A spectrally continuously tunable narrow linewidth fiber-coupled semiconductor laser

Abstract

This invention relates to the field of semiconductor laser technology, specifically to a narrow-linewidth fiber-coupled semiconductor laser with continuously tunable spectrum. It includes at least one laser emitting unit, a fast-axis collimating lens, a slow-axis collimating lens, a beam conversion system, a Littrow grating, a beam processing device, and an fiber coupling device. The beam conversion system rotates the fast and slow axes of the collimated beam by 90 degrees, aligning the fast-axis direction (high beam quality, pure mode) with the beam selection direction of the Littrow grating for external cavity feedback and mode selection, thus obtaining a narrow-linewidth output. Continuous tuning of the output spectrum is achieved by rotating the angle of the Littrow grating. Multiple emitting units can be spatially spliced ​​and polarization-combined for power expansion, and coupled into the fiber via an equal optical path. This provides a high-brightness fiber-coupled laser with both narrow linewidth and continuous tuning capabilities, particularly suitable as a high-quality sub-beam for high-channel-number spectral synthesis.

Description

Technical Field

[0001] This invention relates to the field of semiconductor laser technology, and more specifically to a narrow-linewidth fiber-coupled semiconductor laser with continuously tunable spectrum. Background Technology

[0002] High-power, high-brightness direct semiconductor lasers have shown great application potential in materials processing, laser illumination, wireless power transmission, and as beacon light sources. However, semiconductor laser chips inherently possess a severe asymmetry in beam quality between the fast and slow axes. The fast axis has a large divergence angle but is a near-diffraction-limited single-mode, while the slow axis has a small divergence angle but is multimode, resulting in poor direct output beam quality (M² factor) and limited brightness. To improve brightness, spectral synthesis is an effective approach. By spatially combining multiple laser beams of different wavelengths into a single beam, the output power can be superimposed while maintaining a relatively constant beam quality. One of the core prerequisites for achieving high-performance spectral synthesis is that the laser units, acting as "sub-beams," must have narrow linewidths and controllable (tunable) center wavelengths. Narrow linewidths can compress the total bandwidth of the synthesis system, allowing more synthesis channels (i.e., more sub-beams of different wavelengths) to be accommodated within the limited bandwidth of the gain medium, thereby achieving a higher-power synthesized output. Spectral tunability facilitates system calibration, wavelength matching, and dynamic optimization.

[0003] Traditional techniques for spectral locking in semiconductor lasers primarily employ volume Bragg gratings (VBGs) or on-chip distributed Bragg mirrors (DBRs). However, these methods have certain limitations. In VBG-based external cavity feedback systems, the incident and feedback beams are typically located on opposite sides of the grating normal. This structure limits the flexibility of continuous, wide-range wavelength tuning, often resulting in discontinuous or limited tuning processes. While on-chip DBRs can provide narrow linewidths, their locked wavelength is fixed during manufacturing, preventing subsequent tuning, and their manufacturing process is complex and costly. More importantly, when using external cavities for mode selection, the slow axis of the semiconductor laser is multimode, leading to spatial mode impurities. This can introduce mode competition and crosstalk into the external cavity feedback, limiting the potential for further narrowing of the achievable spectral linewidth. Therefore, there is an urgent need in the field for a high-brightness fiber-coupled semiconductor laser solution capable of achieving narrower linewidths and continuously tunable spectra to meet the demands of high-end applications such as large-channel-number spectral synthesis.

[0004] Therefore, the existing technology still needs further development. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a narrow-linewidth fiber-coupled semiconductor laser with continuously tunable spectrum to solve the problems existing in the prior art.

[0006] To achieve the above-mentioned technical objectives, the present invention provides a narrow-linewidth fiber-coupled semiconductor laser with continuously tunable spectrum, comprising: At least one laser-emitting unit; A fast-axis collimating lens and a slow-axis collimating lens collimate the fast axis and slow axis of the laser emitted by the laser emitting unit, respectively. A beam conversion system that rotates the fast and slow axes of the collimated beam; and a Littrow grating installed after the beam conversion system to provide external cavity feedback and mode selection for the rotated fast-axis beam that is in the horizontal direction. A beam processing device disposed after the Littrow plane grating to redirect and / or combine the spectrally locked beam. And an optical fiber coupling device for coupling and outputting the combined beam.

