US-12625323-B2 - In-fiber optical microresonators and couplers

Abstract

A method for forming an optical fiber having at least one of a microresonator and a coupler integrated therein is described. The method includes providing an optical fiber having a light guiding core. modifying at least one region of the optical fiber using a laser, immersing the optical fiber having the at least one region as modified inside an etchant that selectively etches the at least one region as modified to generate at least one of a microresonator and a coupler integrated in the optical fiber, and removing the optical fiber from the etchant. The optical fiber as removed from the etchant may include the at least one of the microresonator and the coupler. The method may further include heating the optical fiber using, for example, a CO 2 laser or other heating apparatus, to smoothen surface irregularities of at least one of the microresonator and the coupler.

Inventors

• Shuo Yang
• Anbo Wang

Assignees

• VIRGINIA TECH INTELLECTUAL PROPERTIES, INC.

Dates

Publication Date

20260512

Application Date

20220331

Claims (18)

1. 1 . A method for forming an optical fiber having at least one microresonator and at least one coupler integrated therein, comprising: providing an optical fiber having a light guiding core; modifying a first region of the optical fiber as an intended region for the at least one microresonator and a second region of the optical fiber as an intended region for the at least one coupler using an ultrafast laser; immersing the optical fiber having the first region and the second region as modified inside an etchant to selectively etch the first region and the second region as modified and thereby shape the at least one microresonator and the at least one coupler integrated in the optical fiber at the light guiding core, wherein the etchant is hydrofluoric acid (HF), potassium hydroxide (KOH), or a combination thereof; removing the optical fiber from the etchant; and heating the optical fiber to smoothen surface irregularities of the at least one microresonator and the at least one coupler, wherein heating the optical fiber comprises performing at leastone of: a laser reflow process on the optical fiberusinga carbon dioxide (CO 2 ) laser to irradiate and heat the optical fiber and direct heating using a heating apparatus, wherein the heating apparatus is at least one of a furnace, electric arcs, and a flame, wherein the at least one microresonator comprises at least two microresonators that share a common coupler and are oriented in different azimuthal dimensions from one another.
2. 2 . The method according to claim 1 , wherein modifyingthe first region and the second region of the optical fiber using the ultrafast laser comprises: adjusting a pulse width of the ultrafast laser to a femtosecond setting or a picosecond setting; and adjusting a wavelength of the ultrafast laser to ultraviolet, visible, or near-infrared.
3. 3 . The method according to claim 1 , wherein: the at least one microresonator has a shape selected from a group consisting of: a sphere, a cylinder, a toroid, and a polygon; and the at least one coupler is one of: a waveguide coupler; a free-space coupler, and a total-internal-reflection (TIR) coupler.
4. 4 . An optical fiber formed according to the method of claim 1 .
5. 5 . The optical fiber according to claim 4 , wherein: the microresonator is a first microresonator; the optical fiber comprises a second microresonator; and the coupler couples the first microresonator and the second microresonator.
6. 6 . The optical fiber according to claim 5 , wherein the coupler couples the first microresonator and the second microresonator in an axial dimension.
7. 7 . A method for forming an optical fiber having at least one of a microresonator and a coupler integrated therein, comprising: providing an optical fiber having a light guiding core; modifying at least one region of the optical fiber using a laser; immersing the optical fiber having the at least one region as modified inside an etchant to selectively etch the at least one region as modified and thereby shape at least one of the microresonator and the coupler integrated in the optical fiber at the light guiding core; and removing the optical fiber from the etchant, wherein the optical fiber as removed from the etchant comprises the at least one of the microresonator and the coupler, wherein the microresonator comprises at least two microresonators that share a common coupler and are oriented in different azimuthal dimensions from one another.
8. 8 . The method according to claim 7 , further comprising, after removing the optical fiber from the etchant, heating the optical fiber to smoothen surface irregularities of the at least one of the microresonator and the coupler.
9. 9 . The method accordingto claim 8 , wherein heating the optical fiber comprises at least one of: performing a laser reflow process on the optical fiber using a carbon dioxide (CO 2 ) laser to irradiates and heat the optical fiber and direct heating using a heating apparatus, wherein the heating apparatus is one of a furnace, electric arcs, and a flame.
10. 10 . The method according to claim 7 , modifying the at least one region of the optical fiber using the laser comprises: adjusting a pulse width of the laserto a femtosecond setting or a picosecond setting, and adjusting a wavelength of the laser to ultraviolet, visible, or near-infrared, wherein the laser is an ultrafast laser.
11. 11 . The method according to claim 7 , wherein the etchant is hydrofluoric acid (HF), potassium hydroxide (KOH), or a combination thereof.
12. 12 . The method according to claim 7 , wherein the optical fiber comprises a glass fiber, and wherein the glass fiber is formed from pure-fused silica.
13. 13 . The method according to claim 7 , wherein the optical fiber comprises a glass fiber, and wherein the glass fiber is formed from doped silica doped using a dopant selected from a group consisting of: germanium (Ge), phosphorus (P), fluorine (F), and rare earth ions (erbium (Er), ytterbium (Yb), neodymium (Nd), thulium (Tm), praseodymium (Pr), and holmium (Ho).
