Array pulse fiber laser module

Abstract

According to the array pulse fiber laser module provided by the invention, a seed source adopts a VCSEL array, so that the VCSEL array can provide multiple paths of seed light and couple the seed light into a plurality of amplification sub-modules, the number of laser paths of the array pulse fiber laser module can be greatly increased, and the robustness of the array pulse fiber laser module can be greatly improved; and long-term working stability can be maintained. Meanwhile, the amplification sub-modules can be flexibly combined according to needs, so that the maximum amplification efficiency and output power are realized, and the overall power consumption of the array pulse fiber laser module is further reduced.

Description

Technical Field

[0001] The invention relates to the field of optical fiber laser technology, and in particular to an array pulse optical fiber laser module. Background Art

[0002] The rapid development of autonomous driving, intelligent transportation, low-altitude flight, surveying and mapping, etc., has put forward higher requirements for sensor devices such as LiDAR. Vehicle-mounted LiDAR mainly uses two bands of lasers, 905nm and 1550nm. Among them, 905nm has the characteristics of low cost and mature technology, and has become the main solution for vehicle-mounted LiDAR. However, the 905nm solution has the disadvantages of low human eye damage threshold, large divergence, and large atmospheric loss, which makes it difficult to apply to long-distance, high-precision, and densely populated area detection. The 1550nm fiber laser can effectively make up for the shortcomings of the 905nm laser, and has the advantages of low atmospheric attenuation, human eye safety, good beam quality, high resolution and long detection distance. However, the 1550nm fiber LiDAR is only equipped with 1 to 2 laser modules, and the low robustness poses a greater risk in work.

[0003] Therefore, there is an urgent need for an array pulse fiber laser module to solve the above technical problems. Summary of the invention

[0004] The object of the present invention is to provide an array pulse fiber laser module for improving the technical problem of low robustness of existing array pulse fiber laser modules.

[0005] In order to solve the above technical problems, the present invention provides an array pulse fiber laser module, which includes a VCSEL array, a microlens array and n amplifying submodules connected by optical signals in sequence from the signal input end to the signal output end, the VCSEL array includes n light-emitting points, the microlens array includes n microlenses, and n is a positive integer greater than 1; Each light-emitting point is coupled with an optical axis of a micro-lens, and each optical axis of the micro-lens is coupled with an input end of an amplifying sub-module.

[0006] Preferably, the working wavelength band of the signal light emitted by the light-emitting point includes any one of a 1um wavelength band, a 1.5um wavelength band and a 2um wavelength band.

[0007] Preferably, the arrangement shape of the plurality of light emitting points includes any one of a hexagonal shape, a rectangular shape and a honeycomb shape.

[0008] Preferably, the amplifier module is a forward pumping structure or a reverse pumping structure.

[0009] Preferably, the amplifier module comprises a first isolator, a beam combiner, a gain optical fiber and a second isolator which are sequentially connected from the signal input end to the signal output end; The first input end of the beam combiner is connected to the output end of the first isolator, the second input end of the beam combiner is connected to the pump source, and the output end of the beam combiner is connected to the gain optical fiber.

[0010] Preferably, the beam combiner is a wave combining device, and the beam combiner comprises a signal arm and a pump arm, the signal arm is used to transmit the signal light emitted by the light emitting point, and the pump arm is used to be fusion-coupled with the pump source.

[0011] Preferably, the pump source is a single-mode pump or a multi-mode pump.

[0012] Preferably, the pump source is a multi-mode pump with a pigtail, the wavelength of the pump source is 910-985 nm, and the power is 10 W.

[0013] Preferably, the first isolator and the second isolator are both unidirectional conductive devices, and the operating bands of the first isolator and the second isolator are both 1500-1600 nm.

[0014] Preferably, the gain optical fiber is an erbium-ytterbium co-doped optical fiber with a core diameter of 6-11 um and a cladding diameter of 122-132 um.

