Fiber laser output head comprising a pump stripping and mode filtering function and method of making the same

Abstract

This invention discloses a fiber laser output head including pump stripping and mode filtering functions, comprising a metal base, a metal top cover, a pigtail, an output cap, and a thermally conductive substrate. The metal base and metal top cover form a space for placing the pigtail and the output cap. The pigtail passes through a pigtail hole and is fused to the output cap. A UV optical adhesive is applied to the coating layer of the pigtail near the pigtail hole. On the pigtail, a bare fiber etched area and a bare fiber adhesive application area are sequentially arranged towards the output cap. A thermally conductive substrate is provided below the bare fiber adhesive application area. High-refractive-index UV optical adhesive is filled between the bare fiber adhesive application area and the thermally conductive substrate, and the UV optical adhesive is used to fix the thin cylindrical side of the output cap. This invention also provides a method for manufacturing the aforementioned fiber laser output head including pump stripping and mode filtering functions. This invention can shorten the pigtail length between the CPS and the output head, reduce the laser volume, and make the optical axes of the pigtail and the output head lie in the same horizontal plane.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic device technology, specifically relating to a fiber laser output head that includes pump stripping and mode filtering functions and its manufacturing method. Background Technology

[0002] Currently, in most fiber lasers, the suspended device pigtail located between the pump stripper (CPS) after the gain fiber and the output head or collimator is quite long, occupying a large volume within the laser. Furthermore, the pigtail output by the pump stripper is usually not mounted at the same horizontal plane as the optical axis of the output head. This can easily cause various nonlinear effects, including amplified spontaneous emission (ASE), self-phase modulation (SPM), and stimulated Raman scattering (SRS), in high-power and ultrafast laser applications. It can also easily subject the suspended pigtail to external disturbances such as stress changes, causing many adverse effects on the output characteristics of fiber lasers, such as power, pulse width, spectral width, and beam quality. Summary of the Invention

[0003] The purpose of this invention is to provide a fiber laser output head and its manufacturing method that includes pump stripping and mode filtering functions. This fiber laser output head and its manufacturing method can shorten the length of the suspended device pigtail between the pump stripper (CPS) and the output head or collimator, thereby reducing the size of the laser. The device pigtail is integrated with the output end cap, so that the installation height of the output pigtail and the optical axis of the output head are in the same horizontal plane.

[0004] The technical solution adopted in this invention is:

[0005] A fiber laser output head that includes pump stripping and mode filtering functions includes a metal base, a metal top cover, a pigtail, an output end cap, and a thermally conductive substrate.

[0006] The metal base and metal cover form a space for placing the pigtail and the output cap, and the pigtail and the output cap are both placed on the metal base; a pigtail hole is provided at one end of the space, and the output cap is placed at the other end of the space; the pigtail passes through the pigtail hole and is fused to the thin post of the output cap; the fiber core of the pigtail and the optical axis of the output cap are located on the same horizontal plane.

[0007] The coating of the pigtail near the pigtail hole is provided with UV optical adhesive for fixing;

[0008] On the pigtail, a bare fiber etching area and a bare fiber dispensing area are sequentially provided towards the output end cap; a thermally conductive substrate is provided under the bare fiber dispensing area, and high-refractive-index ultraviolet optical adhesive is filled between the bare fiber dispensing area and the thermally conductive substrate.

[0009] Use UV optical adhesive to fix the thin cylindrical side of the output end cap.

[0010] A further proposed solution is that the output cap is a quartz rod with a step radius in the axial direction, with both end faces coated according to the laser wavelength. The thin cylindrical end face of the output cap is fused to the pigtail, and the thick cylindrical end face of the output cap emits laser light.

[0011] A further approach is to use a first-stage pump to strip the bare fiber corrosion area, destroying the cladding waveguide structure through chemical corrosion, with heat dissipation absorbed by the metal base and metal cover.

[0012] A further approach is to use chemical etchants to corrode the bare fiber areas.

[0013] A further alternative is that the chemical corrosive agent is hydrofluoric acid or abrasive paste.

[0014] A further approach is to use sapphire or glass wafers as the thermally conductive substrate.

[0015] A further proposed solution is to place the fiber optic port on the metal top cover and place the thermally conductive substrate in the groove of the metal base.

[0016] The metal base has grooves for fitting the output cap and the thermally conductive substrate, as well as screw holes for fitting the metal top cover, for positioning.

[0017] The present invention also provides a method for manufacturing the above-mentioned fiber laser output head including pump stripping and mode filtering functions, the method comprising the following steps:

[0018] S1: After passing the pigtail through the pigtail hole, fuse it to the output cap;

[0019] S2: Apply abrasive paste to the bare fiber etched area to perform fiber cladding etching, so that the pigtail has a bare fiber etched area and a bare fiber adhesive area in sequence from the output end cap direction.

[0020] S3: Install a thermally conductive substrate on a metal base;

[0021] S4: Install the output cap and pigtail that have been etched in step S2 onto the metal base, and fix the coating of the pigtail and the thin cylindrical side of the output cap near the pigtail hole with UV optical adhesive.