14. 14 . The method according to claim 7 , wherein: a shape of the optical fiber is one of cylindrical, rectangular, triangular, and polygonal; and a size of the optical fiber is in a range of tens of micrometers or tens of sub-millimeters.
15. 15 . The method according to claim 7 , wherein: the optical fiber comprises the microresonator and the coupler; the microresonator has a shape selected from a group consisting of: a sphere, a cylinder, a toroid, and a polygon; and the coupler is one of: a waveguide coupler; a free-space coupler; and a total-internal-reflection (TIR) coupler.
16. 16 . The method according to claim 7 , wherein: the optical fiber comprises the microresonator, the microresonator being one of a plurality of microresonators integrated in the optical fiber; and the optical fiber comprises the coupler, the coupler being one of a plurality of couplers integrated in the optical fiber.
17. 17 . An optical fiber formed according to the method of claim 7 .
18. 18 . The optical fiber according to claim 17 , wherein: the optical fiber comprises both the microresonator and the coupler; the microresonator is a first microresonator; the optical fiber further comprises a second microresonator; and the coupler couples the first microresonator and the second microresonator.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is a 371 U.S. National Stage Application of PCT Application Serial Number PCT/US2022/022724 filed on Mar. 31, 2022, which application claims the benefit of and priority to U.S. Provisional Patent Application No. 63/170, 160 filed Apr. 2, 2021 entitled “IN-FIBER OPTICAL MICRORESONATORS,” the contents of both of which being incorporated by reference in their entirety herein. BACKGROUND Optical-fiber cables include cables having one or more optical fibers that are used to carry light for purposes of long-distance communication, high-speed data transmission, sensing, and the like. Optical fibers may include resonating cavities, referred to as optical resonators (or simply resonators) which provide an arrangement of glass or mirrors that manipulate light waves. Based on manipulations of light, resonators provide various feedback and measurements relating to a signal transmitted by an optical fiber. Today, manipulating an optical fiber to include a resonator is an incredibly delicate and burdensome task, often requiring cladding or other material to be surgically removed and portions of the optical fiber to be etched physically using a sharp tool or chemically with a compatible etchant. BRIEF SUMMARY Various embodiments are disclosed for in-fiber optical microresonators, couplers, and like components. In a first aspect, a method for forming an optical fiber having a microresonator and a coupler integrated therein is described that includes providing an optical fiber having a light guiding core, modifying a first region of the optical fiber as an intended region for the microresonator and a second region of the optical fiber as an intended region for the coupler using an ultrafast laser, immersing the optical fiber having the first region and the second region as modified inside an etchant that selectively etches the first region and the second region as modified to generate the microresonator and the coupler integrated in the optical fiber at the light guiding core, wherein the etchant is hydrofluoric acid (HF), potassium hydroxide (KOH), or a combination thereof, removing the optical fiber from the etchant, and heating the optical fiber to smoothen surface irregularities of the microresonator and the coupler, wherein heating the optical fiber comprises performing a laser reflow process on the optical fiber using a carbon dioxide (CO2) laser that irradiates and heats the optical fiber, or performing direct heating wherein the heating apparatus is a furnace, electric arcs, flame, or a combination thereof. Modifying the first region and the second region of the optical fiber using the ultrafast laser may include adjusting a pulse width of the ultrafast laser to a femtosecond or a picosecond setting, and adjusting a wavelength of the ultrafast laser to ultraviolet, visible, or near-infrared. The microresonator may have a shape selected from a group consisting of a sphere, a cylinder, a toroid, and a polygon, and the coupler may be one of a waveguide coupler, a free-space coupler; and a total-internal-reflection (TIR) coupler. In some aspects, the microresonator may be a first microresonator, the optical fiber includes a second microresonator; and the coupler couples the first microresonator and the second microresonator. The coupler may couple the first microresonator and the second microresonator in an axial dimension, for example, or in an azimuthal dimension. Further, it is understood that the coupler may couple three or more microresonators in an axial dimension, in an azimuthal dimension, or a combination thereof. In a second aspect, a method for forming an optical fiber having at least one of a microresonator and a coupler integrated therein is described that includes providing an optical fiber having a light guiding core, modifying at least one region of the optical fiber using a laser, immersing the optical fiber having the at least one region as modified inside an etchant that selectively etches the at least one region as modified to generate at least one of a microresonator and a coupler integrated in the optical fiber at the light guiding core, and removing the optical fiber from the etchant, wherein the optical fiber as removed from the etchant comprises the at least one of the microresonator and the coupler. The method may further include, after removing the optical fiber from the etchant, heating the optical fiber to smoothen surface irregularities of the at least one of the microresonator and the coupler. Heating the optical fiber may include, for example, performing a laser reflow process on the optical fiber using a carbon dioxide (CO2) laser that heats and irradiates the optical fiber, or performing direct heating wherein the heating apparatus is a furnace, electric arcs, a flame, a CO2 laser, or a combination thereof. Modifying the at least one region of the optical fiber using the laser may include adjusting a pulse width of the laser to a f