 40mm taper and an 80mm taper. This indicates that both tapers are adiabatic and that the resulting mode profile is near optimal. In fact, considering that six input patterns are filled, in an ideal case, six output patterns will be filled. It can be seen that most of the output fill in the adiabatic taper is indeed captured within about six modes, some of which slightly diffuse into adjacent modes.

Because all of the generated modes are rotational modes, the output points associated with the output of the spinner fibers 220 may be in a clean annular pattern with sharp edges, as desired for more efficient material handling.

8A-8C are provided as examples only. Other examples are possible and may differ from that described with respect to fig. 8A-8C.

In some embodiments, as described above, the rotator fiber 220 may not include the minor portion 430 (i.e., the unitary core 405 may include only the major portion 410), and the center of the unitary core 405 (i.e., the center of the major portion 410) may be offset from the optical axis of the rotator fiber 220 along the length of the rotator fiber 220 in combination with at least partially converting the input beam into a rotating beam. Fig. 9A and 9B are diagrams of an example rotator fiber 220, where the center of the unitary core 405 is offset from the optical axis of the rotator fiber 220.

As shown in fig. 9A and 9B, in some embodiments, the unitary core 205 may include a single main portion 410, and the center of the unitary core 405 (i.e., the center of the signal main portion 410) may be offset from the optical axis of the rotator fiber 220. Such a unitary core 405 is referred to herein as an offset unitary core 405. In some embodiments, the offset unitary core 405 may have a circular cross-section (as shown in fig. 9A and 9B), a rectangular cross-section, an oval cross-section, a circular cross-section, a partial circular cross-section, a wedge-shaped cross-section, or other shapes. The example spinner fiber 220 shown in fig. 9A and 9B may represent, for example, an 80 μm diameter (highly multimode) monolithic core 405 (e.g., having 0.22NA and thousands of modes around a typical operating wavelength of about 1 μm, 1.5 μm, 1.9 μm), with an axis offset by 10 μm from the central axis of the cladding 420 (e.g., 400 μm diameter cladding).

As shown in fig. 9A and 9B, the offset unitary core 405 may be twisted along the length of the spinner fiber 220 (e.g., such that the unitary core 405 rotates about the optical axis of the spinner fiber 220 along the length of the spinner fiber 220). In this case, the angular variation of the refractive index structure may be defined by the offset of the unitary core 405 relative to the optical axis of the rotator fiber 220. Here, as the offset unitary core 405 is twisted about the optical axis, the light propagating in the offset unitary core 405 is twisted about the optical axis of the rotator fiber 220 along the length of the rotator fiber 220, thereby producing a rotating beam of light (e.g., comprising light propagating in at least one rotationally guided mode or at least one rotationally leaky wave) in a manner similar to that described above. In some embodiments, the rotating light beam may have an annular shape at the second end of the rotator fiber 220, as described above.

In some embodiments, the twist rate of the offset unitary core 405 twisting about the optical axis increases from a first twist rate at the first end of the spinner fiber 220 to a second twist rate at the second end of the spinner fiber 220, as described above. In some embodiments, the first twist rate at the first end of the spinner fiber 220 may be less than or equal to one twist per 50 mm. In some embodiments, as shown in fig. 9A, the integral core 405 is offset from the axis of the spinner fiber 220 and twisted about the axis of the spinner fiber 220 along the length of the spinner fiber 220 such that the offset integral core 405 has a helical shape.

In some embodiments, the spinner fiber 220 including the offset unitary core 405 (e.g., a single main section 410 offset from the optical axis) may be tapered such that the dimensions of the unitary core 405 substantially match the dimensions of the core regions of the input fiber 210 and/or the output fiber 230 at the respective ends of the spinner fiber 220. In some embodiments, the spinner fiber 220 may be tapered such that the size of the spinner fiber 220 at a first end of the spinner fiber 220 is smaller than the size of the spinner fiber 220 at a second end of the spinner fiber 220.

In some embodiments, as shown in fig. 9B, the thickness of the cladding 420 around the offset unitary core 405 is not uniform at a given cross-section of the rotator fiber 220 (due to the single main portion 410 being offset from the optical axis). Thus, in some embodiments, the cross-section of the rotator fiber 220 including the offset unitary core 405 may be asymmetric with respect to the optical axis of the rotator fiber 220.