[0007] Specifically, the laser emitting unit is a semiconductor laser single tube in COS, TO, C-mount, or CS package form.

[0008] Specifically, the optical path between the laser emitting unit and the output end of the optical fiber coupling device is of equal optical path, thereby improving the optical fiber coupling efficiency.

[0009] Specifically, the beam processing device includes a polarization combiner for polarization combining multiple beams.

[0010] Specifically, the beam processing device further includes a half-wave plate disposed in the incident optical path of the polarization beam combiner.

[0011] Specifically, the beam processing device includes a small mirror for deflecting the beam from the Littrow grating.

[0012] Specifically, multiple laser light-emitting units are stacked vertically, and the small reflector deflects the corresponding beam to achieve vertical beam splicing.

[0013] Specifically, the beam processing device also includes a large reflecting mirror for receiving and reflecting the beam deflected by the small reflecting mirror.

[0014] Specifically, the fiber optic coupling device includes a focusing lens for focusing the combined spatial beam.

[0015] Specifically, the fiber optic coupling device further includes an optical fiber for receiving the light emitted from the focusing lens.

[0016] Beneficial effects: The narrow-linewidth fiber-coupled semiconductor laser with continuously tunable spectrum provided by this invention has the following significant advantages compared to existing technologies: First, this invention creatively rotates the fast and slow axes of the laser beam by 90 degrees by introducing a beam conversion system. This rotates the fast axis direction, which originally had the best beam quality and the purest spatial mode (nearly single transverse mode), to a horizontal direction and aligns it with the diffraction feedback direction of the Littrow grating. This design is one of the core innovations of this invention. Because the fast axis direction is near single transverse mode with extremely pure spatial mode, when the beam in this direction is diffracted by the Littrow grating and fed back to the laser chip, the feedback efficiency is high, and it can effectively avoid mode competition and crosstalk problems caused by multiple transverse modes. The feedback mechanism mainly acts on longitudinal mode selection, thereby more efficiently suppressing side modes and obtaining a narrower spectral linewidth, providing a high-quality seed beam for subsequent high-channel-number spectral synthesis.

[0017] Secondly, this invention uses a Littrow-configured surface grating as the external cavity feedback element. The characteristic of a Littrow grating is that the incident light and the first-order diffracted light are on the same side of the grating normal, and when the incident angle equals the diffraction angle (i.e., the Littrow angle), the feedback light returns along the original path. By simply mechanically rotating the angle of this Littrow surface grating, its Littrow angle can be continuously changed, thereby achieving continuous and smooth tuning of the output laser wavelength. This tuning method overcomes the disadvantages of inconvenient and limited tuning range of traditional VBG gratings, and also avoids the limitation of the untunable wavelength of on-chip DBRs, making this laser highly flexible and adaptable in use, capable of quickly setting or scanning the output wavelength according to different application requirements.

[0018] Furthermore, the technical solution of this invention possesses excellent scalability and engineering practicality. By stacking multiple laser emission units vertically and using independent small reflectors for beam steering and spatial splicing, followed by brightness multiplication via a polarization combiner, the output power can be modularly increased while maintaining the independent narrow linewidth and tunable characteristics of each unit. The entire optical path employs an equal optical path design, ensuring perfect overlap of multiple beams at the fiber coupling end, greatly improving the efficiency and stability of coupling into a single fiber. Finally, a focusing lens couples the high-brightness combined beam into the fiber output, endowing the laser with the advantages of flexible transmission and symmetrical spot size, allowing it to be easily integrated into various application systems like a fiber laser. In summary, this invention successfully integrates the advantages of narrow linewidth, continuous spectral tuning, and high-brightness fiber output, providing a high-performance and highly practical semiconductor laser source solution. Attached Figure Description