[0015] The beneficial effects of the present invention are as follows: Different from the prior art, the present invention provides an array pulse fiber laser module, which uses a VCSEL array as a seed source, so that the VCSEL array can provide multi-channel seed light and couple into multiple amplifier modules, which can greatly increase the number of laser channels and robustness of the array pulse fiber laser module, and is conducive to maintaining long-term working stability. At the same time, the amplifier modules can be flexibly combined as needed to achieve maximum amplification efficiency and output power, thereby reducing the overall power consumption of the array pulse fiber laser module. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of the overall structure of the array pulse fiber laser module provided in Example 1 of the present invention; Figure 2 Schematic diagram of the arrangement shape of the VCSEL array in the array pulse fiber laser module provided in Example 1 of the present invention; Figure 3 Schematic diagram of the arrangement shape of the VCSEL array in the array pulse fiber laser module provided in Example 2 of the present invention; In the attached figure: 100 - array pulse fiber laser module; 10 - VCSEL array; 11 - light emitting point; 20 - microlens array; 21 - microlens; 30 - amplifier module; 31 - first isolator; 32 - combiner; 33 - gain fiber; 34 - second isolator; 35 - pump source. DETAILED DESCRIPTION

[0017] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] The purpose of the present invention is to address the defects of the prior art. The purpose of the present invention is to provide an array pulse fiber laser module 100, which has the excellent characteristics of a 1.5um fiber laser radar, with only a small increase in the system volume, but greatly improved system robustness, and has potential use in phased array laser radars.

[0019] The technical solution of the present invention is now described in conjunction with specific embodiments.

[0020] Embodiment 1: See also Figure 1 , Figure 1 1 is a schematic diagram of the overall structure of the array pulse fiber laser module 100 provided in Example 1 of the present invention; Figure 2 1 is a schematic diagram of the arrangement shape of the VCSEL array 10 in the array pulse fiber laser module 100 provided in Example 1 of the present invention; wherein the array pulse fiber laser module 100 includes a VCSEL array 10, a microlens array 20 and n amplifying submodules 30 optically connected in sequence from the signal input end to the signal output end, the VCSEL array 10 includes n light-emitting points 11, the microlens array 20 includes n microlenses 21, and n is a positive integer greater than 1; Each light emitting point 11 is coupled to an optical axis of a micro lens 21 , and each optical axis of the micro lens 21 is coupled to an input end of an amplifying sub-module 30 .

[0021] In the first embodiment, the VCSEL array 10 includes 16 light-emitting points 11 , and the microlens array 20 includes 16 microlenses 21 .

[0022] In this embodiment 1, the VCSEL array 10 (Vertical Cavity Surface Emitting Laser) array includes n light-emitting points 11. The VCSEL array 10 itself has unique advantages. It emits lasers vertically to the substrate surface. Compared with traditional edge-emitting lasers, it is easy to realize two-dimensional array integration, can work at a lower driving current, and has better beam quality of the emitted light (generally a circular spot with a relatively small divergence angle). As the initial optical signal generating part of the entire array pulse fiber laser module 100, the VCSEL array 10 can output multiple optical signals with certain characteristics (such as specific wavelength, power, etc.), and is the source of subsequent optical signal processing and amplification.

[0023] In this embodiment 1, the working band of the signal light emitted by the light-emitting point 11 includes any one of the 1um band, the 1.5um band and the 2um band, preferably the 1.5um band. The 1.5um band laser can effectively make up for the shortcomings of the 905nm laser, and has the advantages of small atmospheric attenuation, eye safety, good beam quality, high resolution and long detection distance.

[0024] In the present embodiment 1, the arrangement shape of the plurality of light emitting points 11 includes any one of a hexagonal shape, a rectangular shape and a honeycomb shape, preferably a rectangular shape, such as Figure 2 shown.

[0025] In the present embodiment 1, the microlens array 20 includes 16 microlenses 21, and the optical axes of the multiple microlenses 21 are coupled one-to-one with the multiple light-emitting points 11 in the VCSEL array 10. This one-to-one coupling design ensures that the light emitted by each light-emitting point 11 can accurately enter the corresponding microlens 21. The microlens 21 here plays the role of converging, collimating or adjusting the beam parameters of the light. Since the light emitted by the light-emitting point 11 may have a certain degree of divergence, the divergent light can be appropriately shaped by the microlens 21 to make it more in line with the requirements of the subsequent amplification submodule 30 for the input light.

[0026] In this embodiment 1, the main function of the amplifier module 30 is to amplify the power of the input optical signal. In practical applications, the power of the optical signal initially generated by the VCSEL array 10 is often relatively low, and may not meet some application scenarios with long-distance transmission and high energy requirements. Through these amplifier modules 30, the power of the optical signal can be increased to the required level.

[0027] In the present embodiment 1, the amplifier module 30 is a forward pumping structure or a reverse pumping structure, preferably a forward pumping structure.

