Optical amplifier cascade pumping recovery scheme of integrated 3D printing waveguide

Abstract

The invention discloses an optical amplifier cascade pumping recovery scheme integrated with a 3D printing waveguide, which is characterized by comprising the following steps of: fixing at least one section of rare earth doped optical fiber on the surface of an optical transparent waveguide substrate; the optical transparent substrate is made of quartz glass, a UV curing resin layer or other optical transparent materials; the area surrounding the rare-earth-doped optical fiber is filled with a light-curable colloid material, and a printable area tightly attached to the rare-earth-doped optical fiber is formed; according to the invention, the conical or gradient structure optical waveguide prepared by the 3D printing system can realize accurate coupling of the pump light and the rare earth-doped fiber cladding, and at the same time efficiently captures and guides the unabsorbed residual pump light; cascading recovery and closed-loop recovery paths are combined, the pumping utilization rate is greatly increased, energy waste is reduced, meanwhile, the power consumption power of the system is reduced, and therefore heat energy converted from residual pumping light is reduced, the heat management pressure in a high-power scene is relieved, and the design difficulty and cost of a heat dissipation module are reduced.

Description

Technical Field

[0001] This invention relates to the fields of optical fiber communication and laser technology, specifically to a cascaded pump recovery scheme for optical amplifiers integrating 3D-printed waveguides. Background Technology

[0002] Rare-earth-doped fiber amplifiers (such as EDFAs and YDFAs) are core components in optical communication networks, fiber optic sensing, and high-power laser systems. Their working principle involves using a pump laser to excite rare-earth-doped ions, causing energy level inversion and providing gain to the signal light. However, in traditional optical amplifiers, the utilization rate of the pump light is usually limited; a considerable portion of the pump energy is not absorbed and becomes residual pump light, ultimately dissipating as heat or leaking directly. This not only reduces the overall energy efficiency of the system and increases the difficulty and cost of thermal management, but also restricts further improvements in the performance of multi-stage cascaded amplifiers.

[0003] Currently, the main technical means to improve pump light utilization include bidirectional pumping and using fiber gratings (FBGs) to reflect residual pump light. However, these methods have drawbacks such as system complexity, high cost, poor flexibility, and low integration, making it difficult to achieve dynamic, flexible, and efficient redistribution of pump energy.

[0004] 3D printing of optical waveguides, especially laser direct writing technology based on processes such as two-photon polymerization, can flexibly construct low-loss optical waveguides of arbitrary shapes in three-dimensional space, providing new design freedom for integrated optical devices; however, there is currently no mature solution to combine this technology with pump energy recovery of fiber amplifiers to build a compact, efficient, and programmable pump energy management system.

[0005] To address this, a cascaded pump recovery scheme for optical amplifiers integrating 3D-printed waveguides was proposed. Summary of the Invention

[0006] The purpose of this invention is to propose a cascaded pump recovery scheme for optical amplifiers integrating 3D-printed waveguides in order to solve the above problems.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a cascaded pump recovery scheme for an optical amplifier integrating a 3D-printed waveguide, characterized by comprising the following steps: S1. Fiber fixation: At least one section of rare-earth-doped fiber is fixed to the surface of an optically transparent waveguide substrate; the optically transparent substrate is made of quartz glass, UV-cured resin layer or other optically transparent material; S2. Region Construction: A photocurable colloidal material is filled in the region surrounding the rare-earth-doped optical fiber to form a "printable region" that is tightly bonded to the rare-earth-doped optical fiber; S3. Waveguide fabrication: A 3D printing system is used to print a tapered or gradient optical waveguide in the "printable area"; the optical waveguide includes at least one input end for coupling input pump light and at least one output end for guiding unabsorbed pump light; S4. Pump light injection: The pump light generated by the pump laser is coupled into the cladding of the rare-earth-doped fiber through the input end of the optical waveguide; S5. Optical transmission and absorption: Pump light is transmitted in the cladding of rare-earth-doped optical fiber and absorbed by its core. S6. Residual light leakage: Unabsorbed residual pump light is discharged through an optical outlet provided on the rare earth-doped fiber; the optical outlet is provided in the tapered area at the tail of the rare earth-doped fiber or the window area on the sidewall of the rare earth-doped fiber. S7. Recycling and Reuse: The residual pump light that leaks out is captured by the output end of the optical waveguide and directionally guided, and then injected back into the pump input end of the next stage amplifier or fed back to the preamplifier, forming a cascaded recycling or closed-loop recycling path; at the same time, a control module is used to regulate the recycling process of the pump light; to achieve stable recycling of pump energy. S8. System Integration: The rare-earth-doped optical fiber, optical waveguide, and optically transparent waveguide substrate that have completed fixation, waveguide fabrication, and pump coupling are integrated and packaged into a 3D-printed waveguide optical amplifier.

