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WO-2026096059-A1 - MONOLITHIC MODE FIELD ADAPTER AND COUPLER

WO2026096059A1WO 2026096059 A1WO2026096059 A1WO 2026096059A1WO-2026096059-A1

Abstract

An optical coupler may include one or more gradient refractive index (GRIN) elements having spatially-varying refractive index profiles orthogonal to a propagation direction and one or more solid propagation elements having spatially-uniform refractive index profiles orthogonal to a propagation direction. The one or more GRIN elements and the one or more solid propagation elements are joined along the propagation direction to form a monolithic element. The one or more GRIN elements and the one or more solid propagation elements may be configured to couple light between outer faces of the monolithic element distributed along the propagation direction.

Inventors

  • Bate, Timothy
  • AMEZCUA-CORREA, Rodrigo
  • ANTONIO-LOPEZ, Jose Enrique
  • BANDRES, MIGUEL A.
  • LEIJA, Armando Perez

Assignees

  • UNIVERSITY OF CENTRAL FLORIDA RESEARCH FOUNDATION, INC.

Dates

Publication Date
20260507
Application Date
20250829
Priority Date
20250829

Claims (20)

  1. CLAIMS
  2. What is claimed:
  3. 1. An optical coupler, comprising:
  4. one or more gradient refractive index (GRIN) elements having spatially-varying refractive index profiles orthogonal to a propagation direction; and
  5. one or more solid propagation elements having spatially-uniform refractive index profiles orthogonal to a propagation direction, wherein the one or more GRIN elements and the one or more solid propagation elements are joined along the propagation direction to form a monolithic element, wherein the one or more GRIN elements and the one or more solid propagation elements couple light between outer faces of the monolithic element distributed along the propagation direction,
  6. 2. The optical coupler of claim 1, wherein at least one of dioptric powers of the one or more GRIN elements, lengths of the one or more GRIN elements, or lengths of the one or more solid propagation elements are selected to adapt a mode profile of light from a first external optical element coupled to a first of the outer faces to match a mode profile of a second external optical element coupled to a second of the outer faces.
  7. 3. The optical coupler of claim 1, wherein the outer faces are couplable with a first external optical element and a second external optical element.
  8. 4. The optical coupler of claim 3, wherein at least one of the first external optical element or the second external optical element is a hollow-core fiber.
  9. 5. The optical coupler of claim 3, wherein at least one of the first external optical element or the second external optical element is a solid-core fiber. 6. The optical coupler of claim 3, wherein the first external optical element and the second external optical element are solid-core fibers with at least one of different mode profiles or different mode field diameters.
  10. 7. The optical coupler of claim 1, wherein the one or more GRIN elements are interleaved with the one or more solid propagation elements.
  11. 8. The optical coupler of claim 1, wherein the one or more solid propagation elements include a first solid propagation element, a second solid propagation element, and a third solid propagation element, wherein the one or more GRIN elements include a first GRIN element between the first and second solid propagation elements along with a second GRIN element between the second and third solid propagation elements.
  12. 9. The optical coupler of claim 1, wherein the optical coupler operates as an imaging system.
  13. 10. The optical coupler of claim 1, wherein the optical coupler operates as a 4F imaging system.
  14. 11. The optical coupler of claim 1, further comprising:
  15. one or more anti-reflection treatments on at least one of the outer faces or interfaces within the optical coupler.
  16. 12. The optical coupler of claim 11, wherein the one or more anti-reflection treatments comprise:
  17. at least one of an anti-reflection coating, a surface treatment, or an angle-cleaved surface.
  18. 13. The optical coupler of claim 1, further comprising: an exterior connector configured to mechanically couple with a paired connector on a first external optical element, wherein mechanically coupling the exterior connector to the paired connector provides optical coupling of light between the first optical element and a first of the outer faces.
  19. 14. The optical coupler of claim 13, wherein the exterior connector and the paired connector are at least one of LC, FC, SC, or ST connectors.
  20. 15. The optical coupler of claim 13, further comprising:

