Alternatively distributed thulium and holmium co-doped optical fiber
By designing alternating distributed co-doped thulium-holmium fibers, the problems of insufficient laser power and low conversion efficiency in existing thulium-holmium fiber lasers have been solved, achieving efficient laser conversion and stable transmission.
Patent Information
- Application Number
- CN202423101914.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-16
- Publication Date
- 2025-11-04
- Estimated Expiration
- 2034-12-16
AI Technical Summary
Existing 2.1μm thulium-holmium fiber lasers suffer from insufficient laser power, difficulty in amplification, and low conversion efficiency.
Alternating distributed co-doped thulium-holmium fiber is used. By alternately setting thulium-doped and holmium-doped fiber cores in the fiber core layer, energy transfer upconversion during thulium-holmium co-doping is avoided, thereby improving the conversion efficiency from 790nm pump light to 2.1μm laser.
This effectively avoids the impact of energy transfer upconversion, improves laser conversion efficiency, and enhances the transmission efficiency and stability of optical fibers.
Smart Images
Figure CN223514399U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of gain optical fiber, and more particularly to an alternating distributed co-doped thulium-holmium optical fiber. Background Technology
[0002] Due to their unique wavelength characteristics, 2.1μm holmium-doped fiber lasers have broad application prospects in biomedicine, lidar, space communication, plastics processing, and as efficient pump sources for mid- and far-infrared lasers. Holmium-doped fiber lasers are mainly implemented by co-pumping holmium-doped fibers with 1.9μm thulium-doped lasers or by using thulium-holmium co-doped fibers. Co-pumping holmium-doped fibers with 1.9μm thulium-doped lasers can significantly reduce quantum defect and improve laser slope efficiency and output power, but the laser system structure is complex and expensive. Furthermore, the low-refractive-index organic coating of the fiber has a significant absorption effect on the 1.9μm pump light, leading to severe heat load during high-power operation. Thulium-holmium co-doped fibers, through the energy transfer mechanism between thulium and holmium ions, allow holmium ions to indirectly absorb the 790nm pump light energy, which helps reduce the complexity of the laser system; however, under high-power operation, a conversion effect occurs, and the pump energy absorbed by the thulium ions is not fully transferred, ultimately resulting in low fiber efficiency. Therefore, finding a simple yet efficient solution is currently the challenge for holmium-doped lasers.
[0003] Therefore, there is an urgent need for an alternating distributed co-doped thulium-holmium optical fiber to solve the above-mentioned technical problems. Utility Model Content
[0004] The purpose of this invention is to provide an alternating distributed co-doped thulium-holmium fiber to improve the technical problems of insufficient laser power, difficulty in amplification, and low conversion efficiency in existing 2.1μm thulium-holmium fibers.
[0005] To solve the above technical problems, this utility model provides an alternating distributed co-doped thulium-holmium optical fiber, comprising a core layer, an inner cladding layer, an outer cladding layer, and a coating layer arranged sequentially from the inside to the outside along the radial direction, wherein the cross section of the core layer along the vertical radial direction is circular;
[0006] The fiber core layer includes several pairs of thulium-doped fiber cores and holmium-doped fiber cores, with the thulium-doped fiber cores and holmium-doped fiber cores arranged alternately along the vertical radial cross-section.
[0007] Preferably, the refractive index n1 of the thulium-doped fiber core is less than the refractive index n2 of the holmium-doped fiber core, and n2-n1<0.001.
[0008] Preferably, the refractive index n3 of the inner cladding is greater than the refractive index n4 of the outer cladding, and less than the refractive index n1 of the thulium-doped fiber core.
[0009] Preferably, the refractive index n5 of the coating layer is greater than the refractive index n2 of the holmium-doped fiber core.
[0010] Preferably, both the thulium-doped fiber core and the holmium-doped fiber core are fan-shaped.
[0011] Preferably, the number of thulium-doped fiber cores is the same as the number of holmium-doped fiber cores.
[0012] Preferably, the cross-sectional area of the thulium-doped fiber core is the same as that of the holmium-doped fiber core.
