A method for preparing a soft glass optical fiber side pump coupler

Abstract

The preparation method of the soft glass fiber side pump coupler disclosed in the present invention comprises the following steps: taper the pump fiber into a long tapered structure; strip a certain length of the coating layer and the outer cladding of the middle section of the signal fiber, and the exposed inner cladding has the same components as the pump fiber; place the cone area and the cone waist of the pump fiber close to the exposed inner cladding to form a coupling area; heat the coupling area; cut off the pump fiber at one end of the self-coupling area, place the pump fiber and the signal fiber with the coupling area in a U-shaped substrate and fix them; sleeve the quartz glass tube on the outside of the U-shaped substrate and fix it, place it in the substrate of the packaging box, and finally fix the top cover on the substrate to complete the packaging. The method is simple and low in cost. The packaging structure of the prepared side pump coupler is stable, the carrying power is high, the insertion loss is low, the coupling efficiency is high, the performance is excellent, and the laser in the mid-infrared band can be effectively and stably output.

Description

Technical Field

[0001] The invention belongs to the field of preparation and packaging of optical devices, and in particular relates to a method for preparing a soft glass optical fiber side pump coupler. Background Art

[0002] Fiber lasers have been increasingly widely used in defense, medical and industrial processing fields due to their high efficiency, stability, low threshold, high beam quality and small size. Fiber couplers are one of the core components of fiber lasers. They can efficiently couple the optical energy of the laser to another optical fiber for transmission. They have a wide range of power, from microwatts to tens of watts or even hundreds of watts. Therefore, the improvement of pump coupling methods is a key technology. The commonly used pumping technologies are end pumping and side pumping. Compared with end pumping, side pumping has a larger pumping area and an unlimited number of pumping points. In theory, it is easier to achieve the coupling of high-power pumping light. Quartz-based side pump coupling technology is already quite mature, but there are significant physical differences between soft glass fiber and quartz fiber, so the development of soft glass fiber side pump couplers is relatively slow.

[0003] Soft glass optical fibers represented by fluoride glass optical fibers, tellurite glass optical fibers, and chalcogenide glass optical fibers have good transmittance in the mid-infrared band, especially 3 to 5 μm, but the application of soft glass optical fibers is limited by problems such as poor mechanical strength, narrow heating temperature range, and easy crystallization when heated. In 2018, Mitsubishi Diamond Corporation used the angle polishing method to prepare a fluoride fiber side pump coupler. However, since the angle polishing method requires the pump fiber to be polished to a certain angle and then fused to the signal fiber, it is challenging in the preparation of the coupler. In 2020, Laval University and others wrapped the tapered quartz fiber around the fluoride fiber to prepare a side pump coupler that does not require heating, and the coupling efficiency is as high as 92%. This preparation method is simple and effective, but because the pump fiber and the signal fiber are not fused together, there are problems with repeatability and long-term stability. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a soft glass optical fiber side-pump coupler in view of the shortcomings of the prior art. The preparation method is simple and has low preparation cost. The prepared side-pump coupler has a stable packaging structure, high carrying power, low insertion loss, high coupling efficiency, excellent performance, and can effectively and stably output lasers in the mid-infrared band.

[0005] The technical solution adopted by the present invention to solve the above technical problem is: a method for preparing a soft glass optical fiber side pump coupler, comprising the following steps:

[0006] S1. Take a soft glass fiber as a pump fiber, taper the pump fiber into a bilaterally symmetrical long tapered structure, and obtain a tapered area and a tapered waist in the middle of the pump fiber;

[0007] S2, taking a soft glass optical fiber as a signal optical fiber, stripping a certain length of the coating layer and the outer cladding of the middle section of the signal optical fiber to obtain a section of optical fiber with an exposed inner cladding, wherein the inner cladding has the same composition as the pump optical fiber;

[0008] S3, placing the cone region and cone waist of the pump fiber close to the exposed inner cladding of the signal fiber to form a coupling region;

[0009] S4, heating the coupling region by using a heating source, so that the pump optical fiber and the signal optical fiber in the coupling region are melted and form a certain fusion depth;

[0010] S5, cutting off the pump fiber at one end of the self-coupling region, placing the pump fiber and the signal fiber with the coupling region in the U-shaped substrate, and fixing the pump fiber and the signal fiber to the U-shaped substrate by dispensing glue;

[0011] S6. Sleeve the quartz glass tube on the outside of the U-shaped substrate, fix the quartz glass tube and the U-shaped substrate by dispensing glue, then place the quartz glass tube in the substrate of the packaging box, and finally fix the top cover on the substrate of the packaging box to complete the packaging.

