Output optical system of fiber laser

Abstract

The utility model discloses an output optical system of an optical fiber laser, which relates to the technical field of laser, and comprises an optical fiber, a first plane mirror, a collimating lens group and a focusing lens group which are sequentially arranged along the direction of an optical axis, the inclination angle is A, the numerical aperture of the light outlet of the optical fiber is NA, and the requirement that sinA is larger than or equal to 1 / 2 NA is met. According to the technical scheme provided by the utility model, the inclined first plane mirror is arranged, so that the laser in the optical fiber cannot be emitted into the light outlet of the optical fiber again after being reflected by the first plane mirror, thereby preventing high-power return light from damaging a laser amplifier, a resonant cavity and other optical devices, by limiting the relationship between the inclination angle and the numerical aperture, the inclination angle is matched with the numerical aperture, so that the reflected light can be ensured not to enter the optical fiber when facing light outlets with different numerical apertures, and the applicability of the system is improved.

Description

Technical Field

[0001] This utility model relates to the field of laser technology, and in particular to an output optical system for a fiber laser. Background Art

[0002] Fiber lasers generate a laser beam by absorbing pump light emitted from a semiconductor pump tube through a rare-earth-doped gain fiber. This light is then amplified by an FBG (Fiber Bragg Grating), undergoes multiple stages of amplification and multi-path coupling, and is output through a power transmission fiber via a QBH (Quasi-Brewster Angle High-power Fiber Coupler Output Cap). Compared to traditional solid-state lasers, fiber lasers offer advantages such as superior beam quality, high coherence, high brightness, high conversion efficiency, small size, and long lifespan. They are widely used in materials processing, including marking, drilling, welding, cutting, cleaning, and coating, as well as in optical communication, spectral imaging, and medical applications. In recent years, with advancements in semiconductor pump technology, improvements in large-mode-area double-clad fiber fabrication processes, and fiber combining technology, the output power of fiber lasers has been increasing at an astonishing rate. It is precisely this continuous improvement in the output and peak power of fiber lasers that has met the diverse needs of modern high-tech materials processing.

[0003] However, one problem currently faced in the processing of materials with fiber lasers is that when processing highly reflective materials, such as highly reflective metals like gold, silver, and copper, the laser output from the fiber laser may be reflected off the material surface and then re-enter the laser path. When this reflected light reaches the laser oscillation end, it will be gradually amplified, eventually causing irreversible damage to the fiber laser optical system and burning out the optical components.

[0004] The current solution to this problem in the fiber laser industry is to apply the laser output head to the working surface of the material at a certain angle when processing the material. In this way, most of the reflected laser will be transmitted along the angle direction and cannot enter the laser optical path. However, the drawback of this method is that some reflected light still returns to the laser optical path, causing damage to the laser. Utility Model Content

[0005] In view of the shortcomings of the existing technology, the main purpose of this utility model is to propose an output optical system for fiber lasers, which aims to solve the problem of reflected light returning to the laser optical path during the use of lasers, causing damage to the laser.

[0006] To achieve the above objectives, this utility model proposes an output optical system for a fiber laser, comprising an optical fiber, a first plane mirror, a collimating lens group, and a focusing lens group arranged sequentially along the optical axis. The first plane mirror is tilted relative to the optical axis at an angle of A, and the numerical aperture of the optical fiber's output port is NA, satisfying sinA ≥ 1 / 2NA.

[0007] In one embodiment, the collimating lens group includes a first lens with positive optical power, a second lens with negative optical power, and a third lens with positive optical power arranged sequentially along the optical axis.

[0008] In one embodiment, the first lens is a biconvex lens;

[0009] The second lens is a concave-convex lens, and its side facing the first lens is concave.

[0010] The third lens is a concave-convex lens, with its side facing the first lens being convex.

[0011] In one embodiment, the focusing lens group includes a fourth lens with positive optical power and a fifth lens with positive optical power arranged sequentially along the optical axis.

[0012] In one embodiment, the fourth lens is a biconvex lens;

[0013] The fifth lens is a concave-convex lens, and its side facing the fourth lens is concave.