[0022] S5: Fill the area between the bare fiber dispensing area and the thermally conductive substrate with high refractive index UV optical adhesive;

[0023] S6: Cover with the metal top cover, lock it in place using the fixing screw holes, and seal and fix the pigtail hole with optical glue.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention can shorten the length of the passive device pigtail located after the gain fiber, reduce the nonlinear effects and external disturbances caused by it, and improve the degradation of the output characteristics of the fiber laser, such as power, pulse width, spectral width, and beam quality. At the same time, it shortens the device length in space, which is beneficial to improving the space utilization inside the fiber laser and further facilitates the miniaturization of the laser.

[0026] The fiber optic pigtail is used to transmit the laser beam; the output cap is used to emit the laser beam.

[0027] The bare fiber etched area is used for the first-stage pump stripping. By chemically etching and destroying the cladding waveguide structure, most of the cladding pump light and higher-order modes are scattered and leaked, and the heat is absorbed and dissipated by the metal base and metal cover.

[0028] The bare fiber dispensing area is used for the second-stage pump stripping. High-refractive-index ultraviolet optical adhesive is used to disrupt the refractive index gradient of the waveguide, further causing the remaining cladding pump light to scatter and leak into the higher-order mode adhesive, thereby improving stripping efficiency and optimizing beam quality.

[0029] High-refractive-index ultraviolet optical adhesive is filled between the bare fiber dispensing area and the thermally conductive substrate, utilizing the good light transmittance and thermal conductivity of the thermally conductive substrate to reduce the heat dissipation pressure of the adhesive.

[0030] The thermally conductive substrate is used for heat dissipation during the second-stage pump stripping, reducing the risk of poor thermal conductivity of high-refractive-index UV optical adhesives;

[0031] By improving the cladding pump stripping process and using a combined stripping method of chemical etching and optical adhesive, the stripping efficiency of existing traditional CPS products has been improved.

[0032] Integrating the output cap with the pigtail shortens the length of the passive fiber after the gain fiber, achieving nonlinear effect suppression and disturbance suppression, which can improve the degradation of output characteristics of fiber lasers such as power, pulse width, spectral width, and beam quality caused by this.

[0033] Compared with traditional discrete devices, this invention has advantages such as high stripping efficiency and compact optical path structure, and can be used in fields such as laser miniaturization.

[0034] By packaging the CPS and the output cap at the same height and close proximity, nonlinear effects and disturbances in fiber laser output are suppressed. Attached Figure Description

[0035] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0036] Figure 1 This is a schematic cross-sectional view of the fiber laser output head that includes pump stripping and mode filtering functions;

[0037] Figure 2 This is a top view of the packaged fiber laser output head that includes pump stripping and mode filtering functions;

[0038] In the diagram: 1. Fiber optic pigtail; 2. Output cap; 3. Bare fiber etched area; 4. Metal base; 5. Thermally conductive substrate; 6. UV optical adhesive for fixing; 7. High refractive index UV optical adhesive; 8. Bare fiber dispensing area; 9. Metal top cover; 10. Fixing screw hole; 11. Fiber optic pigtail hole. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] See Figure 1 and Figure 2 A fiber laser output head incorporating pump stripping and mode filtering functions includes a metal base 4, a metal top cover 9, a pigtail 1, an output cap 2, and a thermally conductive substrate 5. Both the metal base 4 and the metal top cover 9 have fixing screw holes 10 and are fixed with bolts, forming a space for placing the pigtail 1 and the output cap 2. The pigtail 1 and the output cap 2 are both placed on the metal base 4; a pigtail hole 11 is provided at one end of the space (on the metal top cover 9), and the output cap 2 is placed at the other end of the space (the output cap 2 is placed in a groove on the metal base 4); the pigtail 1 passes through the pigtail hole 11 and is fused to the thin post of the output cap 2; the fiber core of the pigtail 1 and the optical axis of the output cap 2 are located on the same horizontal plane. The coating of the pigtail 1 near the pigtail hole 11 is coated with UV optical adhesive 6 for fixing; on the pigtail 1, a bare fiber etching area 3 and a bare fiber dispensing area 8 are arranged sequentially towards the output cap 2; a thermally conductive substrate 5 is provided under the bare fiber dispensing area 8, and the thermally conductive substrate 5 is placed on a groove in the metal base 4; high refractive index UV optical adhesive 7 is filled between the bare fiber dispensing area 8 and the thermally conductive substrate 5. The thin column of the output cap 2 is fixed with UV optical adhesive 6.

[0041] The output cap 2 is a quartz rod with a step radius in the axial direction. Both end faces are coated according to the laser wavelength. The thin cylindrical end face of the output cap 2 is fused to the fiber optic tail, while the thick cylindrical end face of the output cap emits the laser. The bare fiber etching region 3 is removed using a first-stage pump stripping process, which chemically etches away the cladding waveguide structure. Heat dissipation is absorbed by the metal base 4 and the metal top cover 9. The bare fiber etching region 3 is etched using chemical etchants such as hydrofluoric acid or abrasive paste. The thermally conductive substrate 5 is a sapphire or glass wafer.