[0013] Preferably, both the thulium-doped fiber core and the holmium-doped fiber core include SiO2, GeO2, and Al2O3.
[0014] Preferably, the inner cladding layer has an octagonal cross-section along the vertical radial direction, while the outer cladding layer and the coating layer both have circular cross-sections along the vertical radial direction.
[0015] The beneficial effects of this invention are as follows: Unlike existing technologies, this invention provides an alternating distributed co-doped thulium-holmium fiber, the core layer of which includes several pairs of thulium-doped and holmium-doped cores, with the thulium-doped and holmium-doped cores arranged alternately along the vertical radial cross-section. Compared with conventional co-doping methods, the method of alternating doping with thulium and holmium ions can avoid the influence of energy transfer upconversion during thulium-holmium co-doping, thereby improving the conversion efficiency from 790nm pump light to 2.1μm laser. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the end face of the alternating distributed co-doped thulium-holmium optical fiber provided in Embodiment 1 of this utility model;
[0017] Figure 2 This is a schematic diagram of the end face of the alternating distributed co-doped thulium-holmium optical fiber provided in Embodiment 2 of this utility model;
[0018] In the attached diagram, 10 – core layer; 11 – thulium-doped core; 12 – holmium-doped core; 20 – inner cladding; 30 – outer cladding; 40 – coating layer. Detailed Implementation
[0019] The technical solutions of this utility model will be clearly and completely described below with reference to the embodiments of this utility model. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this utility model.
[0020] To address the technical problems of insufficient laser power, amplification difficulties, and low conversion efficiency in existing thulium-holmium optical fibers for 2.1 μm lasers, this invention provides an alternating distributed co-doped thulium-holmium optical fiber. This gain fiber achieves partitioned doping of thulium-holmium ions by controlling the structure of the core layer 10, avoiding energy transfer upconversion during thulium-holmium co-doping, thereby improving the conversion efficiency from 790 nm pump light to 2.1 μm laser.
[0021] Specifically, the technical solution of this application will now be described in conjunction with specific embodiments.
[0022] Example 1:
[0023] Please see Figure 1 , Figure 1 This is a schematic diagram of the end face of the alternating distributed co-doped thulium-holmium optical fiber provided in Embodiment 1 of this utility model; wherein, the alternating distributed co-doped thulium-holmium optical fiber includes a core layer 10, an inner cladding layer 20, an outer cladding layer 30 and a coating layer 40 arranged sequentially from the inside to the outside along the radial direction, the cross section of the core layer 10 along the vertical radial direction is circular; the core layer 10 includes a plurality of pairs of thulium-doped core parts 11 and holmium-doped core parts 12, the thulium-doped core parts 11 and holmium-doped core parts 12 are arranged alternately along the cross section along the vertical radial direction.
[0024] In Example 1, the thulium-doped fiber core 11 and the holmium-doped fiber core 12 are arranged alternately along the vertical radial section. Compared with the conventional co-doping method, the method of alternating doping of thulium and holmium ions can avoid the influence of energy transfer upconversion during thulium-holmium co-doping, thereby improving the conversion efficiency from 790nm pump light to 2.1μm laser.
[0025] Specifically, the mechanism by which alternating doping with thulium and holmium ions in different zones can avoid the effects of energy transfer upconversion during thulium-holmium co-doping is as follows:
[0026] Increased spatial distance: In partitioned alternating doping, thulium ions and holmium ions are spatially separated and no longer in close contact as in co-doping. This structure significantly increases the average distance between thulium and holmium ions. According to the energy transfer theory, the energy transfer probability is inversely proportional to the sixth power of the distance between ions. The increased distance leads to a significant decrease in the energy transfer probability, thereby effectively reducing the occurrence of energy transfer upconversion.
[0027] Reduced energy level matching: Energy transfer upconversion requires a good match between the emission energy level of the donor ion and the absorption energy level of the acceptor ion. During partitioned alternating doping, the coordination fields around thulium and holmium ions are different, causing their energy levels to shift. This makes it difficult to precisely match the photon energy emitted by thulium ions with the energy required for absorption by holmium ions, thus inhibiting the energy transfer upconversion process.