Description

MONOLITHIC MODE FIELD ADAPTER AND COUPLER CROSS-REFERENCE TO RELATED APPLICATION [0001] The present application claims the benefit of U. S. Non-Provisional Patent Application 19/314,660 filed on August 29, 2025, and claims the benefit of U. S. Provisional Patent Application 63/713,325 filed on October 29, 2025; U. S. NonProvisional Patent Application 19/314,660 filed on August 29, 2025 also claims the benefit of U. S. Provisional Patent Application 63/713,325 filed on October 29, 2025; U. S. Non-Provisional Patent Application 19/314,660 and U. S. Provisional Patent Application 63/713,325 are both incorporated herein by reference in their entireties. GOVERNMENT LICENSE RIGHTS [0002] This invention was made with government support under Grant Number W911NF-24- 1-0008 awarded by the Army Research Office (ARO). The government has certain rights in the invention. TECHNICAL FIELD [0003] The present disclosure relates generally to an optical coupler and, more particularly, to a monolithic all-fiber coupler. BACKGROUND [0004] It is often desirable to couple optical fibers with different optical mode profiles due to differences in size and/or design. However, existing solutions suffer from precise alignment requirements, a lack of mechanical stability, requirements to modify fibers being coupled (e.g., to provide thermally expanded cores, fiber tapers), and/or bulk optical elements. Further, many existing solutions require a relatively high degree of skill to implement. [0005] For example, mechanical spacers suffer from mechanical vibrations, which may degrade coupling performance. As another example, modifying the fibers to be coupled requires specialty equipment and expertise. As another example, multimode interference in a gradient index core fiber requires extremely precise lengths of fiber and further requires that the initial and final mode fields are supported by the graded index core fiber. Multimode interference also suffers from focusing light before expanding it under some conditions, which makes it nonviable in high power laser applications. [0006] There is therefore a need to develop systems and methods to cure the above deficiencies. SUMMARY [0007] In some embodiments, an optical coupler is provided. The optical coupler may include one or more gradient refractive index (GRIN) elements having spatially-varying refractive index profiles orthogonal to a propagation direction. The optical coupler may include one or more solid propagation elements having spatially-uniform refractive index profiles orthogonal to a propagation direction. The one or more GRIN elements and the one or more solid propagation elements may be joined along the propagation direction to form a monolithic element. The one or more GRIN elements and the one or more solid propagation elements may couple light between outer faces of the monolithic element distributed along the propagation direction. [0008] In some embodiments, at least one of dioptric powers of the one or more GRIN elements, lengths of the one or more GRIN elements, or lengths of the one or more solid propagation elements may be selected to adapt a mode profile of light from a first external optical element coupled to a first of the outer faces to match a mode profile of a second external optical element coupled to a second of the outer faces. [0009] In some embodiments, the outer faces may be couplable with a first external optical element and a second external optical element. [0010] In some embodiments, at least one of the first external optical element or the second external optical element may be a hollow-core fiber. [0011] In some embodiments, at least one of the first external optical element or the second external optical element may be a solid-core fiber. [0012] In some embodiments, the first external optical element and the second external optical element may be solid-core fibers with at least one of different mode profiles or different mode field diameters. [0013] In some embodiments, the one or more GRIN elements may be interleaved with the one or more solid propagation elements. [0014] In some embodiments, the one or more solid propagation elements may include a first solid propagation element, a second solid propagation element, and a third solid propagation element. The one or more GRIN elements may include a first GRIN element between the first and second solid propagation elements along with a second GRIN element between the second and third solid propagation elements. [0015] In some embodiments, the optical coupler may operate as an imaging system. [0016] In some embodiments, the optical coupler may operate as a 4F imaging system. [0017] In some embodiments, the optical coupler may further include one or more anti-reflection treatments on at least one of the outer faces or interfaces within the optical coupler. [0018] In some embodiments, the one or more anti-reflection treatments may include at least one of an anti-reflection coating, a surface tr