[0019] Figure 1This is a schematic diagram of the composition of a narrow-linewidth fiber-coupled semiconductor laser with continuously tunable spectrum provided in a specific embodiment of the present invention; The above figures contain the following reference numerals: 1. Chip; 2. Fast-axis collimating lens; 3. Slow-axis collimating lens; 4. Beam conversion system; 5. Littrow plane grating; 6. Small mirror; 7. Large mirror; 8. Half-wave plate; 9. PBS polarization combiner; 10. Focusing lens; 11. Optical fiber. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Based on the embodiments in this application, other similar embodiments obtained by those skilled in the art without creative effort should all fall within the scope of protection of this application. Furthermore, directional terms mentioned in the following embodiments, such as "up," "down," "left," and "right," are only for reference to the directions in the accompanying drawings; therefore, the directional terms used are for illustrative purposes and not for limiting the invention.

[0021] The present invention will be further described below with reference to the accompanying drawings and preferred embodiments.

[0022] Please see Figure 1 This invention provides a narrow-linewidth fiber-coupled semiconductor laser with continuously tunable spectrum, comprising: At least one laser emitting unit 1; A fast-axis collimating lens 2 and a slow-axis collimating lens 3 collimate the fast axis and slow axis of the laser emitted from the laser emitting unit 1, respectively. A beam conversion system 4 that rotates the fast and slow axes of the collimated beam; A Littrow grating 5 is installed after the beam conversion system 4 to provide external cavity feedback and mode selection for the fast-axis beam that is rotated and is in the horizontal direction. A beam processing device disposed after the Littrow plane grating 5 to redirect and / or combine the spectrally locked beam. And an optical fiber coupling device for coupling and outputting the combined beam.

[0023] It should be further explained that the laser emitting unit 1 is the smallest light-emitting structure of the semiconductor laser. Its emitted original laser beam has different divergence angles on the fast axis (usually vertical) and slow axis (usually horizontal), with the fast axis divergence angle being much larger than the slow axis divergence angle. The fast-axis collimating lens 2 and the slow-axis collimating lens 3 are used to compress the divergence angles in these two directions to obtain a collimated or nearly collimated beam. The core function of the beam conversion system 4 is to interchange the fast and slow axis directions of the beam, i.e., to achieve a 90-degree rotation. After this rotation, the fast axis, originally in the vertical direction, becomes horizontal, and the slow axis, originally in the horizontal direction, becomes vertical. This rotation is for subsequent effective spectral selection and feedback in the horizontal direction (i.e., the rotated fast axis direction) using the Littrow grating 5.

[0024] Furthermore, the Littrow grating 5 is a reflective diffraction grating, and its working principle follows the grating equation. When the beam is incident at a specific angle (i.e., the Littrow angle), the diffracted light will return along its original path, forming optical feedback. Because the rotated fast-axis beam has good quality and a pure spatial mode (nearly single transverse mode), this feedback can efficiently select a specific wavelength and suppress other longitudinal modes, thereby achieving narrow linewidth output. By physically rotating the angle of the Littrow grating 5, the wavelength corresponding to its Littrow angle can be changed, thus achieving continuous tuning of the output spectrum. The spectrally locked beam then enters a beam processing device, which may include mirrors, polarization combiners, etc., for beam deflection, spatial combining, or polarization combining. Finally, the spatial light is efficiently coupled into the fiber optic cable 11 by an optical fiber coupling device, achieving flexible output. Figure 1 In the specific example shown, these components are connected in the optical path in the following order: chip 1, fast-axis collimator 2, slow-axis collimator 3, beam conversion system 4, Littrow plane grating 5, small mirror 6, large mirror 7, half-wave plate 8, PBS polarization combiner 9, focusing lens 10, and optical fiber 11.