[0028] Energy transfer path obstructed: During co-doping, thulium ions and holmium ions are evenly distributed in the same region, forming a relatively direct energy transfer path, which makes energy transfer and upconversion easy. However, the partitioned alternating doping method disrupts this direct energy transfer path, requiring energy to cross different regions and media during the transfer process. This increases the difficulty and loss of energy transfer, reduces the energy reaching holmium ions and triggering upconversion, and thus avoids the impact of energy transfer and upconversion.
[0029] In Example 1, the refractive index n1 of the thulium-doped fiber core 11 is less than the refractive index n2 of the holmium-doped fiber core 12, and n2 - n1 < 0.001. The refractive index difference between the thulium-doped and holmium-doped fiber cores is extremely small to allow for a relatively smooth transition of light transmission between these two regions. This smaller refractive index difference allows light to more easily enter the holmium-doped fiber core 12 from the thulium-doped fiber core 11, maintaining good transmission continuity. This is beneficial for achieving complex light propagation processes throughout the entire fiber core region.
[0030] In Example 1, the refractive index n3 of the inner cladding 20 is greater than the refractive index n4 of the outer cladding 30, and less than the refractive index n1 of the thulium-doped fiber core 11; the refractive index n5 of the coating layer 40 is greater than the refractive index n2 of the holmium-doped fiber core 12. The relatively low refractive index of the inner cladding 20 creates a refractive index difference, reducing laser leakage from the fiber core to the cladding and improving light transmission efficiency and stability. The difference in refractive index between the inner cladding 20 and the outer cladding 30 also helps to further limit the propagation range of light, enhancing the fiber's ability to confine the pump light. The higher refractive index of the coating layer 40 compared to the holmium-doped fiber core 12 is typically used to protect the fiber and provide a certain mechanical strength, while also improving the fiber's heat resistance. The higher refractive index of the coating layer 40 reduces the impact of the external environment on light transmission, making the transmission of optical signals in the fiber more stable.
[0031] In Example 1, the cross-sections of the thulium-doped fiber core 11 and the holmium-doped fiber core 12 along the vertical radial direction are both fan-shaped, the cross-section of the inner cladding 20 along the vertical radial direction is octagonal, and the cross-sections of the outer cladding 30 and the coating layer 40 along the vertical radial direction are both circular. The shape and refractive index characteristics of the inner cladding 20 help control the propagation of light in the fiber core 10 and limit light leakage. The outer cladding 30 is circular, providing further support and protection for the internal structure. The outermost coating layer 40 is also circular, mainly serving to protect the optical fiber and reduce the influence of external factors on light transmission.
[0032] Furthermore, in Example 1, the cross section of the fiber core layer 10 along the vertical radial direction includes an alternately distributed thulium-doped fiber core portion 11 and a holmium-doped fiber core portion 12, both of which are semi-circular.
[0033] In Example 1, the number of thulium-doped fiber cores 11 is the same as the number of holmium-doped fiber cores 12, and the cross-sectional area of the thulium-doped fiber cores 11 is the same as the cross-sectional area of the holmium-doped fiber cores 12. This design helps to achieve a relatively balanced energy transfer and interaction between thulium ions and holmium ions, thus optimizing the overall optical properties.
[0034] In Example 1, the thulium doping concentration of the thulium-doped fiber core 11 is the same as the holmium doping concentration of the holmium-doped fiber core 12. This design ensures that the energy transfer between thulium ions and holmium ions is relatively balanced during light transmission and interaction, and that the energy transfer is not unbalanced due to the doping concentration of one ion being too high or too low.
[0035] In Example 1, the thulium-doped fiber core 11 includes Tm2O3, SiO2, GeO2 and Al2O3, and the holmium-doped fiber core 12 includes Ho2O3, SiO2, GeO2 and Al2O3; wherein, GeO2 is used to adjust the refractive index, and Al2O3 is used to dissolve rare earth ions.