In some embodiments, the spinner fiber 220 including the offset unitary core 405 (e.g., including the single main portion 410) may be relatively simple to manufacture (e.g., as compared to the example spinner fiber shown in fig. 4A). For example, a conventional preform having a central core (e.g., a unitary core 405 including a single main portion 410) may be manufactured, and a portion of the cladding 420 may be ground away so that the unitary core 405 is eccentric. Next, a re-sleeving operation may be performed (if necessary) to add additional cladding material while maintaining the off-axis position of the unitary core 405. Alternatively, an eccentric hole may be drilled in the undoped rod, and a core rod or core/clad rod may be inserted into the eccentric hole. The structure may then be consolidated and drawn into fibers. It is noted that these processes are provided as examples, and other techniques may be used to manufacture the desired spinner fiber 220 with offset integral core 405.

In some embodiments, the output end of the twisted offset monolithic core 405 may be spliced into a suitable conventional non-helical core multimode output fiber 230, thereby preserving the rotational characteristics of the rotating beam. In some embodiments, the radius of the core of the output fiber 230 may match the maximum displacement of the offset unitary core 405. For example, for a monolithic core 405 of 80 μm diameter with a 10 μm offset, the maximum displacement of the monolithic core 405 is 50 μm (e.g., 40 μm radius +10 μm offset is 50 μm), and most of the light inside the offset monolithic core 405 should be located near the 50 μm radius (due to centrifugal force). Thus, in this example, a suitably matched output fiber 230 would be a 50 μm radius (i.e., 100 μm diameter) core fiber. Here, the rotating beam should seamlessly transition from its location constrained at the periphery of the offset integral core 405 to the 50 μm radius of the core of the output fiber 230.

In order to convert the non-rotating input beam at least partially into a rotating beam with maximum efficiency, the above-described techniques may be used. For example, the spinner fiber 220 with offset integral core 405 may be tapered down and joined to the input fiber 210. Using the numbers in the above example, if the core of the input fiber 210 is 30 μm, the rotator fiber 220 with the 80 μm offset

monolithic core

405 and 400 μm cladding 420 can taper down to a 30 μm core, 150 μm cladding. The input fiber 210 may be spliced to the rotator fiber 220 to align the core of the input fiber 210 with the offset integral core 405. Here, since the input fiber 210 may have a centered core, the cladding of the input fiber 210 and the outer edge of the cladding 420 of the rotator fiber 220 may not be aligned when the cores are aligned. As in the above example, the output fiber 230 may have a 100 μm core. For ease of splicing, the cladding of the output fiber 230 may also be 400 μm, and the cladding of the output fiber 230 and the cladding 420 of the rotator fiber 220 may be aligned.

Further, as described above, the pitch of fiber rotation can be selected to provide a desired rate of beam rotation (which corresponds to a particular output NA), and the length of the taper can be selected to optimize output quality. For the above example, using a 6mm rotation pitch, an 80mm linear taper length can be predicted to be 50% LP₀₁、50％LP₀₂Provides a high quality rotating beam. Here, a clear ring structure can be formed both in the near field and in the far field, which means that a large proportion of the rotation modes are excited. Modeling showed that, consistent with the modeling results above, the number of rotations of the excited mode ranged from about 8 to about 20.

Furthermore, as described above, the use of a tapered structure provides both a gradual transition from a non-rotated to a rotated state and a gradual transition from a smaller (e.g., 30 μm) input beam to a larger (e.g., 100 μm ring) output beam. In some embodiments, a square root tapered pattern may be utilized.

In some embodiments, the spinner fiber 220 may be manufactured using a spun fiber technique (e.g., spinning the preform during fiber drawing) and then applying a non-spun taper, or may be manufactured by using a non-spun fiber and applying rotation during the tapering process, as described above.