[0014] In one embodiment, the output optical system of the fiber laser further includes a second plane mirror disposed between the fourth lens and the fifth lens. The second plane mirror is tilted relative to the optical axis to correct the aberrations caused by the first plane mirror.

[0015] In one embodiment, the first plane mirror, the second plane mirror, the collimating lens group, and the focusing lens group are all made of fused silica.

[0016] In one embodiment, the tilt angle A and the numerical aperture NA also satisfy NA≥sinA.

[0017] In one embodiment, the output optical system of the fiber laser further includes a photoelectric detection device, which has a filter hole for receiving a portion of the reflected light from the first plane mirror.

[0018] In one embodiment, the output optical system of the fiber laser further includes an electrically connected monitoring device and an alarm device. The monitoring device is electrically connected to the photoelectric detection device and is used to monitor the power of the reflected light. The alarm device is used to alarm for any abnormal conditions detected by the monitoring device.

[0019] An optical fiber, a first plane mirror, a collimating lens group, and a focusing lens group are arranged sequentially along the optical axis. The first plane mirror is tilted relative to the optical axis at an angle of A. The numerical aperture of the optical fiber's output port is NA, satisfying sinA ≥ 1 / 2NA.

[0020] The technical solution of this utility model, by setting the collimating lens group and the focusing lens group, enables the divergent laser in the optical fiber to be gradually collimated and focused to form an output beam that can converge to a point. Furthermore, by setting the tilted first plane mirror, the laser in the optical fiber, after being reflected by the first plane mirror, will not re-enter the output port of the optical fiber, thereby avoiding damage to the laser amplifier, resonant cavity and other optical devices caused by high-power backlight. In particular, by limiting the relationship between the tilt angle and the numerical aperture, the tilt angle is matched with the numerical aperture, so that the reflected light does not enter the optical fiber when facing output ports with different numerical apertures, thus improving the applicability of this system. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0022] Figure 1 A schematic diagram of an embodiment of the output optical system of the fiber laser provided by this utility model;

[0023] Figure 2 for Figure 1 Optical path diagram of the output optical system of a fiber laser;

[0024] Figure 3 for Figure 1 Workflow diagram of the photoelectric detection device.

[0025] Explanation of icon numbers:

[0026] 1000. Output optical system of fiber laser; 1. Fiber optic cable; 2. First plane mirror; 3. Collimating lens group; 31. First lens; 32. Second lens; 33. Third lens; 4. Focusing lens group; 41. Fourth lens; 42. Fifth lens; 5. Second plane mirror; 6. Photoelectric detection device; 61. Filter aperture; 7. Monitoring device; 8. Alarm device.

[0027] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0028] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present utility model.

[0029] It should be noted that if the embodiments of this utility model involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0030] Furthermore, if the embodiments of this utility model involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0031] One problem currently faced in fiber laser processing is that when processing highly reflective materials, such as gold, silver, and copper, the laser output from the fiber laser, after acting on the material surface, is reflected by the material and then enters the laser path again. When this reflected light reaches the laser oscillation end, it will be gradually amplified, eventually causing irreversible damage to the fiber laser optical system and burning out the optical components.

[0032] To address the aforementioned issues, the existing solution is to apply the laser output head to the material's working surface at a certain angle during processing. This way, most of the reflected laser light will travel along the angle and not enter the laser path. However, this method has two drawbacks: first, it reduces the power of the output laser acting on the processed material to some extent, resulting in a poorer processing effect; second, since laser transmission is reversible, some reflected light will still return to the laser's optical path, be amplified, and cause damage to the laser.

[0033] The main purpose of this invention is to propose an output optical system for fiber lasers, which aims to solve the problem of reflected light returning to the laser optical path and causing damage to the laser during current laser use.

[0034] To achieve the above objectives, please refer to Figure 1 and Figure 2 This utility model proposes an output optical system 1000 for a fiber laser, comprising an optical fiber 1, a first plane mirror 2, a collimating lens group 3, and a focusing lens group 4 arranged sequentially along the optical axis. The first plane mirror 2 is tilted relative to the optical axis at an angle of A. The numerical aperture of the output port of the optical fiber 1 is NA, satisfying sinA ≥ 1 / 2NA.