[0008] Preferably, the pump laser has an output wavelength of 980nm, 1480nm, or 1550nm, supporting the coexistence of forward and reverse pumping structures.

[0009] Preferably, in step S7, the docking area between the optical waveguide output end and the optical outlet is provided with a buffer layer to reduce thermal stress and interface reflection. The buffer layer is made of thermosetting elastic optical adhesive or a polymer with matching refractive index.

[0010] Preferably, the input and output ends of the optical waveguide are constructed as optical waveguides with multiple intersecting cones or optical waveguides with a multi-level array structure.

[0011] Preferably, the rare-earth-doped optical fiber is a single-mode rare-earth-doped optical fiber, a multi-mode rare-earth-doped optical fiber, or a rare-earth-doped optical fiber with a double-clad structure.

[0012] Preferably, the photocurable colloidal material is a UV-curable resin, silicone, or flexible polymer, and its refractive index is higher than that of the rare-earth-doped fiber cladding and lower than that of the rare-earth-doped fiber core.

[0013] Preferably, the rare-earth-doped optical fiber is fixed to an optically transparent substrate by a mechanical support structure or a thermal adhesive layer.

[0014] Preferably, the control module is connected to a photodetector via a beam splitter to receive residual pump power feedback signals in real time, thereby adjusting the output power of the pump laser or switching the optical waveguide routing path to achieve balanced adjustment of the pump intensity at each output port of the optical waveguide, adapting to the consistency requirements of the subsequent amplifier for pump power and direction.

[0015] The beneficial effects of this invention are as follows: The tapered or gradient structure optical waveguides prepared by the 3D printing system can achieve precise coupling between pump light and rare earth-doped fiber cladding, while efficiently capturing and guiding unabsorbed residual pump light; combined with cascaded recovery and closed-loop recovery paths, the pump utilization rate is greatly improved, energy waste is reduced and the system power consumption is reduced, thereby reducing the heat energy converted from residual pump light, alleviating the thermal management pressure in high-power scenarios, and reducing the design difficulty and cost of heat dissipation modules; The optical waveguide path can be designed arbitrarily, supporting multiple working modes such as dynamic routing allocation, multi-point injection, cascade recovery, and closed-loop feedback, to adapt to complex system requirements. Attached Figure Description

[0016] Figure 1 This is a planar top view schematic diagram of the single-point control of the pump light path in this invention. Figure 2 This is a planar top view schematic diagram of multi-point control of the pump light path in this invention; Figure 3 This invention is a cascaded feedback topology diagram of a pump light 3D waveguide structure. Detailed Implementation

[0017] Below we combine Figures 1-3 The cascaded pump recovery scheme for optical amplifiers with integrated 3D printed waveguides described in this invention will be further explained.

[0018] It should be noted that all directional indications in the embodiments of the present invention, such as up, down, left, right, front, back, etc., are only used to explain the relative positional relationship and movement of the components in a specific posture as shown in the attached figure. If the specific posture changes, the directional indication will also change accordingly.

[0019] See appendix Figure 1 - Appendix Figure 3 As shown, an integrated 3D-printed waveguide optical amplifier cascade pump recovery scheme is presented. Example 1: Single-stage amplifier closed-loop pump recovery system First, a section of double-clad thulium-doped fiber is used as the gain medium and fixed to the surface of a UV resin substrate by a thermal adhesive layer. The thickness of the adhesive layer is controlled at 10~20μm to ensure that the fiber and the substrate are tightly bonded without significant stress.