As with any rotating beam, care needs to be taken to avoid significant bending losses. Thus, the NA of the cladding 420 of the spinner fiber 220 including the offset unitary core 405 may be greater than the divergence of the generated rotating light. In the above example of a 6mm pitch, 100 μm output fiber 230, the output divergence (far field radius) extends to about 0.10 radians. Here, using fibers with NA of 0.12 or more (e.g., 0.15 or more) should provide sufficient margin to prevent bending loss.

It is noted that the effect provided by the offset integral core 405 of the spinner fiber 220 does not require the use of a circular core. For example, another embodiment includes, starting with the "four-bladed" embodiment shown in FIG. 4A, and injecting light into only one of the main sections 410. In this case, only a single main portion 410 actually carries light, and the single main portion 410 is offset from the center of the rotator fiber 220 (e.g., the wedge apex is near the center, and all light-carrying regions are away from the center).

As noted above, fig. 9A and 9B are provided as examples only. Other examples may be different than that described with respect to fig. 9A and 9B.

FIG. 10 is a flow diagram of an example process 1000 of a first technique for manufacturing a spinner fiber 220 including an offset unitary core 405.

As shown in fig. 10, the process 1000 may include obtaining a fibrous preform including a core and a cladding surrounding the core, the core being substantially centered on a central axis of the fibrous preform (block 1010). For example, a fibrous preform may be obtained that includes a circular core and a cladding surrounding the core. Here, the core of the fibrous preform may be substantially centered on the central axis of the fibrous preform.

As further shown in fig. 10, the process 1000 may include removing a portion of the cladding around the core along the length of the fibrous preform (block 1020). For example, a portion of the cladding of the fibrous preform may be abraded along the length of the fibrous preform.

As further shown in fig. 10, the process 1000 may include re-jacketing the fibrous preform to form a spinner fibrous preform in which the center of the core is offset from the central axis of the spinner fibrous preform (block 1030). For example, a re-sleeving operation may be performed to add cladding material to the fibrous preform while maintaining the off-axis position of the core relative to the (offset) central axis of the fibrous preform.

As further shown in fig. 10, the process 1000 may include forming the spinner fiber 220 using a spinner fiber preform, wherein within the spinner fiber 220 a center of a core (e.g., the unitary core 405) is offset from an axis of the spinner fiber 220 along a length of the spinner fiber 220, and wherein within the spinner fiber 220 the offset unitary core 405 is twisted about the axis of the spinner fiber 220 along the length of the spinner fiber 220 (block 1040). In some embodiments, the spinner fibers 220 may be formed using spun fiber techniques (e.g., including simultaneous drawing and spinning), as described above in connection with fig. 6. In some embodiments, the spinner fiber 220 may be formed using a twisted fiber technique (e.g., including drawing and then twisting), as described above in connection with fig. 7.

Although fig. 10 shows example blocks of the process 1000, in some implementations, the process 1000 may include additional blocks, fewer blocks than those depicted in fig. 10, different blocks, or a different arrangement of blocks. Additionally or alternatively, two or more blocks of process 1000 may be performed in parallel.

FIG. 11 is a flow diagram of an example process 1100 of a second technique for manufacturing a spinner fiber 220 including an offset unitary core 405.

As shown in fig. 11, the process 1100 may include forming an opening along a length of the clad rod that is offset from a central axis of the clad rod (block 1110). For example, eccentric holes may be drilled in the (undoped) clad rods.

As further shown in FIG. 11, the process 1100 may include inserting a core rod into the opening along the length of the clad rod (block 1120). For example, the core rod may be inserted into a bore of a clad rod along the length of the clad rod.

As further shown in fig. 11, the process 1100 may include consolidating the core rod and clad rod to form a consolidated spinner fiber preform (block 1130). For example, the core rod and clad rod may be consolidated to form a preform of the spinner fiber 220. In some embodiments, a heat source may be used to consolidate the spinner fiber preform (e.g., to cause the glass sheets of the spinner fiber 220 preform to melt together). In some embodiments, the spinner fiber preform may be consolidated during formation of the spinner fiber 220 in connection with block 1140 described below.