[0025] For further information, please refer to [link / reference]. Figure 1 , Figure 1 A schematic diagram of an optical system for a specific embodiment of a narrow-linewidth fiber-coupled semiconductor laser with continuously tunable spectrum is shown, which fully reveals the end-to-end optical path design of the laser beam from generation, collimation, spectral processing, beam combining to fiber-coupled output. Figure 1The light-emitting unit on the left, i.e., chip 1, serves as the laser source. Its emitted beam is first collimated along the fast and slow axes by the fast-axis collimating lens 2 and slow-axis collimating lens 3, respectively. Then, the collimated beam enters the beam conversion system 4, which rotates the fast and slow axes of the beam by 90 degrees, making the fast axis horizontal. The rotated beam is then incident on the Littrow grating 5 located in the middle of the figure. This grating diffracts the horizontally oriented fast-axis beam, with the first-order diffracted light of a specific wavelength returning along its original path to form external cavity feedback, achieving narrow linewidth spectral locking and wavelength tuning. Another portion of the diffracted light continues to propagate as the output beam; this output beam is then deflected by a small mirror 6 and reflected by a large mirror 7; in part of the optical path, the beam passes through a half-wave plate 8 to adjust its polarization direction before entering the polarization combiner; then, the polarized beam is guided to the PBS polarization combiner 9, which combines multiple beams with perpendicular polarization in space; finally, the combined beam is focused by the focusing mirror 10 and efficiently coupled into the optical fiber 11 on the right, realizing a flexible laser output with high brightness, narrow linewidth and tunable wavelength. Figure 1 All optical components are accurately illustrated to show the main transmission path and feedback path of the laser, intuitively demonstrating the concept of equal optical path design and the integration process of spatial beamforming, polarization beam combining and fiber coupling.

[0026] Understandably, this scheme creatively combines beam rotation technology with a Littrow external cavity grating and is designed specifically to address the asymmetric beam quality of the fast and slow axes in semiconductor lasers. By rotating the beam grating (BTS), the fast axis direction, with the best beam quality and purest mode, is aligned with the diffraction feedback direction of the Littrow grating, significantly improving external cavity feedback efficiency and mode selectivity, thus achieving a narrower spectral linewidth. Simultaneously, the Littrow grating structure itself supports continuous wavelength tuning through rotation angles, overcoming the shortcomings of traditional volume Bragg gratings (VBGs) or distributed Bragg mirrors (DBRs) which have a wide locked spectral width and are inconvenient to tune. This laser integrates narrow linewidth and continuous tuning capability, making it an ideal sub-beam source for high-channel-number spectral synthesis to obtain high-brightness laser output.

[0027] Specifically, the laser light-emitting unit 1 is a semiconductor laser single tube in COS, TO, C-mount or CS package form.

[0028] It should be further explained that the laser emitting unit 1 is the foundation of the entire laser module. COS (Chipon Submount) packaging involves directly sintering the laser chip onto the heat sink, resulting in a compact structure and good heat dissipation. TO (Transistor Outline) packaging is a classic transistor-type package, with lower cost and wide application. C-mount packaging typically refers to a package form with a flange and standard threaded holes, facilitating mechanical installation and heat dissipation. CS (Channel Submount) packaging is commonly used in modules with multiple bar stacks. These packaging forms are all common semiconductor laser single-tube packages in this field. Their emitting units (i.e., chips) typically have multiple spatial modes (multimode) in the slow axis direction and a single mode or near-diffraction-limited single mode in the fast axis direction. The laser emitted by the chip is generally in a single polarization state (such as the TE mode), which lays the foundation for possible subsequent polarization beam combining. Using a single tube instead of bars as the basic unit is beneficial for obtaining better slow-axis beam quality from the source.

[0029] It is understandable that using these mature and diverse packaging forms as light-emitting units makes the technical solution of this invention highly flexible and widely applicable. Users can flexibly choose the most suitable single-tube type to construct laser modules according to specific requirements for output power, cost, heat dissipation, and packaging size, which is conducive to the rapid promotion and industrial application of the technology.

[0030] Specifically, the optical path between the laser emitting unit 1 and the output end of the optical fiber coupling device is an equal optical path, thereby improving the optical fiber coupling efficiency.

[0031] It should be further explained that equal optical path design means that the optical path length (optical path) from the center point of each parallel laser emitting unit 1 (in the scenario of multiple units being spatially combined) to the focal point finally coupled into the fiber 11 is equal or approximately equal. This requires careful design of the position of each optical element and the arrangement of mirrors during optical path layout to ensure that the beams from different optical path channels can achieve perfect spatial overlap and phase matching when finally focused. Figure 1 In the example shown, by properly setting the positions of the small reflector 6, the large reflector 7, and other steering elements, the optical path of each sub-beam can be adjusted to make them consistent.