[0042] Specific examples:

[0043] The fiber laser output head is a 1064nm fiber laser output head. Pigtail 1 is a Nufern 25 / 250 passive fiber. The output cap 2 has a thin cylindrical section with a diameter of 1mm and a length of 5mm; a thick cylindrical section with a diameter of 2mm and a length of 5mm; both end faces are coated with a 1064nm antireflection film. The bare fiber etching area is 40mm long, with an etching time of 35 minutes, and is cleaned with deionized water. The metal base 4 is an aluminum alloy base. The thermally conductive substrate 5 is a sapphire thermally conductive substrate. The bare fiber dispensing area 8 has a dispensing area length of 20mm. The fixing UV optical adhesive 6 is DSMDF0016. The high-refractive-index UV optical adhesive 7 is NOA83H.

[0044] A method for manufacturing the above-mentioned 1064nm fiber laser output head including pump stripping and mode filtering functions, the method comprising the following steps:

[0045] S1: Pass the pigtail 1, which contains a bare fiber section of appropriate length, through the pigtail hole 11 and then fuse it with the output cap 2.

[0046] S2: Apply ArmourEtch abrasive paste to pigtail 1 to perform fiber cladding etching, so that on pigtail 1, there are bare fiber etching area 3 and bare fiber adhesive area 8 in sequence towards the output cap 2.

[0047] S3: Install a thermally conductive substrate 5 on the metal base 4;

[0048] S4: Install the output cap 2 and the pigtail 1, which have been etched in step S2, onto the metal base 4, and fix the coating layer of the pigtail 1 and the thin cylindrical side of the output cap 2 near the pigtail hole 11 with UV optical adhesive 6.

[0049] S5: Fill the area between the bare fiber dispensing area 8 and the thermally conductive substrate 5 with high refractive index UV optical adhesive 7.

[0050] S6: Cover the metal top cover 9, lock it in place through the fixing screw hole 10, and seal and fix the pigtail hole 11 with optical glue.

[0051] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A fiber laser output head comprising pump stripping and mode filtering functions, characterized in that: Includes a metal base, a metal top cover, a fiber optic cable, an output cap, and a thermally conductive substrate; The metal base and metal cover form a space for placing the pigtail and the output cap, and both the pigtail and the output cap are placed on the metal base; a pigtail hole is provided at one end of the space, and the output cap is placed at the other end of the space; the pigtail passes through the pigtail hole and is fused to the thin column of the output cap; the fiber core of the pigtail and the optical axis of the output cap are located on the same horizontal plane; the output cap is a quartz rod with a step radius in the axial direction, and the two end faces are coated according to the laser wavelength; the thin column end face of the output cap is fused to the pigtail, and the thick column end face of the output cap emits laser light; The coating of the pigtail near the pigtail hole is provided with UV optical adhesive for fixing; On the pigtail, a bare fiber etching area and a bare fiber adhesive dispensing area are sequentially provided towards the output end cap; a thermally conductive substrate is provided under the bare fiber adhesive dispensing area, and high-refractive-index ultraviolet optical adhesive is filled between the bare fiber adhesive dispensing area and the thermally conductive substrate; the bare fiber etching area is removed by a first-stage pump, which destroys the cladding waveguide structure through chemical etching, and the heat dissipation is absorbed by the metal base and the metal top cover. Use UV optical adhesive to fix the thin cylindrical side of the output end cap.

2. The fiber laser output head including pump stripping and mode filtering functions according to claim 1, characterized in that: The chemical etching process uses hydrofluoric acid or abrasive paste as the chemical etchant.

3. The fiber laser output head including pump stripping and mode filtering functions according to claim 1, characterized in that: The thermally conductive substrate is a sapphire or glass wafer.

4. The fiber laser output head including pump stripping and mode filtering functions according to claim 1, characterized in that: The fiber optic port is located on the metal top cover, and the thermally conductive substrate is placed in the groove of the metal base.

5. A method for manufacturing a fiber laser output head comprising pump stripping and mode filtering functions as described in any one of claims 1-4, characterized in that, Includes the following steps: S1: After passing the pigtail through the pigtail hole, fuse it to the output cap; S2: Apply abrasive paste to the bare fiber etched area to perform fiber cladding etching, so that the pigtail has a bare fiber etched area and a bare fiber adhesive area in sequence from the output end cap direction. S3: Install a thermally conductive substrate on a metal base; S4: Install the output cap and pigtail that have been etched in step S2 onto the metal base, and fix the coating of the pigtail and the thin cylindrical side of the output cap near the pigtail hole with UV optical adhesive. S5: Fill the area between the bare fiber dispensing area and the thermally conductive substrate with high refractive index UV optical adhesive; S6: Cover with the metal top cover, lock it in place using the fixing screw holes, and seal and fix the pigtail hole with optical glue.

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