As further shown in fig. 11, the process 1100 may include forming the spinner fiber 220 using a spinner fiber preform, wherein within the spinner fiber 220 a center of a core (e.g., the unitary core 405) is offset from an axis of the spinner fiber 220 along a length of the spinner fiber 220, and wherein within the spinner fiber 220 the offset unitary core 405 is twisted about the axis of the spinner fiber 220 along the length of the spinner fiber 220 (block 1140). In some embodiments, the spinner fibers 220 may be formed using spun fiber techniques (e.g., including simultaneous drawing and spinning), as described above in connection with fig. 6. In some embodiments, the spinner fiber 220 may be formed using a twisted fiber technique (e.g., including drawing followed by twisting), as described above in connection with fig. 7.

Although fig. 11 shows example blocks of the process 1100, in some implementations, the process 1100 may include additional blocks, fewer blocks than those depicted in fig. 11, different blocks, or a different arrangement of blocks. Additionally or alternatively, two or more blocks of process 1100 may be performed in parallel.

In some embodiments, the one or more secondary portions 430 may be implemented as one or more insert elements (e.g., one or more rod-like inserts). In some embodiments, the insertion element may be inserted eccentrically into one or more of the main portions 410. That is, the secondary portion 430 may include at least one insertion element inserted into the primary portion 410 to a position eccentric with respect to the center of the primary portion 410. In some embodiments, the refractive index of the insertion element may be lower than the main portion 410. In some embodiments, the cross-section of the insertion element can be circular (e.g., circular, oval, etc.). In some embodiments, the cross-sectional dimension (e.g., diameter) of a given insertion element may be less than about 5% of the dimension (e.g., cross-sectional diameter) of the main portion 410. In some embodiments, one or more of the insertion elements may be implemented by: one or more corresponding holes are drilled in the preform that makes up the primary portion 410 and/or the cladding 420, one or more insert elements of the secondary portion 430 are inserted into the holes, and the preform is then consolidated and stretched into a fiber. The fibers may then be twisted during drawing or subsequently, as described elsewhere herein.

Fig. 12 is a schematic diagram of an example cross-sectional view 1200 of an example optical fiber in which two eccentric insertion elements (e.g., minor portions 430 in the form of rod-shaped inserts) are inserted into a major portion 410 surrounded by a cladding portion 420. In some embodiments, this design provides a preform that is relatively easy to manufacture (e.g., as compared to the design shown in fig. 4A).

In some embodiments, twisting of the profile shown in fig. 12 along the length of the fiber results in the light beam inside the main portion 410 being converted into a rotating light beam. That is, the eccentric insertion element is twisted about the axis such that the light beam emitted at the first end of the optical fiber is at least partially converted into a rotating light beam at the second end of the optical fiber. In some embodiments, as described above, the twist rate of the one or more insertion element minor portions twisted about the axis of the optical fiber may be increased from a first twist rate at the first end of the optical fiber to a second twist rate at the second end of the optical fiber. As noted above, in some embodiments, the rate of twist may begin at zero or a relatively low rate of twist and gradually increase to a relatively high rate of twist (e.g., over a length between 1mm and 1 m). In some embodiments, the fibers may taper upwardly, as described above. In some embodiments, the input beam may be injected primarily into the major portion 410 rather than the minor portion 430.

As noted above, fig. 12 is provided as an example only. Other examples may differ from those described with respect to fig. 12.

An example calculation demonstrating the rotating beam produced by a fiber optic device using the design shown in fig. 12 is shown in fig. 13A-13D. After fiber tapering based on a fiber having a main portion 410 geometry as shown in FIG. 13A, rotation has been induced to the light beam as represented by the withdrawal of light intensity from the center of the fiber, as shown in the intensity graph in FIG. 13B. Such a beam may transmit a rotating beam (e.g., having a circular shape in the near and far fields) when passed through a standard feed fiber, as shown in fig. 13C and 13D. In some embodiments, the parameters of the rotating light beam (e.g., rotation rate, beam size in the far field, etc.) may be controlled based on the dimensional selection of the optical fiber shown in fig. 13A or based on engineering devices to accelerate the rotation of the refractive index profile.

13A-13D are provided as examples only. Other examples may differ from those described with respect to fig. 13A-13D.

In some embodiments, a given interposer element may comprise doped silica, undoped silica, or another glass having a lower index of refraction than the main portion 410.