[0036] Specifically, the method for fabricating alternating distributed co-doped thulium-holmium optical fibers provided in Example 1 is as follows:
[0037] Step 1: Prepare two high-purity quartz tubes with a length of 500 mm, an outer diameter of 25 mm, and a wall thickness of 3 mm as base tubes. At 2000℃, pass SF6 gas with a flow rate of 100 sccm to polish and etch the inner wall of the base tubes. Then, pass SiCl4 with a flow rate of 200 sccm, O2 with a flow rate of 200 sccm, and He with a flow rate of 100 sccm. Set the heating temperature to 1600℃ to promote the reaction of the mixed gas and deposit a porous SiO2 layer on the inner wall of the base tubes.
[0038] Step 2: Remove the substrate tube with the deposited loose layer and immerse it in a mixed solution of TmCl3 and AlCl3 rare earth ions and a mixed solution of HoCl3 and AlCl3 rare earth ions respectively. After immersion and doping for 1 hour, remove the substrate tube and then continuously introduce N2 at a flow rate of 1000 sccm into the tube for 0.5 hours to dry the moisture in the loose layer.
[0039] Step 3: Introduce 300 sccm of Cl2 into the base tube and set the heating temperature to 1000~1200℃ to dehydrate and dry the loose layer. Then, introduce 800 sccm of O2 and raise the temperature to 1300~1400℃ to oxidize the rare earth ions adsorbed in the loose layer. Finally, raise the temperature to 2000℃ to sinter the loose layer into a high-temperature vitrified core layer 10 doped with rare earth ions.
[0040] Step 4: The substrate tube is heated repeatedly at a high temperature of 2100℃ until it is melted and shrunk into thulium-doped fiber preform and holmium-doped fiber preform.
[0041] Step 5: Mechanically grind the thulium-doped fiber preform and the holmium-doped fiber preform into an octagon, and then cut them into two half-circles along the radial direction of the fiber core.
[0042] Step six: Alternately combine one half-circle thulium-doped unit with one half-circle holmium-doped unit to form a preform with a complete fiber core. Then, place it in a drawing tower and melt it into a fiber at a high temperature of 2000~2100℃ and coat it. The drawing speed is controlled at 5~20m / min, and finally, an alternating distributed co-doped thulium-holmium optical fiber is formed.
[0043] Example 2:
[0044] Please see Figure 2 , Figure 2 This is a schematic diagram of the end face of the alternating distributed co-doped thulium-holmium fiber provided in Embodiment 2 of this utility model; wherein, the alternating distributed co-doped thulium-holmium fiber includes a core layer 10, an inner cladding layer 20, an outer cladding layer 30 and a coating layer 40 arranged sequentially from the inside to the outside along the radial direction, the cross section of the core layer 10 along the vertical radial direction includes two alternately distributed thulium-doped fiber cores 11 and two holmium-doped fiber cores 12, and the cross section of the thulium-doped fiber cores 11 and the holmium-doped fiber cores 12 along the vertical radial direction is a quarter circle.
[0045] Specifically, the method for fabricating alternating distributed co-doped thulium-holmium optical fibers provided in Example 2 is as follows:
[0046] Step 1: Prepare two high-purity quartz tubes with a length of 500 mm, an outer diameter of 25 mm, and a wall thickness of 3 mm as base tubes. At 2000℃, pass SF6 gas with a flow rate of 100 sccm to polish and etch the inner wall of the base tubes. Then, pass SiCl4 with a flow rate of 200 sccm, O2 with a flow rate of 200 sccm, and He with a flow rate of 100 sccm. Set the heating temperature to 1600℃ to promote the reaction of the mixed gas and deposit a porous SiO2 layer on the inner wall of the base tubes.
[0047] Step 2: Remove the substrate tube with the deposited loose layer and immerse it in a mixed solution of TmCl3 and AlCl3 rare earth ions and a mixed solution of HoCl3 and AlCl3 rare earth ions respectively. After immersion and doping for 1 hour, remove the substrate tube and then continuously introduce N2 at a flow rate of 1000 sccm into the tube for 0.5 hours to dry the moisture in the loose layer.