[0028] In this embodiment 1, the amplifier module 30 includes a first isolator 31, a beam combiner 32, a gain fiber 33 and a second isolator 34 which are sequentially connected from the signal input end to the signal output end; The first input end of the beam combiner 32 is connected to the output end of the first isolator 31 , the second input end of the beam combiner 32 is connected to the pump source 35 , and the output end of the beam combiner 32 is connected to the gain fiber 33 .

[0029] Specifically, the beam combiner 32 is a wave combining device, and the beam combiner 32 includes a signal arm and a pump arm, wherein the signal arm is used to transmit the signal light emitted by the light emitting point 11, and the pump arm is used to be fused and coupled with the pump source 35. Through such a structural design, the beam combiner 32 can effectively integrate light from different sources (signal light and pump light) and different functions, laying the foundation for the subsequent gain amplification process.

[0030] Specifically, the pump source 35 is a single-mode pump or a multi-mode pump.

[0031] In this embodiment 1, the pump source 35 is a multi-mode pump with a pigtail, the wavelength of the pump source 35 is 910-985nm, and the power is 10W; the advantage of the multi-mode pump is that it can carry relatively high optical power, which is suitable for use in scenarios where a large energy injection is required to achieve high-multiple amplification of the signal light. The pigtail design facilitates the fusion coupling with the pump arm of the combiner 32, and improves the stability and efficiency of the optical connection.

[0032] Specifically, the first isolator 31 and the second isolator 34 are both unidirectional conductive devices, and the operating bands of the first isolator 31 and the second isolator 34 are both 1500~1600nm; wherein, in the transmission path of the signal light, the first isolator 31 is located at the front end, and it can block the stray light or reflected light that may enter the amplifier module 30 from the outside in the reverse direction, so as to avoid the interference of these lights on the signal light and the possible adverse effects on the internal components (such as the gain fiber 33, etc.); the second isolator 34 is located at the rear end, and it can prevent the signal light amplified by the gain fiber 33 from being reflected when it is output, and avoid the reflected light from entering the gain fiber 33 and other components again, thereby ensuring that the signal light can be stably output in the expected direction, and maintaining the normal working order of the amplifier module 30 and even the entire array pulse fiber laser module 100.

[0033] Specifically, the gain fiber 33 is an erbium-ytterbium co-doped fiber, with a core diameter of 6-11um and a cladding diameter of 122-132um. This fiber achieves gain amplification of signal light in a specific band by doping erbium (Er) and ytterbium (Yb) elements in the core at the same time, using the energy level structure of the erbium element, while the ytterbium element plays a sensitizing role, which can more efficiently absorb the energy of the pump light and transfer it to the ytterbium element, thereby improving the overall amplification efficiency. The core diameter is 6-11um, and the relatively small core diameter helps to effectively constrain and conduct the optical signal, so that the light can be stably transmitted in the core through total reflection and other principles; the appropriate cladding size can provide good protection and optical environment for the core on the one hand, and on the other hand, it is also convenient for connection and adaptation with other optical fibers or optical components during production and use.

[0034] The specific working process of the array pulse fiber laser module 100 provided in Example 1 of the present invention is now further described in detail: The VCSEL array 10 in this embodiment 1 presents a rectangular 4×4 distribution, with a total of 16 light-emitting points 11. The microlens array 20 keeps the optical axis of each microlens 21 well aligned with each light-emitting point 11, and couples the signal light emitted by the VCSEL array 10 into the corresponding input end pigtail of the first isolator 31. At this time, the light-emitting points 11 of the VCSEL array 10, the microlenses 21 of the microlens array 20, and the pigtail of the first isolator 31 correspond one by one. The output end pigtail of the first isolator 31 is fused together with the input end of the combiner 32 to couple the 1.5um laser into the gain fiber 33. The pump source 35 is fused to the pump arm of the combiner 32 to couple the pump light into the gain fiber 33. The output end of the gain fiber 33 is fused to the pigtail of the second isolator 34. The pump light activates particles in the gain fiber 33 to achieve amplification of the 1.5um laser. The amplified laser light is outputted through the second isolator 34 , and the return light is prevented from interfering with the array pulse fiber laser module 100 .