[0035] The technical solution of this utility model, by setting the collimating lens group 3 and the focusing lens group 4, enables the divergent laser light in the optical fiber 1 to be gradually collimated and focused to form an output beam that can converge to a point. Furthermore, by setting the tilted first plane mirror 2, the laser light in the optical fiber 1 will not re-enter the output port of the optical fiber 1 after being reflected by the first plane mirror 2, thereby avoiding damage to the laser amplifier, resonant cavity and other optical devices caused by high-power backlight. In particular, by limiting the relationship between the tilt angle and the numerical aperture, the tilt angle is matched with the numerical aperture, so that the reflected light does not enter the optical fiber 1 when facing output ports with different numerical apertures, thus improving the applicability of this system.

[0036] Furthermore, the tilt angle A and the numerical aperture NA also satisfy NA≥sinA. Considering the aberration introduced by the first plane mirror 2, a larger tilt results in a larger aberration, which affects the propagation of the beam and increases the complexity of subsequent correction of the tilted beam. By limiting the size of the tilt angle according to the numerical aperture, the aberration value is controlled within a reasonable range, ensuring the laser output quality of this optical system.

[0037] In a specific embodiment provided by this utility model, please refer to Figure 2The collimating lens group 3 includes a first lens 31 of positive optical power, a second lens 32 of negative optical power, and a third lens 33 of positive optical power, arranged sequentially along the optical axis. The first lens 31 is a biconvex lens, the second lens 32 is a concave-convex lens with a concave surface facing the first lens 31, and the third lens 33 is a concave-convex lens with a convex surface facing the first lens 31. The focusing lens group 4 includes a fourth lens 41 of positive optical power and a fifth lens 42 of positive optical power, arranged sequentially along the optical axis. The fourth lens 41 is a biconvex lens; the fifth lens 42 is a concave-convex lens with a concave surface facing the fourth lens 41. With this configuration, the system not only achieves collimation and focusing of the laser but also corrects aberrations in the optical system, improving the laser output quality of the device. It is worth mentioning that the exit angle of the light after being focused by the fourth lens 41 and the fifth lens 42 is opposite to the incident angle of the light at the light outlet of the optical fiber 1. The angles are similar in size and range within ±5°, which allows for better design of the convergence point based on the incident angle of the laser.

[0038] Furthermore, the output optical system 1000 of the fiber laser also includes a second plane mirror 5 disposed between the fourth lens 41 and the fifth lens 42. The second plane mirror 5 is tilted relative to the optical axis to correct the aberrations introduced by the first plane mirror 2. It should be noted that the tilt angle of the second plane mirror 5 is further optimized based on the coma introduced by the tilting of the front optical system, especially the first plane mirror 2.

[0039] It should be noted that the basic parameters of the output optical system 1000 of the fiber laser in one embodiment of this utility model are shown in Table 1, where the units of thickness and focal length are millimeters (mm).

[0040]

[0041] Please refer to Figure 1 and Figure 3 In one embodiment of this utility model, the output optical system 1000 of the fiber laser further includes a photoelectric detection device 6. The photoelectric detection device 6 is provided with a filter hole 61 for receiving a portion of the reflected light from the first plane mirror 2. With this configuration, the photoelectric detection device 6 can acquire the power of the reflected light in real time. By monitoring the reflected light, it can indirectly determine whether the light output from the fiber 1 is normal, and can also detect whether the tilt angle of the first plane mirror 2 is reasonable.

[0042] In one embodiment, the output optical system 1000 of the fiber laser further includes an electrically connected monitoring device 7 and an alarm device 8. The monitoring device 7 is electrically connected to the photoelectric detection device 6 and is used to monitor the power of the reflected light. The alarm device 8 is used to alarm for any abnormal conditions detected by the monitoring device 7. With this configuration, when the light output from the fiber 1 is abnormal, the alarm device 8 can issue an alarm in a timely manner, preventing prolonged malfunctions from damaging components and improving the safety of the system.