[0032] Understandably, employing an equal optical path design is crucial for ensuring efficient and stable coupling of multiple beams into a single optical fiber 11. If the optical paths of the beams are inconsistent, they will not be able to converge simultaneously and accurately into the core of the optical fiber 11 at the focal plane of the focusing lens 10, resulting in a significant decrease in coupling efficiency and extreme sensitivity to mechanical vibration and thermal drift. The equal optical path design maximizes the effective collection and transmission of energy from all light-emitting units, improving the stability and output brightness of the entire system.

[0033] Specifically, the beam processing device includes a polarization combiner 9 for polarization combining multiple beams.

[0034] It should be further explained that the polarization beam combiner 9 is an optical element that utilizes the principle of polarization beam splitting. It is typically composed of a pair of right-angle prisms cemented together, with a polarization beam splitting film coated in between. This film highly reflects S-polarized light (polarization direction perpendicular to the incident plane) and highly transmits P-polarized light (polarization direction parallel to the incident plane). When two linearly polarized lights with mutually perpendicular polarization directions are incident at a specific angle, the P-light passes through the beam combiner, while the S-light is reflected. The two beams are spatially combined into a single beam output from the other end of the beam combiner, thus achieving a doubling of brightness (power is added while beam quality parameters remain essentially unchanged). Figure 1 In this example, polarization beam combiner 9 is used to combine two beams of light from the upper and lower optical paths.

[0035] Understandably, introducing polarization beam combining is an effective way to improve the output brightness of a laser module. Without significantly degrading beam quality, polarization beam combining allows the power of two laser beams to be directly added, effectively doubling the output power. This is crucial for direct semiconductor laser applications that demand high brightness output.

[0036] Specifically, the beam processing device further includes a half-wave plate 8 disposed in the incident light path of the polarization beam combiner 9.

[0037] It should be further explained that the half-wave plate 8 is a phase retardation plate. When its fast and slow axes form a specific angle with the polarization direction of the incident light, the polarization direction of the incident light can be rotated. The rotation angle is twice the azimuth angle of the wave plate. Figure 1 In the specific optical path shown, it is assumed that all light emitted from the laser emitting unit 1 has the same polarization direction (e.g., P-beam). One path of light passes through a half-wave plate 8 before reaching the polarization combiner 9. By precisely adjusting the rotation angle of the half-wave plate 8 (e.g., rotating it by 45 degrees), this P-beam can be converted into an S-beam. In this way, the two beams incident on the polarization combiner 9 have mutually perpendicular polarization states (one is P-beam, and the other is S-beam), thus satisfying the prerequisite for the efficient operation of the polarization combiner 9.

[0038] Understandably, using a half-wave plate 8 is a flexible and precise method for controlling the polarization state of the beam. It ensures that even if the output polarization states of all laser emitting units 1 are initially consistent, they can be adjusted to the perpendicular relationship required for polarization beam combining using simple optical elements, thus guaranteeing the working efficiency of the polarization beam combiner 9. It is an indispensable part of achieving efficient polarization beam combining.

[0039] Specifically, the beam processing device includes a small mirror 6 for deflecting the beam from the Littrow grating 5.

[0040] It should be further explained that the small reflector 6 is a small plane reflector whose main function is to change the direction of light propagation. Figure 1 In this example, the beam returning after diffraction and feedback by the Littrow grating 5 (its main beam is first-order diffracted light, with the portion returning along the original path used for feedback and the other portion as output light) needs its propagation direction adjusted for subsequent spatial stacking or guidance to the beam combining region. A small reflector 6 is positioned in the optical path after the Littrow grating 5 at a specific angle (e.g., 45 degrees) to deflect the horizontally propagating beam by 90 degrees, redirecting it to propagate vertically or in other desired directions. This design makes the optical path layout more compact and flexible.

[0041] Understandably, the placement of the small reflector 6 provides freedom for the compact design of the module and the spatial arrangement of multiple beams. It allows the spectrally processed beam to be guided from the horizontal plane to the vertical direction, creating conditions for subsequent stacking of multiple beams in the vertical direction (spatial beam combining), which is one of the key steps in realizing high-power modular design.