[0020] Next, a high-refractive-index UV-curable resin is filled around the thulium-doped fiber to form a "printable area"; this area is pre-cured with UV light to ensure the resin is set; the refractive index of the UV-curable resin is greater than that of the thulium-doped fiber cladding but less than that of the fiber core to ensure pump light transmission efficiency.

[0021] Then, a laser direct-write 3D printing system is used to precisely print a tapered optical waveguide within the "printable area." This waveguide includes one input terminal and one output terminal. Simultaneously, a feedback branch is printed to form a closed-loop optical waveguide, constraining the pump light to propagate along the designed path and reducing transmission loss within the waveguide. Furthermore, the width of the input port is greater than that of the output port, adapting to the propagation characteristics of the corresponding wavelength pump light, improving the lateral or oblique pump coupling efficiency, and ensuring that the coupling loss meets the requirement of a total coupling loss of less than 1.5dB.

[0022] Subsequently, a 980nm wavelength pump laser with an input power of 500mW was selected. The pump light was coupled into the cladding of the thulium-doped fiber through the input end of the optical waveguide via a tapered multimode fiber; the coupling efficiency was 88%, and the actual injected power was 440mW.

[0023] The pump light propagates through the cladding of the optical fiber. During the transmission process, it is absorbed by thulium ions in the fiber, resulting in a signal gain of 300mW.

[0024] The residual pump light of 140mW is emitted from the optical outlet at the end of the fiber, with an emission efficiency of 92% and an actual emission of 128.8mW. The optical outlet is located in the tapered area or the side window area of ​​the thulium-doped fiber tail. The tapered area at the end of the fiber reduces the diameter of the tail to 1 / 3 to 1 / 2 of the original diameter through fiber tapering technology, with a tapering length of 3-5mm, so that the residual pump light is emitted due to mode mismatch. The side window area uses femtosecond laser etching or chemical etching to open windows with a diameter of 10-30μm on the side wall of the fiber. The window position avoids the main mode field region of the signal light (≥20μm away from the fiber core) to ensure that only the residual pump light is emitted.

[0025] The output end of the optical waveguide is connected to the optical outlet, and a thermosetting elastic optical adhesive or refractive index matching polymer is set in the docking area as a buffer layer to reduce thermal stress and interface reflection and improve coupling stability. The residual pump light that is leaked is fed back to the pump input end of the preamplifier through the feedback branch of the optical waveguide to form a closed loop recovery, realizing the recycling of residual pump light energy.

[0026] Meanwhile, during the pump injection process, the optical power of the amplifier is detected in real time by a photodetector and connected to the control module in the amplifier through a beam splitter. The control module dynamically adjusts the output power of the pump laser by receiving the feedback signal from the photodetector, so that the optical power generated by the pump laser is stabilized at 440±5mW, ensuring stable closed-loop recovery.

[0027] By integrating all components into a single package, the final pump utilization rate reaches 91%, and the system power consumption is reduced by 28%.

[0028] Example 2: Multi-stage amplifier cascaded pump recovery system Three segments of multimode thulium-doped optical fiber were selected and fixed to a UV-cured resin substrate by thermal bonding. Each segment was 5m long and the spacing between each segment was 20mm.

[0029] Silicone is filled around three segments of multimode rare-earth-doped optical fiber to form a 200μm thick "printable area", which is then thermosetting to form a quasi-waveguide structure. A multiphoton polymerization process was used to 3D print an array waveguide, which includes three input terminals connected to three 1550nm pump lasers, and three output terminals connected to three fiber sidewall windowed areas. Two cascaded waveguides were also printed to connect adjacent amplifiers.

[0030] Each fiber segment absorbs 600mW of pump power, generating signal gain, with a residual of 250mW. The residual pump light from the first segment is injected into the second segment via a cascaded waveguide, resulting in a total injection of 850 + 225 = 1075mW. The residual light from the second segment is then injected into the third segment, again resulting in a total injection of 850 + 225 = 1075mW. The control module adjusts the output power of the initial pump laser and distributes the residual pump light through power feedback, balancing the pump intensity at the output ports of each waveguide to ensure that the total injected power deviation of each segment is ≤3%.