In some embodiments, the insert element forming the secondary portion 430 may be a fluid (e.g., a liquid, a gas mixture such as air), or may be a vacuum contained in one or more openings in the primary portion 410. Such an embodiment has a number of advantages. One advantage is that the filler material can be varied to alter the characteristics of the structure. For example, the structure may be changed from rotationally induced to non-rotationally induced (e.g., such that no rotating structure is seen by the light beam) by replacing the low index liquid with a liquid having the same refractive index as the main portion 410. In such a case, fiber engineering techniques may be utilized to allow liquid to flow into and out of the rotating structure (e.g., in real time).

Another advantage of using a fluid to implement the insertion element in the secondary portion 430 is that during the manufacturing process of the optical fiber, the holes in the preform of the primary portion 410 can be selectively and gradually collapsed, causing the insertion element to gradually "open" and "close". For example, if the fiber is drawn and twisted leaving one or more holes open (e.g., filled with air), the one or more holes may be fed into the fiber by applying sufficient heat to the fiber in the desired region (or optionally while applying suction to the one or more holes) during final processing of the fiber optic device210 and/or the output fibers 230 slowly collapse. In this case, the cross-sectional dimension of the one or more insertion elements may increase along a first portion of the optical fiber (e.g., a portion of the optical fiber near the input end) and may decrease along a second portion of the optical fiber (e.g., a portion of the optical fiber near the output end). Thus, in some embodiments, the cross-sectional dimension of one or more insertion elements may vary along at least a portion of the length of the optical fiber. In some embodiments, the cross-sectional dimension (e.g., diameter) of the one or more insertion elements may be zero or near zero at the first end of the optical fiber and at the second end of the optical fiber, and may be substantially greater than zero between the first end and the second end. In this manner, the input beam may be adiabatically or near-adiabatically converted to one or more modes of the rotator fiber 220, and one or more modes of the rotator fiber 220 or one or more leakage waves may be adiabatically or near-adiabatically converted to one or more modes or one or more leakage waves of the output fiber 230. One advantage of this technique is that mode transitions can be closer to ideal. For example, a single input mode (e.g., the basic mode LP) may be used₀₁) Efficient conversion to a single higher order rotation mode (e.g., LP)₈₁Or LP_15，1). Additionally, there may not be any light launched directly into the secondary portion 430 at the input boundary with the input fiber 210, which would otherwise degrade the performance of the fiber optic device. In this embodiment, the one or more holes may be filled with a fluid present in the optical system when the second end of the one or more holes is sealed (e.g. air or vacuum), but may alternatively be filled with a specific gas, a specific gas mixture or a specific liquid, if desired.

Fig. 14 is a flow diagram of an example process 1400 of a technique for manufacturing a spinner fiber 220 including a secondary portion 430 in the form of an insert element, as described herein.

As shown in fig. 14, the process 1400 may include providing a fibrous preform including a main portion 410 (block 1410).

As further shown in fig. 14, the process 1400 may include forming an opening in the main portion 410 of the fibrous preform along the length of the fibrous preform, the opening being offset from a central axis of the fibrous preform (block 1420). In some embodiments, the openings may be formed in the fibrous preform by drilling holes in a major portion of the fibrous preform, as described above.

As further shown in fig. 14, the process 1400 may include inserting an insert element into an opening of the primary portion 410 of the fibrous preform to form the secondary portion 430 of the fibrous preform (block 1430). In some embodiments, the insertion element may be a fluid (e.g., a liquid, a gas mixture such as air) inserted into the opening, or may be a vacuum created such that the vacuum is contained in the opening of the main portion 410, as described above.

As further shown in fig. 14, the process 1400 may include consolidating, stretching, and twisting the fiber preform to produce a twisted spinner fiber, wherein the minor portion 430 (i.e., the insertion element) is twisted about the axis of the twisted spinner fiber along the length of the twisted spinner fiber as a result of the twisting (block 1440).

In some embodiments, a heat source may be used to consolidate the fiber preform (e.g., to cause the glass sheets of the spinner fiber 220 preform to melt together).