[0043] In this embodiment, the numerical aperture (NA) of the fiber 1 in the output optical system 1000 of the fiber laser is 0.2, the tilt angle (A) of the first plane mirror 2 is 10°, the diameter of the filter aperture 61 is 1 mm, the target surface of the photodetector 6 is 2.5 mm, the distance between the filter aperture 61 and the target surface is 5 mm, and the target surface is flush with the light outlet of the fiber 1. In the main optical path, the beam spot diameter is within the diffraction limit, the energy concentration is higher than 90%, and the wavefront phase difference (RMS) is < 1 / 10λ. Therefore, the deviation between the actual wavefront and the ideal wavefront is very small throughout the entire field of view of the optical system, indicating that the optical system in this embodiment has extremely high laser output quality.

[0044] Furthermore, the first plane mirror 2, the second plane mirror 5, the collimating lens group 3, and the focusing lens group 4 are all made of fused silica. It is worth noting that fused silica is an amorphous form of silicon dioxide, formed by rapidly cooling natural quartz after melting at high temperatures. It possesses excellent thermal shock resistance, remaining stable over a wide temperature range and is not easily broken by rapid temperature changes. Compared to other glass materials, fused silica has a lower coefficient of thermal expansion, meaning its dimensional changes are minimal during heating or cooling, significantly improving the power damage threshold of optical components.

[0045] The above description is merely an exemplary embodiment of the present utility model and does not limit the patent scope of the present utility model. Any equivalent structural transformations made based on the technical concept of the present utility model and the contents of the present utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present utility model.

Claims

1. An output optical system for a fiber laser, characterized in that, It includes an optical fiber, a first plane mirror, a collimating lens group, and a focusing lens group arranged sequentially along the optical axis. The first plane mirror is tilted relative to the optical axis at an angle of A. The numerical aperture of the optical fiber's output port is NA, satisfying sinA ≥ 1 / 2NA.

2. The output optical system of the fiber laser as described in claim 1, characterized in that, The collimating lens group includes a first lens with positive optical power, a second lens with negative optical power, and a third lens with positive optical power arranged sequentially along the optical axis.

3. The output optical system of the fiber laser as described in claim 2, characterized in that, The first lens is a biconvex lens; The second lens is a concave-convex lens, and its side facing the first lens is concave. The third lens is a concave-convex lens, with its side facing the first lens being convex.

4. The output optical system of the fiber laser as described in claim 2, characterized in that, The focusing lens group includes a fourth lens with positive optical power and a fifth lens with positive optical power arranged sequentially along the optical axis.

5. The output optical system of the fiber laser as described in claim 4, characterized in that, The fourth lens is a biconvex lens; The fifth lens is a concave-convex lens, and its side facing the fourth lens is concave.

6. The output optical system of the fiber laser as described in claim 4, characterized in that, The output optical system of the fiber laser also includes a second plane mirror disposed between the fourth lens and the fifth lens. The second plane mirror is tilted relative to the optical axis to correct the aberrations caused by the first plane mirror.

7. The output optical system of the fiber laser as described in claim 6, characterized in that, The materials of the first plane mirror, the second plane mirror, the collimating lens group, and the focusing lens group all include fused silica.

8. The output optical system of the fiber laser as described in claim 1, characterized in that, The tilt angle A and the numerical aperture NA also satisfy: NA≥sinA.

9. The output optical system of the fiber laser as described in claim 1, characterized in that, The output optical system of the fiber laser also includes a photoelectric detection device, which has a filter hole for receiving a portion of the reflected light emitted by the first plane mirror.

10. The output optical system of the fiber laser as described in claim 9, characterized in that, The output optical system of the fiber laser also includes an electrically connected monitoring device and an alarm device. The monitoring device is electrically connected to the photoelectric detection device and is used to monitor the power of the reflected light. The alarm device is used to alarm for any abnormal conditions detected by the monitoring device.

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