[0012] Preferably, the pump fiber used in step S1 is a coreless fiber, and the signal fiber used in step S2 is a double-clad glass fiber consisting of a core, an inner cladding, an outer cladding, and a coating. The coreless fiber can reduce the end-face light energy density, reduce reflection, and prevent the fiber from being induced by high-power laser damage. In addition, the lack of cladding to bind the pump light is conducive to coupling the pump light from the pump fiber into the inner cladding of the signal fiber.

[0013] Preferably, in step S3, the cone region and cone waist of the pump optical fiber are attached in parallel or spirally wound to the exposed inner cladding of the signal optical fiber.

[0014] Furthermore, in step S3, alcohol or isopropyl alcohol is added between the cone region and cone waist of the pump fiber and the exposed inner cladding of the signal fiber to increase the adsorption force, ensure that the cone region and cone waist of the pump fiber are in full contact with the exposed inner cladding of the signal fiber, eliminate the gap, and ensure the attachment quality.

[0015] Preferably, the heating source used in step S4 is an Ω-type graphite filament, and the heating source is moved back and forth to heat the coupling area more than 4 times. The moving speed of the heating source is 0.5-0.8 mm / s, and the heating temperature of the heating source is 10-20°C higher than the taper temperature of the pump fiber. Inert gas protection is used during the heating process, and the flow rate of the inert gas is controlled at 300-500 mL / min. Since the soft glass fiber is very sensitive to temperature changes, the use of Ω-type graphite filaments for heating can achieve precise temperature control, heat the surroundings of the coupling area, and ensure that the fiber is heated evenly. At the same time, a lower heating temperature and inert gas protection are used. Multiple low-temperature heating can effectively suppress the problem of heat crystallization of the soft glass fiber. By increasing the number of back and forth heating of the Ω-type graphite filaments, it can be ensured that the pump fiber and the signal fiber have a certain fusion depth.

[0016] Preferably, the length of the U-shaped substrate is greater than the length of the quartz glass tube, the length of the quartz glass tube is greater than the exposed length of the inner cladding, and the exposed length of the inner cladding is greater than the total length of the cone region and the cone waist, so as to effectively protect the coupling area.

[0017] Preferably, in step S5 and step S6, the refractive indexes of the pump optical fiber and the inner cladding are both greater than the refractive index of the glue used for dispensing, so as to effectively protect the coupling region and avoid residual pump light.

[0018] Preferably, the quartz glass tube is provided with a plurality of air holes, which has good heat dissipation performance and can improve the carrying power of the side pump coupler. Furthermore, a heat dissipation channel is provided in the substrate of the packaging box to achieve a better heat dissipation effect.

[0019] In a preferred embodiment, the heat dissipation channel is a water-cooled heat dissipation channel, and the heat dissipation channel includes a water inlet and a water outlet. The water-cooled heat dissipation channel can be arranged in a U-shaped, circuitous, spiral, spiral circuitous, and other arrangements.

[0020] Compared with the prior art, the present invention has the following advantages: the pump fiber selected in the preparation method of the present invention has the same components as the inner cladding of the signal fiber, and the pump light can be coupled into the signal fiber to the maximum extent, and the pump fiber and the signal fiber form a certain fusion depth, and have a stable structure. The preparation method of the soft glass fiber side pump coupler of the present invention is simple, the preparation cost is low, and the packaging efficiency is high. It adopts a U-shaped substrate and a quartz glass tube to be packaged and fixed twice inside and outside, which can effectively protect the coupling area and ensure the packaging effect. The packaging structure of the prepared side pump coupler is stable, the carrying power is high, and it has low insertion loss, high coupling efficiency, excellent performance, and can effectively and stably output lasers in the mid-infrared band. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of a top view of the soft glass optical fiber side pump coupler prepared in Example 1 (the top cover of the packaging box is partially opened);

[0022] Figure 2 Schematic diagram of the pump optical fiber obtained by taper in step S1 of Example 1;

[0023] Figure 3 is a schematic diagram of the signal optical fiber with the inner cladding exposed obtained in step S2 of Example 1;

[0024] Figure 4 It is a schematic diagram of the attachment state of the tapered region and tapered waist of the pump optical fiber and the exposed inner cladding of the signal optical fiber in step S3 of Example 1;

[0025] Figure 5 Schematic diagram of the heating state of the Ω-shaped graphite filament to the coupling region C in step S4 of Example 1;

[0026] Figure 6 Schematic diagram of the fixing and glue dispensing positions of the U-shaped substrate and the optical fiber in step S5 of Example 1;

[0027] Figure 7 Schematic diagram of the fixing and glue dispensing positions of the quartz glass tube and the U-shaped substrate in step S6 of Example 1;