In some embodiments, the spinner fiber 220 preform may be stretched using a conventional fiber stretching process without spinning. In some embodiments, the spinner fiber 220 preform may be drawn downward such that the core of the spinner fiber 220 (e.g., the size of the unitary core 405) is about equal to or slightly smaller than the size of the core of the output fiber 230.

In some embodiments, the spinner fiber 220 may be twisted while it is heated and/or softened using a heat source (e.g., a torch, a fuser, etc.) to produce a twisted spinner fiber 220 having a variable twist rate (e.g., a twist rate that varies from zero or near zero at the input end of the twisted spinner fiber 220 to a desired twist rate at the output end of the twisted spinner fiber 220). In some embodiments, a tapered profile may also be imparted to the twisted spinner fiber 220 to match the dimensions of the twisted spinner fiber 220 to both the input fiber 210 and the output fiber 230.

Although fig. 14 shows example blocks of the process 1400, in some implementations, the process 1400 may include additional blocks, fewer blocks than those depicted in fig. 14, different blocks, or a different arrangement of blocks. Additionally or alternatively, two or more blocks of process 1400 may be performed in parallel.

Some embodiments described herein provide an optical fiber apparatus (i.e., without any free-space optics) for directly generating a light beam having a ring-beam shape in an optical fiber. More specifically, the generated light beam is a rotating light beam (i.e., a light beam propagating in a fiber in a helical direction), thereby generating a light beam having a ring beam shape. In some embodiments, the rotational characteristics of the beam may be maintained (e.g., as the beam exits the optical fiber) such that the laser spot projected from the optical fiber onto the workpiece exhibits, for example, an annular beam profile with sharp edges and high beam quality.

The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the embodiments to the precise form disclosed. Modifications and variations are possible in light of the above disclosure or may be acquired from practice of the embodiments.

For example, the rotator fiber 220 has been described for the purpose of converting a non-rotating beam to a rotating beam. However, in some applications, the rotator fiber 220 may be used in the opposite direction to convert an input rotating beam into an output non-rotating beam. This may be accomplished by reversing the design of the rotator fiber 220, including the variations of taper and twist, such that the twist rate at the input end of the rotator fiber 220 matches the rotation of the input beam and such that the twist rate at the output end of the rotator fiber 220 is zero or near zero. Any of the fabrication techniques described above may be applied to this example.

As another example, the rotator fiber 220 may be designed to convert an input beam having any rotational state into an output beam having another (i.e., different) rotational state. The criteria for achieving this is that the twist rate at the input end of the rotator fiber 220 should match the rotational state of the input beam and the twist rate at the output end of the rotator fiber 220 should match the desired rotational state of the output beam. Any of the fabrication techniques described above may be applied to this example.

Even if specific combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure of the various embodiments. In fact, many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. Although each dependent claim listed below may depend directly on only one claim, the disclosure of possible embodiments includes each dependent claim in combination with every other claim in the set of claims.

No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles "a" and "an" are intended to include one or more items, and may be used interchangeably with "one or more". Further, as used herein, the term "set" is intended to include one or more items (e.g., related items, unrelated items, combinations of related and unrelated items, etc.) and may be used interchangeably with "one or more". Where only one item is intended, the term "one" or similar language is used. Also, as used herein, the term "having," variants thereof, and the like are intended to be open-ended terms. Further, the phrase "based on" is intended to mean "based, at least in part, on" unless explicitly stated otherwise.

Claims

1. An optical fiber apparatus comprising:

a core comprising a major portion and a minor portion,

wherein the secondary portion comprises at least one insert element inserted within the primary portion, the at least one insert element being inserted at an off-center position relative to the center of the primary portion,

wherein the secondary portion is twisted about an axis of the optical fiber device along a length of the optical fiber device,

wherein the rate of twist of the secondary portion about the axis increases from a first rate of twist at a first end of the optical fiber arrangement to a second rate of twist at a second end of the optical fiber arrangement, and

wherein the minor portion twisted about the axis will at least partially convert the light beam emitted at the first end of the optical fiber arrangement into a rotating light beam at the second end of the optical fiber arrangement; and

a cladding surrounding the core.

