US-12620766-B2 - Counter pumping a large mode area fiber laser

Abstract

A fiber support assembly includes: a first glass tube, wherein the first glass tube is attached to a microlens or lenslet of a microlens or lenslet array; a second glass tube at least partially disposed within the first glass tube; and a gain fiber disposed within the second glass tube, wherein the gain fiber has a first tapered end cap, and wherein the gain fiber with the first tapered end cap is aligned to the microlens or lenslet attached to the first glass tube. The fiber support assembly may further include: a pump fiber disposed within the second glass tube, wherein the pump fiber has a second tapered end cap; and a reflector configured to receive counter-pumping light from the pump fiber and direct the counter-pumping light to the first tapered end cap of the gain fiber.

Inventors

• Donald Lee Sipes, JR.
• Jason Tafoya
• Brian Michael Schulz
• James LEFORT
• Daniel Scott Schulz

Assignees

• OPTICAL ENGINES, INC.

Dates

Publication Date

20260505

Application Date

20220114

Claims (20)

1. 1 . A fiber support assembly, comprising: a first glass tube, wherein the first glass tube is attached to a microlens or lenslet of a microlens or lenslet array; a second glass tube at least partially disposed within the first glass tube; and a gain fiber disposed within the second glass tube, wherein the gain fiber has a first tapered end cap, and wherein the gain fiber with the first tapered end cap is aligned to the microlens or lenslet attached to the first glass tube; wherein the first tapered end cap has an outer diameter that increases from one end of the first tapered end cap to another end of the first tapered end cap, and wherein the first tapered end cap is configured to receive counter-pumping light.
2. 2 . The fiber support assembly according to claim 1 , further comprising: a third glass tube disposed between the first glass tube and the second glass tube.
3. 3 . The fiber support assembly according to claim 1 , further comprising: a pump fiber disposed within the second glass tube, wherein the pump fiber has a second tapered end cap; and a reflector configured to receive the counter-pumping light from the pump fiber and direct the counter-pumping light to the first tapered end cap of the gain fiber.
4. 4 . The fiber support assembly according to claim 3 , wherein the reflector is a dichroic mirror.
5. 5 . The fiber support assembly according to claim 1 , wherein the gain fiber is adjustable for alignment based on movement of the second glass tube relative to the first glass tube.
6. 6 . The fiber support assembly according to claim 5 , wherein the gain fiber is configured to be aligned to the microlens or lenslet using an alignment station with a camera.
7. 7 . A system, comprising: a microlens or lenslet array; and a plurality of fiber support assemblies, wherein each fiber support assembly of the plurality of fiber support assemblies comprises: a first glass tube, wherein the first glass tube is attached to a respective microlens or lenslet of the microlens or lenslet array; a second glass tube at least partially disposed within the first glass tube; and a gain fiber disposed within the second glass tube, wherein the gain fiber has a first tapered end cap, and wherein the gain fiber with the first tapered end cap is aligned to the respective microlens or lenslet attached to the first glass tube.
8. 8 . The system according to claim 7 , wherein each fiber support assembly of the plurality of fiber support assemblies further comprises: a pump fiber disposed within the second glass tube, wherein the pump fiber has a second tapered end cap; and a reflector configured to receive counter-pumping light from the pump fiber and direct the counter-pumping light to the first tapered end cap of the gain fiber.
9. 9 . The system according to claim 7 , further comprising: a respective seed or source, a respective amplifier front end, and one or more respective mode adapters connected to a respective gain fiber.
10. 10 . The system according to claim 7 , further comprising: a respective counter-pumping source connected to a respective pump fiber.
11. 11 . The system according to claim 7 , wherein the plurality of fiber support assemblies are disposed in a triangular array.
12. 12 . The system according to claim 11 , further comprising: a v-groove support structure configured to hold the triangular array of fiber support assemblies.
13. 13 . The system according to claim 7 , wherein the plurality of fiber support assemblies are disposed in a hexagonal array or a square array.
14. 14 . The system according to claim 7 , wherein the plurality of fiber support assemblies are stacked on one another to form an aligned array of fiber support assemblies.
15. 15 . A fiber support assembly, comprising: a first glass tube, wherein the first glass tube is attached to a microlens or lenslet of a microlens or lenslet array; a second glass tube at least partially disposed within the first glass tube; and a gain fiber disposed within the second glass tube, wherein the gain fiber has a first tapered end cap, and wherein the gain fiber with the first tapered end cap is aligned to the microlens or lenslet attached to the first glass tube; wherein the fiber support assembly further comprises: a pump fiber disposed within the second glass tube, wherein the pump fiber has a second tapered end cap; and a reflector configured to receive counter-pumping light from the pump fiber and direct the counter-pumping light to the first tapered end cap of the gain fiber.
16. 16 . The fiber support assembly according to claim 15 , further comprising: a third glass tube disposed between the first glass tube and the second glass tube.