[0035] Embodiment 2: See also Figure 3 , Figure 3 Schematic diagram of the arrangement shape of the VCSEL array 10 in the array pulse fiber laser module 100 provided in Example 2 of the present invention; the array pulse fiber laser module 100 provided in Example 2 of the present invention has substantially the same structure as the array pulse fiber laser module 100 provided in Example 1 of the present invention, and the only difference is that: The VCSEL array 10 in the array pulse fiber laser module 100 provided in the second embodiment presents a honeycomb distribution, with a total of 19 light-emitting points 11 .

[0036] Different from the prior art, the array pulse fiber laser module 100 provided by the present invention also has the following advantages: 1. The present invention uses the VCSEL array 10 as a seed light source to provide array output, thereby improving the robustness of the array pulse fiber laser module 100 without significantly increasing the volume of the seed light source.

[0037] 2. The VCSEL array 10 of the present invention serves as an amplified seed light source and does not play a pumping role itself.

[0038] 3. As a low-power laser, the common failure factor of 1.5um fiber laser in practical applications is the failure of the signal light source and the pump light source; the VCSEL array 10 of the present invention, as an optional signal light source, has the advantages of high integration and dense light-emitting points 11. It is foreseeable that even if individual light-emitting points 11 fail, it will not affect the operation of the array pulse fiber laser module 100, which is of great significance for vehicle-mounted laser radar.

[0039] 4. 1.5um fiber lasers have the advantages of eye safety, low atmospheric transmission loss, excellent beam quality, and high resolution, but compared with semiconductor lasers, they have the weaknesses of large size and insufficient robustness. This is because fiber lasers require corresponding drive and pump systems, so they are generally larger in size. At the same time, in a single-signal source single-output mode, if one light source fails, the on-board lidar will fail, which can easily threaten the safety of life and property of passengers. In general, in order to increase the robustness of the system, two or more light sources are arranged at the same time, causing the system volume to increase exponentially; the present invention uses the VCSEL array 10 as a seed light source, which can increase the number of output light paths while obtaining a smaller volume increase.

[0040] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For matters that are not described in detail in some embodiments, reference may be made to the description in other embodiments.

[0041] The above embodiments only express the implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An array pulse fiber laser module, characterized in that: A VCSEL array, a microlens array and n amplifying submodules connected in sequence by optical signals are included along the signal input end to the signal output end, the VCSEL array includes n light-emitting points, the microlens array includes n microlenses, and n is a positive integer greater than 1; Wherein, each of the light-emitting points is coupled with an optical axis of the microlens, and each of the optical axes of the microlens is coupled with an input end of the amplifying submodule.

2. The array pulse fiber laser module according to claim 1, characterized in that: The working wavelength band of the signal light emitted by the light-emitting point includes any one of a 1um wavelength band, a 1.5um wavelength band and a 2um wavelength band.

3. The array pulse fiber laser module according to claim 1, characterized in that: The arrangement shape of the plurality of light emitting points includes any one of a hexagonal shape, a rectangular shape and a honeycomb shape.

4. The array pulse fiber laser module according to claim 1, characterized in that: The amplifier module is a forward pumping structure or a reverse pumping structure.

5. The array pulse fiber laser module according to claim 1, characterized in that: The amplifier module includes a first isolator, a beam combiner, a gain optical fiber and a second isolator which are sequentially connected from the signal input end to the signal output end; The first input end of the beam combiner is connected to the output end of the first isolator, the second input end of the beam combiner is connected to a pump source, and the output end of the beam combiner is connected to the gain optical fiber.

6. The array pulse fiber laser module according to claim 1, characterized in that: The beam combiner is a wave combining device, and comprises a signal arm and a pump arm. The signal arm is used to transmit the signal light emitted by the light emitting point, and the pump arm is used to be fusion-coupled with the pump source.

7. The array pulse fiber laser module according to claim 1, characterized in that: The pump source is a single-mode pump or a multi-mode pump.

8. The array pulse fiber laser module according to claim 7, characterized in that: The pump source is a multi-mode pump with a pigtail, the wavelength of the pump source is 910-985nm, and the power is 10W.

9. The array pulse fiber laser module according to claim 1, characterized in that: The first isolator and the second isolator are both unidirectional conductive devices, and the operating bands of the first isolator and the second isolator are both 1500-1600 nm.

10. The array pulse fiber laser module according to claim 1, characterized in that: The gain optical fiber is an erbium-ytterbium co-doped optical fiber with a core diameter of 6-11um and a cladding diameter of 122-132um.

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