Adjustable beam characteristics

1. A method comprising:

perturbing an optical beam propagating within a first length of fiber to adjust one or more beam characteristics of the optical beam in the first length of fiber or a second length of fiber or a combination thereof;

coupling the perturbed optical beam into the second length of fiber; and

maintaining at least a portion of one or more adjusted beam characteristics within the second length of fiber having two or more confinement regions, wherein the first length of fiber and the second length of fiber form at least a portion of a continuous length of fiber.

2. The method of claim 1 , further comprising generating a selected output beam from the second length of fiber having the adjusted beam characteristics responsive to a selection of a first refractive index profile (RIP) of the first length of fiber or a second RIP of the second length of fiber or a combination thereof.

3. The method of claim 1 , wherein the one or more beam characteristics of the perturbed optical beam are adjusted based on selection of one or more core dimensions of the first length of fiber or one or more confinement region dimensions of the second length of fiber or a combination thereof to generate an adjusted optical beam responsive to perturbing the first length of fiber, the adjusted optical beam having a particular adjusted: beam diameter, divergence distribution, beam parameter product (BPP), intensity distribution, luminance, beam quality factor M 2 , numerical aperture (NA), optical intensity, power density, radial beam position, radiance, or spot size, or any combination thereof at an output of the second length of fiber.

4. The method of claim 2 , wherein the perturbing the optical beam further comprises bending the first length of fiber to alter a bend radius or alter a length of a bent region of the first length of fiber or a combination thereof such that one or more modes of the optical beam are displaced radially with respect to a longitudinal axis of the first length of fiber wherein the two or more confinement regions of the second length of fiber have refractive indices that define a first confinement region and a second confinement region.

5. The method of claim 4 , wherein the one or more adjusted beam characteristics are produced by confining the optical beam in the two or more confinement regions of the second length of fiber.

6. The method of claim 4 , further comprising launching the perturbed optical beam from the first length of fiber into the first confinement region or the second confinement region or a combination thereof such that one or more displaced modes of the optical beam are selectively coupled into and maintained in the first confinement region or the second confinement region, or a combination thereof.

7. The method of claim 1 , wherein perturbing the one or more beam characteristics of the optical beam further comprises perturbing the first length of fiber or the optical beam in the first length of fiber or a combination thereof to adjust at least one beam characteristic of the optical beam at an output of the second length of fiber.

8. The method of claim 7 , wherein the perturbing the first length of fiber further comprises bending, bending over a particular length, micro-bending, applying acousto-optic excitation, thermal perturbation, stretching, or applying piezo-electric perturbation, or any combination thereof.

9. The method of claim 1 , wherein the two or more confinement regions of the second length of fiber comprises a first confinement region comprising a central core and a second confinement region comprising an annular core encompassing the first confinement region.

10. The method of claim 1 , wherein adjusting the one or more beam characteristics of the optical beam further comprises selecting a RIP of the first length of fiber to generate a desired mode shape of a lowest order mode, one or more higher order modes, or a combination thereof.

11. The method of claim 1 , wherein the first length of fiber has a core with a parabolic index profile radially spanning some or all of the core.

12. The method of claim 1 , wherein a RIP of the first length of fiber is selected to increase or decrease a width of the lowest order mode, the higher order modes, or a combination thereof responsive to the perturbing the optical beam.

13. The method of claim 1 , wherein the first length of fiber or the second length of fiber or a combination thereof include at least one divergence structure configured to modify a divergence profile of the optical beam.

14. The method of claim 13 , wherein the confinement regions are separated by one or more cladding structures and wherein the divergence structure is disposed within at least one confinement region separate from the cladding structure and comprising material having a lower index than the confinement region adjacent to the divergence structure.

15. The method of claim 1 , wherein the second length of fiber is azimuthally asymmetric.

16. A method comprising:

perturbing an optical beam propagating within a first length of fiber to adjust one or more beam characteristics of the optical beam in the first length of fiber or a second length of fiber or a combination thereof, wherein the second length of fiber has two or more confinement regions;

coupling the perturbed optical beam into the second length of fiber; and

maintaining at least a portion of one or more adjusted beam characteristics within the second length of fiber, wherein the first length of fiber and the second length of fiber have different RIPs and form at least a portion of a continuous length of fiber.

17. The method of claim 1 , further comprising generating a selected output beam from the second length of fiber having the adjusted beam characteristics responsive to a selection of a first RIP of the first length of fiber or a second RIP of the second length of fiber or a combination thereof.

18. The method of claim 1 , wherein the one or more beam characteristics of the perturbed optical beam are adjusted based on selection of one or more core dimensions of the first length of fiber or one or more confinement region dimensions of the second length of fiber or a combination thereof to generate an adjusted optical beam responsive to perturbing the first length of fiber, the adjusted optical beam having a particular adjusted: beam diameter, divergence distribution, beam parameter product (BPP), intensity distribution, luminance, beam quality factor M 2 , numerical aperture (NA), optical intensity, power density, radial beam position, radiance, or spot size, or any combination thereof at an output of the second length of fiber.

19. The method of claim 17 , wherein the perturbing the optical beam further comprises bending the first length of fiber to alter a bend radius or alter a length of a bent region of the first length of fiber or a combination thereof such that one or more modes of the optical beam are displaced radially with respect to a longitudinal axis of the first length of fiber wherein the two or more confinement regions of the second length of fiber have refractive indices that define a first confinement region and a second confinement region.

20. The method of claim 19 , wherein the one or more adjusted beam characteristics are produced by confining the optical beam in one or more confinement regions of the second length of fiber.

21. The method of claim 16 , wherein the first length of fiber or the second length of fiber or a combination thereof include at least one divergence structure configured to modify a divergence profile of the optical beam.

22. The method of claim 21 , wherein the one or more confinement regions are separated by one or more cladding structures and wherein the divergence structure is disposed within at least one confinement region separate from the cladding structure and comprising material having a lower index than the confinement region adjacent to the divergence structure.

23. The method of claim 16 , wherein the second length of fiber is azimuthally asymmetric.