17. 17 . The fiber support assembly according to claim 15 , wherein the reflector is a dichroic mirror.
18. 18 . The fiber support assembly according to claim 15 , wherein the gain fiber is adjustable for alignment based on movement of the second glass tube relative to the first glass tube.
19. 19 . The fiber support assembly according to claim 18 , wherein the gain fiber is configured to be aligned to the microlens or lenslet using an alignment station with a camera.
20. 20 . The fiber support assembly according to claim 15 , wherein the first tapered end cap has an outer diameter that increases from one end of the first tapered end cap to another end of the first tapered end cap, and wherein the first tapered end cap is configured to receive the counter-pumping light.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of International Patent Application No. PCT/US2020/020170, filed on Feb. 27, 2020, which claims the benefit of U.S. patent application Ser. No. 16/513,191, filed on Jul. 16, 2019. This application is also a continuation-in-part of U.S. patent application Ser. No. 16/513,191, filed on Jul. 16, 2019, which claims the benefit of U.S. Provisional Application No. 62/698,489, filed on Jul. 16, 2018, and U.S. Provisional Application No. 62/794,257, filed on Jan. 18, 2019. This application also claims the benefit of U.S. Provisional Application No. 63/183,892, filed on May 4, 2021. The disclosures of all of the foregoing applications are hereby incorporated by reference in their entireties. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT This invention was made with Government support under contract SBIR Phase 2 Contract SC0015905 awarded by the Department of Energy. The Government has certain rights in this invention. BACKGROUND Fiber lasers are becoming increasingly deployed in industrial, scientific, medical, and defense applications due to their high efficiency, robust and reliable construction, and their relatively low system size and weight. Pulsed fiber lasers, such as ultrafast fiber lasers, are of interest. Furthermore, pulsed fiber lasers can create femtosecond (fs) level pulses in small, rugged and reliable packages. Fiber nonlinearities, such as stimulated Brillouin scattering (SBS), Raman scattering, and self-phase modulation (SPM), act as impediments to realizing higher peak powers and even shorter pulse widths. SUMMARY In an exemplary embodiment, the present disclosure provides a fiber optic assembly. The fiber optic assembly includes: a gain fiber configured to output signal light; a first taper corresponding to the gain fiber, wherein the first taper is configured to expand the signal light output by the gain fiber; and a reflector configured to receive counter-pumping light and direct the counter-pumping light into the first taper. The first taper is further configured to receive the counter-pumping light and focus the counter-pumping light as the counter-pumping light propagates towards the gain fiber. In a further exemplary embodiment, the reflector is disposed relative to the first taper such that the reflector does not impede the expanded signal light output from the first taper. In a further exemplary embodiment, the fiber optic assembly further includes a pump fiber and a second taper corresponding to the pump fiber for carrying the counter-pumping light to the reflector. In a further exemplary embodiment, the fiber optic assembly further includes a support structure having a first groove or channel for holding the gain fiber and the first taper and a second groove or channel for holding the reflector. In a further exemplary embodiment, the reflector is part of a dichroic beam splitter assembly and comprises a dichroic coating for reflecting the counter-pumping light and passing the signal light. In a further exemplary embodiment, the gain fiber is spliced to the first taper. In a further exemplary embodiment, the first taper is a tapered fiber or a tapered glass rod. In a further exemplary embodiment, a first end of the first taper interfacing with the gain fiber has a first diameter corresponding to a cladding diameter of the gain fiber, and a second end of the first taper interfacing with the reflector has a second diameter larger than the first diameter. In a further exemplary embodiment, the first taper comprises: a first section having a diameter which increases from a first value to a second value over the length of the first section; and a second section having a constant diameter. In a further exemplary embodiment, the fiber optic assembly further includes an antireflective coating at an interface between the first taper and the reflector. In a further exemplary embodiment, the gain fiber is a large mode area (LMA) fiber or a photonic crystal fiber (PCF). In a further exemplary embodiment, the gain fiber is a composite fiber comprising a photonic crystal fiber (PCF) and a large mode area (LMA) fiber with a mode adapter interfacing the PCF fiber to the LMA fiber. In another exemplary embodiment, the present disclosure provides a fiber amplifier system. The fiber amplifier system includes: an amplifier front end configured to pre-amplify light from a seed source and output the pre-amplified light to a first section of gain fiber; a first mode adapter configured to connect the first section of gain fiber to a second section of gain fiber; a laser diode pump for providing counter-pumping light through a pump fiber; and a reflector assembly for directing the counter-pumping light from the pump fiber towards the first and second sections of gain fiber. In a further exemplary embodiment, the reflector assembly comprises a first taper, a reflector, and a second taper. In a further exemplary em