[0048] Step 3: Introduce 300 sccm of Cl2 into the base tube and set the heating temperature to 1000~1200℃ to dehydrate and dry the loose layer. Then, introduce 800 sccm of O2 and raise the temperature to 1300~1400℃ to oxidize the rare earth ions adsorbed in the loose layer. Finally, raise the temperature to 2000℃ to sinter the loose layer into a high-temperature vitrified core layer 10 doped with rare earth ions.
[0049] Step 4: The substrate tube is heated repeatedly at a high temperature of 2100℃ until it is melted and shrunk into thulium-doped fiber preform and holmium-doped fiber preform.
[0050] Step 5: Mechanically grind the thulium-doped fiber preform and the holmium-doped fiber preform into an octagon, and then cut them into four quarter circles along the radial direction of the fiber core.
[0051] Step six: Two quarter-circle thulium-doped units and two quarter-circle holmium-doped units are alternately combined to form a preform with a complete fiber core. Then, it is placed in a drawing tower and melted into filaments at a high temperature of 2000-2100℃ and coated. The drawing speed is controlled at 5-20 m / min, and finally, alternating distributed co-doped thulium-holmium optical fiber is formed.
[0052] In summary, unlike existing technologies, this invention provides an alternating distributed co-doped thulium-holmium fiber. The core layer 10 has a circular cross-section along the vertical radial direction. The core layer 10 includes several pairs of thulium-doped core sections 11 and holmium-doped core sections 12, which are arranged alternately along the vertical radial direction. In Example 1, the thulium-doped core sections 11 and holmium-doped core sections 12 are arranged alternately along the vertical radial direction. Compared to conventional co-doping methods, the alternating partitioning of thulium and holmium ions avoids the influence of energy transfer upconversion during thulium-holmium co-doping, thereby improving the conversion efficiency from 790nm pump light to 2.1μm laser light.
[0053] It should be noted that all the above embodiments belong to the same utility model concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.
[0054] The above embodiments merely illustrate the implementation of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.
Claims
1. An alternating distributed co-doped thulium-holmium optical fiber, characterized in that, It includes a core layer, an inner cladding layer, an outer cladding layer, and a coating layer arranged sequentially from the inside to the outside along the radial direction, wherein the cross section of the core layer along the vertical radial direction is circular; The fiber core layer includes several pairs of thulium-doped fiber cores and holmium-doped fiber cores, with the thulium-doped fiber cores and the holmium-doped fiber cores arranged alternately along a cross section in the vertical radial direction.
2. The alternating distributed co-doped thulium-holmium optical fiber according to claim 1, characterized in that, The refractive index n1 of the thulium-doped fiber core is less than the refractive index n2 of the holmium-doped fiber core, and n2-n1<0.
001.
3. The alternating distributed co-doped thulium-holmium optical fiber according to claim 2, characterized in that, The refractive index n3 of the inner cladding is greater than the refractive index n4 of the outer cladding, and less than the refractive index n1 of the thulium-doped fiber core.
4. The alternating distributed co-doped thulium-holmium optical fiber according to claim 2, characterized in that, The refractive index n5 of the coating layer is greater than the refractive index n2 of the holmium-doped fiber core.
5. The alternating distributed co-doped thulium-holmium optical fiber according to claim 1, characterized in that, Both the thulium-doped fiber core and the holmium-doped fiber core are fan-shaped.
6. The alternating distributed co-doped thulium-holmium optical fiber according to claim 5, characterized in that, The number of thulium-doped fiber cores is the same as the number of holmium-doped fiber cores.
7. The alternating distributed co-doped thulium-holmium optical fiber according to claim 5, characterized in that, The cross-sectional area of the thulium-doped fiber core is the same as that of the holmium-doped fiber core.
8. The alternating distributed co-doped thulium-holmium optical fiber according to claim 1, characterized in that, Both the thulium-doped fiber core and the holmium-doped fiber core include SiO2, GeO2, and Al2O3.
9. The alternating distributed co-doped thulium-holmium optical fiber according to claim 1, characterized in that, The inner cladding layer has an octagonal cross-section along the vertical radial direction, while the outer cladding layer and the coating layer both have circular cross-sections along the vertical radial direction.