[0028] Figure 8 This is a schematic diagram of the effect of placing the quartz glass tube in the substrate of the packaging box in step S6 of Example 1;

[0029] Fig. 9 It is a schematic diagram of the attachment state of the tapered region and tapered waist of the pump optical fiber and the exposed inner cladding of the signal optical fiber in step S3 of Example 2;

[0030] The specific reference numerals in the figure are as follows:

[0031] 1-pump fiber, 11-taper region, 12-taper waist, 2-signal fiber, 21-core, 22-inner cladding, 23-coating layer, 3-heating source, 4-U-shaped substrate, 51-glue dispensing position, 52-glue dispensing position, 53-glue dispensing position, 6-quartz glass tube, 61-air vent, 7-cured UV glue, 8-substrate of packaging box, 81-water inlet, 82-water outlet, 9-top cover of packaging box, 10-screw hole. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with the embodiments of the drawings. The devices, components or methods not limited by the present invention all adopt conventional technical means in the art.

[0033] The method for preparing the soft glass optical fiber side pump coupler of Example 1 comprises the following steps:

[0034] S1. Take a soft glass fiber as the pump fiber 1. The pump fiber 1 is a coreless fiber. The pump fiber 1 is tapered into a bilaterally symmetrical long tapered structure, such as Figure 2 As shown, a cone region 11 and a cone waist 12 are obtained in the middle of the pump optical fiber 1, the length of the cone region 11 is greater than 20 mm, and the diameter of the cone waist 12 is less than 30 μm;

[0035] S2. Take a soft glass optical fiber as the signal optical fiber 2. The signal optical fiber 2 is a double-clad glass optical fiber consisting of a core 21, an inner cladding 22, an outer cladding (not shown in the figure) and a coating 23. Strip a certain length of the coating 23 and the outer cladding from the middle section of the signal optical fiber 2 to obtain a section of optical fiber with the inner cladding 22 exposed. Figure 3 As shown, the exposed length of the inner cladding 22 is greater than 40 mm, and the inner cladding 22 has the same composition as the pump fiber 1;

[0036] S3, attach the cone region 11 and the cone waist 12 of the pump optical fiber 1 to the exposed inner cladding 22 of the signal optical fiber 2 in parallel, as shown in FIG. Figure 4 As shown, alcohol is added between the two to increase the adsorption force, forming a coupling area C;

[0037] S4, using the heating source 3 to heat the coupling region C, so that the pump fiber 1 and the signal fiber 2 in the coupling region C are melted and form a certain fusion depth, the fusion depth is 0.005 times the sum of the diameters of the pump fiber and the signal fiber, wherein Figure 5 As shown, the heating source 3 used is an Ω-type graphite filament, and the heating source 3 is moved back and forth to heat the coupling area C more than 4 times. The moving speed of the heating source 3 is 0.5-0.8 mm / s. The heating temperature of the heating source 3 is 10-20°C higher than the taper temperature of the pump fiber 1. Inert gas protection is used during the heating process, and the flow rate of the inert gas is controlled at 300-500 mL / min.

[0038] S5, cut off the pump fiber 1 at one end of the self-coupling region C, place the pump fiber 1 with the coupling region C and the signal fiber 2 in the U-shaped substrate 4, and fix the pump fiber 1 and the signal fiber 2 to the U-shaped substrate 4 by dispensing glue, as shown in FIG. Figure 6 As shown, there are three glue-dispensing positions, the first glue-dispensing position 51 is at the end of the pump fiber 1 that is not tapered and the end of the adjacent signal fiber 2 that does not expose the inner cladding 22, the second glue-dispensing position 52 is at the coupling region C, and the third glue-dispensing position 53 is at the other end of the signal fiber 2 that does not expose the inner cladding 22;

[0039] S6, put the quartz glass tube 6 on the outside of the U-shaped substrate 4, as shown in Figure 7As shown, the two ends of the quartz glass tube 6 are fixed to the U-shaped substrate 4 by dispensing glue, and then the quartz glass tube 6 is placed in the substrate 8 of the aluminum packaging box, as shown in FIG. Figure 8 As shown, finally, the top cover 9 is fixed on the base plate 8 of the packaging box by screws (the base plate 8 and the top cover 9 of the packaging box are respectively provided with four screw holes 10 for fixing the screws), and the packaging is completed. The top view schematic diagram of the prepared soft glass fiber side pump coupler is shown in FIG. Figure 1 .