[0042] Specifically, multiple laser light-emitting units 1 are stacked vertically, and the small reflector 6 deflects the corresponding beam to achieve vertical beam splicing.

[0043] It should be further explained that, in order to obtain higher output power, the laser module of the present invention is typically composed of multiple laser emitting units 1 arranged in parallel. These laser emitting units 1 are not arranged on the same horizontal line during physical installation, but rather stacked vertically at certain intervals (step height). This step height needs to be designed, typically approximately equal to the spot size in the fast-axis direction after collimation by the fast-axis collimating mirror 2, to avoid beam occlusion. Each laser emitting unit 1 has its own independent collimation and spectral locking optical path (including the fast-axis collimating mirror 2, the slow-axis collimating mirror 3, the beam conversion system 4, and the Littrow grating 5). The beams output from each optical path are guided to approximately the same vertical direction after being deflected by their respective small reflectors 6. By precisely adjusting the angle and position of each small reflector 6, these beams from different heights can be arranged in parallel in space, achieving "stitching" in the vertical direction to form a composite beam with an elongated spot size on the slow axis (which has now been rotated to the vertical direction).

[0044] Understandably, vertical stacking and beam splicing via a small mirror (6) is an efficient spatial beam combining method. It allows multiple emitting units to share subsequent polarization combining and fiber-coupled optical paths, significantly improving system integration and power scaling capabilities. This design, while increasing total output power, ensures the spectral quality of each unit through independent spectral locking, allowing the synthesized beam to maintain narrow linewidth and tunable characteristics.

[0045] Specifically, the beam processing device also includes a large reflector 7 for receiving and reflecting the beam deflected by the small reflector 6.

[0046] It should be further explained that the large reflecting mirror 7 is a relatively large plane reflecting mirror, typically positioned at the far end of the optical path or serving as a common reflecting surface. Figure 1 In this example, the beams deflected from the individual small mirrors 6, although generally in the same direction, may still be spatially dispersed. The large mirror 7 acts as a common "collector" and "director," further reflecting all the beams from the different small mirrors 6 and guiding them to a common next optical element, such as the polarization combiner 9. By precisely designing the position and angle of the large mirror 7, better parallelism and spatial overlap of all sub-beams can be ensured when they reach the subsequent combiner element.

[0047] Understandably, the introduction of the large reflector 7 simplifies the merging optical path of multiple beams. It avoids setting up a complex subsequent steering system for each beam, making the optical path design simpler and more stable, and helping to reduce the overall size of the module. At the same time, the large reflector 7, as a common reference plane, helps to calibrate and adjust the entire multi-beam combining system.

[0048] Specifically, the fiber optic coupling device includes a focusing mirror 10 for focusing the combined spatial beam.

[0049] It should be further explained that the focusing lens 10 is typically a lens group consisting of one or more lenses, whose function is to converge the parallel or nearly parallel spatial beams, after spatial beam combining and / or polarization combining, to a very small focal point. The size and position of this focal point need to be precisely matched to the core size and end-face position of the fiber to be coupled 11. The numerical aperture (NA) of the focusing lens 10 should be greater than or equal to the numerical aperture of the fiber 11 to ensure that as much light energy as possible is captured. The choice of focal length requires a trade-off between the focused spot size and the system length. Figure 1In a specific application example, the focal length of the focusing lens 10 is preferably 9mm. The reason for choosing a focal length of 9mm is that, while ensuring sufficient working distance (facilitating installation and layout of other components), it provides suitable focusing capability, efficiently coupling the spot size that matches the fiber core diameter (e.g., 105μm) into the fiber. This is an optimal value that strikes a balance between compactness, assembly tolerance, and coupling efficiency.

[0050] Understandably, the focusing lens 10 is the core component for achieving efficient coupling of spatial light to the optical fiber 11. It concentrates laser energy distributed over a certain area into the micrometer-sized fiber core, a crucial step in ultimately achieving high-brightness fiber output. Optimizing the design and parameters of the focusing lens 10 is a direct means of improving the coupling efficiency of the entire system.