[0031] With integrated packaging, the system pump utilization rate reaches 93%, and compared with a three-stage system without recovery, the total energy consumption is reduced by 32% and the heat dissipation cost is reduced by 40%.

[0032] The above embodiments are illustrative of the present invention and are not intended to limit the present invention. Any simple modifications to the present invention are within the scope of protection of the present invention.

Claims

1. An integrated 3D-printed waveguide optical amplifier stage cascaded pump recovery scheme, characterized in that, The method comprises the following steps: S1. Fiber fixing: fixing at least one section of rare earth doped fiber on the surface of an optically transparent waveguide substrate; the optically transparent substrate is made of quartz glass, a UV-cured resin layer, or other optically transparent materials; S2. Region building: filling a photo-curable gel material in the region surrounding the rare earth doped fiber to form a "printable region" closely adhering to the rare earth doped fiber; S3. Waveguide preparation: using a 3D printing system to print a tapered or gradient structured optical waveguide in the "printable region"; the optical waveguide comprises at least one input end for coupling input pump light and at least one output end for guiding unabsorbed pump light; S4. Pump light injection: coupling the pump light generated by a pump laser into the cladding layer of the rare earth doped fiber through the input end of the optical waveguide; S5. Light transmission and absorption: the pump light is transmitted in the cladding layer of the rare earth doped fiber and is partially absorbed by the core of the fiber; S6. Residual light leakage: the unabsorbed residual pump light is leaked out through the light leakage port provided on the rare earth doped fiber; the light leakage port is provided in the tail tapering region of the rare earth doped fiber or the windowed region of the sidewall of the fiber; S7. Recycling and reuse: the leaked residual pump light is captured by the output end of the optical waveguide and is directed to be injected again into the pump input end of the next stage amplifier or fed back to the previous stage amplifier, forming a stage recycling or closed loop recycling path; at the same time, a control module is used to regulate the reuse process of the pump light; realizing the stable recycling of the pump energy; S8. System integration: integrating the rare earth doped fiber, the optical waveguide, and the optically transparent waveguide substrate which have completed the fixing, waveguide preparation, and pump coupling to form a 3D printed waveguide optical amplifier.

2. The integrated 3D-printed waveguide optical amplifier stage cascaded pump recovery scheme according to claim 1, characterized in that: The pump laser has an output wavelength of 980 nm, 1480 nm, or 1550 nm, and supports the coexistence of forward and reverse pumping structures.

3. The integrated 3D-printed waveguide optical amplifier stage cascaded pump recovery scheme of claim 1, wherein In step S7, a buffer layer for reducing thermal stress and interface reflection is provided in the butt joint area of the output end of the optical waveguide and the light leakage port; the buffer layer is made of a heat-curable elastic optical glue or a refractive index matching polymer.

4. The integrated 3D-printed waveguide optical amplifier stage cascaded pump recovery scheme of claim 1, wherein The input end and the output end of the optical waveguide are constructed as a plurality of crossed taper optical waveguides or a multi-stage array structure optical waveguide.

5. The integrated 3D-printed waveguide optical amplifier stage cascaded pump recovery scheme of claim 1, wherein: The rare earth doped fiber is a single mode rare earth doped fiber, a multi-mode rare earth doped fiber, or a double-clad structure rare earth doped fiber.

6. The integrated 3D-printed waveguide optical amplifier stage cascaded pump recovery scheme of claim 1, wherein: The photo-curable gel material is a UV-cured resin, a silica gel, or a flexible polymer, which has a refractive index higher than that of the cladding layer of the rare earth doped fiber and lower than that of the core of the fiber.

7. The integrated 3D-printed waveguide optical amplifier cascade pump recovery scheme of claim 1, wherein: The rare earth doped fiber is fixed on the optically transparent substrate by a mechanical support structure or a thermal adhesive layer.

8. The integrated 3D printed waveguide, optical amplifier, stage-cascaded pump recovery scheme of claim 1, wherein: The control module is connected to a photodetector through a beam splitter to receive real-time residual pump light power feedback signals, and then adjust the output power of the pump laser or switch the optical waveguide routing path, so as to balance and adjust the pump intensity of each output port of the optical waveguide, and adapt to the consistency requirements of the pump power and direction of the next stage amplifier.

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