[0040] In Example 1, the soft glass optical fiber can be a fluoride glass optical fiber, a tellurite glass optical fiber or a chalcogenide glass optical fiber; the length of the U-shaped substrate 4 is greater than the length of the quartz glass tube 6, the length of the quartz glass tube 6 is greater than the exposed length of the inner cladding 22, and the exposed length of the inner cladding 22 is greater than the total length of the cone region 11 and the cone waist 12; in step S5 and step S6, the refractive index of the pump optical fiber 1 and the inner cladding 22 is greater than the refractive index of the glue used for dispensing, and the dispensing in Example 1 uses ultraviolet glue, Figure 1 and Figure 8 7 is the cured UV glue; a plurality of air holes 61 are provided on the quartz glass tube 6, a heat dissipation channel is provided in the substrate 8 of the packaging box, the heat dissipation channel is a water-cooled heat dissipation channel, the heat dissipation channel includes a water inlet 81 and a water outlet 82, and the water-cooled heat dissipation channel can be specifically arranged in a U-shaped, circuitous, spiral, spiral circuitous, and other arrangements.

[0041] The method for preparing the soft glass fiber side pump coupler of Example 2 is different from that of Example 1 in that, in step S3 of Example 2, the cone region 11 and the cone waist 12 of the pump fiber 1 are attached to the exposed inner cladding 22 of the signal fiber 2 by a spiral winding attachment method, and the attachment state diagram is shown in FIG. Fig. 9 .

Claims

1. A method for preparing a soft glass optical fiber side pump coupler, characterized in that: The following steps are involved: S1. Take a soft glass fiber as a pump fiber, taper the pump fiber into a bilaterally symmetrical long tapered structure, and obtain a tapered area and a tapered waist in the middle of the pump fiber; S2, taking a soft glass optical fiber as a signal optical fiber, stripping a certain length of the coating layer and the outer cladding of the middle section of the signal optical fiber to obtain a section of optical fiber with an exposed inner cladding, wherein the inner cladding has the same composition as the pump optical fiber; S3, placing the cone region and cone waist of the pump fiber close to the exposed inner cladding of the signal fiber to form a coupling region; S4, heating the coupling region by using a heating source, so that the pump optical fiber and the signal optical fiber in the coupling region are melted and form a certain fusion depth; S5, cutting off the pump fiber at one end of the self-coupling region, placing the pump fiber and the signal fiber with the coupling region in the U-shaped substrate, and fixing the pump fiber and the signal fiber to the U-shaped substrate by dispensing glue; S6, sleeve the quartz glass tube on the outside of the U-shaped substrate, fix the quartz glass tube and the U-shaped substrate by dispensing glue, then place the quartz glass tube in the substrate of the packaging box, and finally fix the top cover on the substrate of the packaging box to complete the packaging; The quartz glass tube is provided with a plurality of air holes, and the base plate of the packaging box is provided with a heat dissipation channel.

2. The method for preparing a soft glass fiber side pump coupler according to claim 1, characterized in that: The pump optical fiber used in step S1 is a coreless optical fiber, and the signal optical fiber used in step S2 is a double-clad glass optical fiber consisting of a core, an inner cladding, an outer cladding and a coating.

3. The method for preparing a soft glass fiber side pump coupler according to claim 1, characterized in that: In step S3, the cone region and cone waist of the pump optical fiber are attached to the exposed inner cladding of the signal optical fiber in parallel or spirally wound.

4. The method for preparing a soft glass fiber side pump coupler according to claim 3, characterized in that: In step S3, alcohol or isopropyl alcohol is dripped between the tapered region and tapered waist of the pump optical fiber and the exposed inner cladding of the signal optical fiber to increase the adsorption force.

5. The method for preparing a soft glass optical fiber side pump coupler according to claim 1, characterized in that: The heating source used in step S4 is an Ω-type graphite filament. The heating source is moved back and forth to heat the coupling area more than 4 times. The moving speed of the heating source is 0.5-0.8 mm / s. The heating temperature of the heating source is 10-20° C. higher than the taper temperature of the pump fiber. Inert gas protection is used during the heating process, and the flow rate of the inert gas is controlled at 300-500 mL / min.

6. The method for preparing a soft glass fiber side pump coupler according to claim 1, characterized in that: The length of the U-shaped substrate is greater than the length of the quartz glass tube, the length of the quartz glass tube is greater than the exposed length of the inner cladding, and the exposed length of the inner cladding is greater than the total length of the cone region and the cone waist.

7. The method for preparing a soft glass optical fiber side pump coupler according to claim 1, characterized in that: In step S5 and step S6, the refractive indexes of the pump optical fiber and the inner cladding are both greater than the refractive index of the glue used for dispensing.

8. The method for preparing a soft glass fiber side pump coupler according to claim 1, characterized in that: The heat dissipation channel is a water-cooled heat dissipation channel, and the heat dissipation channel includes a water inlet and a water outlet.

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