2. The fiber optic apparatus of claim 1, wherein the at least one insert element has a circular cross-section.

3. The fiber optic apparatus of claim 1, wherein the secondary portion includes two or more insertion elements inserted within the primary portion.

4. The fiber optic apparatus of claim 1, wherein the at least one insert element is formed of doped silica or undoped silica.

5. The fiber optic apparatus of claim 1, wherein the at least one insert element comprises a fluid or vacuum contained within an opening of the main portion.

6. The fiber optic apparatus of claim 1, wherein the cross-sectional diameter of the at least one insertion element is less than about 5% of the diameter of the main portion.

7. The fiber optic apparatus of claim 1, wherein a cross-sectional dimension of the at least one insertion element increases along a portion of the length of the fiber optic apparatus in a direction from the first end of the fiber optic apparatus toward the second end of the fiber optic apparatus.

8. The fiber optic apparatus of claim 1, wherein a cross-sectional dimension of the at least one insertion element decreases along a portion of the length of the fiber optic apparatus in a direction from the first end of the fiber optic apparatus toward the second end of the fiber optic apparatus.

9. The fiber optic apparatus of claim 1, wherein the at least one insert element has a cross-sectional dimension approaching zero at the first end of the fiber optic apparatus.

10. The fiber optic apparatus of claim 1, wherein a cross-sectional dimension of the at least one insert element approaches zero at the second end of the fiber optic apparatus.

11. A method, comprising:

the light beam is received at a first end of the spinner fiber by the spinner fiber,

wherein the spinner fiber comprises a core comprising a major portion and a minor portion,

wherein the minor portion is twisted about the axis of the spinner fiber along the length of the spinner fiber, and

wherein the secondary portion twists about the axis at a rate that increases from a first rate at the first end of the spinner fiber to a second rate at the second end of the spinner fiber;

the light beam is at least partially converted into a rotating light beam by the rotator fiber,

wherein the light beam is at least partially converted due to the secondary portion being twisted about the axis; and

a rotating beam is output through the rotator fiber.

12. The method of claim 11, wherein the at least one insert element has a circular cross-section.

13. The method of claim 11, wherein the secondary portion includes six or fewer insertion elements inserted within the primary portion.

14. The method of claim 11, wherein the at least one interposer element is formed of doped silicon dioxide or undoped silicon dioxide.

15. The method of claim 11, wherein the at least one insert element comprises a liquid, a gas mixture, or a vacuum contained within an opening in the main portion.

16. The method of claim 11, wherein the cross-sectional dimension of the at least one insert element increases along a portion of the length of the spinner fiber in a direction from the first end of the spinner fiber toward the second end of the spinner fiber.

17. The method of claim 11, wherein the cross-sectional dimension of the at least one insert element decreases along a portion of the length of the spinner fiber in a direction from the first end of the spinner fiber toward the second end of the spinner fiber.

18. The method of claim 11, wherein the cross-sectional dimension of the at least one insert element approaches zero at the first end of the spinner fiber or at the second end of the spinner fiber.

19. An annular beam generator comprising:

an optical fiber apparatus comprising:

a core comprising a major portion and a minor portion,

wherein the secondary part comprises a set of insertion elements inserted within the main part at respective eccentric positions with respect to the centre of the main part, and

wherein the rate of twist of the secondary portion about the axis increases from a first rate of twist at the first end of the optical fiber arrangement to a second rate of twist at the second end of the optical fiber arrangement.

20. The annular beam generator of claim 19, wherein the set of insert elements vary in cross-sectional dimension along a portion of the length of the optical fiber device from the first end of the optical fiber device toward the second end of the optical fiber device.

21. A method, comprising:

providing a fibrous preform comprising a main portion;

forming an opening in a major portion of the fibrous preform along a length of the fibrous preform, the opening being offset from a central axis of the fibrous preform;

inserting an insert element into an opening of a major portion of the fibrous preform to form a minor portion of the fibrous preform;

consolidating, stretching and twisting the fibrous preform, to produce a twisted spinner fiber,

wherein the minor portion twists about the axis of the twisted spinner fiber along the length of the twisted spinner fiber due to the twisting.