[0051] Specifically, the fiber optic coupling device further includes an optical fiber 11 for receiving the light emitted from the focusing lens 10.

[0052] It should be further explained that fiber 11 is the final output carrier of the laser, typically a large-core multimode fiber with a protective layer, such as fiber with a core diameter of 105 μm and a numerical aperture of 0.22. The end face of fiber 11 should be precisely fixed at the focal plane of focusing lens 10, and the center of the fiber core should be strictly aligned with the optical axis to receive the laser spot converged from focusing lens 10. The introduction of fiber 11 enables flexible transmission of laser output, allowing laser energy to be easily transmitted to a working position far from the laser body, greatly expanding application flexibility.

[0053] Understandably, using fiber optic cable 11 as the output end is one of the core advantages of this invention. It enables this narrow-linewidth, spectrally tunable, high-brightness semiconductor laser to be transmitted and delivered via lightweight and flexible optical fiber, just like traditional fiber lasers, paving the way for the direct application of semiconductor lasers in industrial processing, scientific research, and medical fields. The laser spot output from the fiber has good symmetry and high brightness, and can be directly used for subsequent spectral synthesis or as a high-quality light source.

[0054] The technical features described above can be combined arbitrarily. Although not all possible combinations of these technical features are described, any combination of these technical features should be considered to be covered by this specification, provided that such combination does not contain contradictions.

[0055] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A narrow-linewidth fiber-coupled semiconductor laser with continuously tunable spectrum, characterized in that, include: At least one laser light-emitting unit (1); A fast-axis collimating lens (2) and a slow-axis collimating lens (3) collimate the fast axis and slow axis of the laser emitted by the laser emission unit (1), respectively. A beam conversion system (4) that rotates the fast and slow axes of the collimated beam; and a Littrow grating (5) that is installed after the beam conversion system (4) to provide external cavity feedback and mode selection for the fast axis beam that is in the horizontal direction after rotation. A beam processing device disposed after the Littrow plane grating (5) for redirecting and / or combining spectrally locked beams; And an optical fiber coupling device for coupling and outputting the combined beam.

2. The spectrally continuously tunable narrow-linewidth fiber-coupled semiconductor laser according to claim 1, characterized in that, The laser light-emitting unit (1) is a semiconductor laser single tube in COS, TO, C-mount or CS package form.

3. The spectrally continuously tunable narrow-linewidth fiber-coupled semiconductor laser according to claim 1 or 2, characterized in that, The optical path between the laser light-emitting unit (1) and the output end of the optical fiber coupling device is an equal optical path.

4. The spectrally continuously tunable narrow-linewidth fiber-coupled semiconductor laser according to claim 1, characterized in that, The beam processing device includes a polarization combiner (9) for polarization combining multiple beams.

5. The spectrally continuously tunable narrow-linewidth fiber-coupled semiconductor laser according to claim 4, characterized in that, The beam processing device also includes a half-wave plate (8) disposed on the incident optical path of the polarization beam combiner (9).

6. The spectrally continuously tunable narrow-linewidth fiber-coupled semiconductor laser according to claim 1, characterized in that, The beam processing device includes a small mirror (6) for deflecting the beam from the Littrow grating (5).

7. The spectrally continuously tunable narrow-linewidth fiber-coupled semiconductor laser according to claim 6, characterized in that, Multiple laser light-emitting units (1) are stacked in the vertical direction, and the small reflector (6) deflects the corresponding beam to achieve beam splicing in the vertical direction.

8. The spectrally continuously tunable narrow-linewidth fiber-coupled semiconductor laser according to claim 6 or 7, characterized in that, The beam processing device also includes a large reflector (7) for receiving and reflecting the beam deflected by the small reflector (6).

9. The spectrally continuously tunable narrow-linewidth fiber-coupled semiconductor laser according to claim 1, characterized in that, The fiber optic coupling device includes a focusing lens (10) for focusing the combined spatial beam.

10. The spectrally continuously tunable narrow-linewidth fiber-coupled semiconductor laser according to claim 9, characterized in that, The fiber optic coupling device also includes an optical fiber (11) for receiving the light emitted from the focusing lens (10).

Images