Tandem edge sampling injection type line width compression module of blue-light semiconductor laser

Abstract

The invention discloses a blue-light semiconductor laser tandem edge sampling injection type line width compression module, and belongs to the technical field of blue-light semiconductor lasers. Comprising a collimation system, a reflection array and an external cavity feedback system, by means of a sampling feedback mode, single tubes in the module can be connected in series and influence each other so as to achieve the purposes of unifying wavelengths and further compressing the line width, and the influence of the difference of the wavelengths and the line width of the single tubes on line width compression is reduced. The mode that the edge low-brightness light spot serves as a sampling target is used, light beam splitting is avoided, the outer cavity part in the whole device is completely composed of plane reflection devices, the brightness of output light is kept unchanged, the brightness of the center light spot is reserved, and a combined light beam with higher brightness can be output while the debugging difficulty is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of blue semiconductor lasers, and more particularly relates to a blue semiconductor laser tandem edge sampling injection type linewidth compression module. BACKGROUND

[0002] High-power blue semiconductor lasers exhibit significant technical advantages and application potential in the fields of laser processing and laser medical treatment. In the field of laser processing, its short-wavelength (about 450 nm) characteristic significantly improves the light absorption rate of metal materials (such as copper, gold and other high-reflectivity materials), overcoming the energy loss problem caused by high reflectivity in traditional infrared laser processing, and is particularly suitable for precision manufacturing scenarios such as electronic packaging and new energy batteries. In the field of laser medical treatment, the blue light band can precisely act on target such as hemoglobin and melanin due to its specific biological tissue absorption characteristics, and has the advantages of high minimally invasive and fast postoperative recovery, providing an innovative tool for clinical diagnosis and treatment.

[0003] Due to the characteristics of GaN-based material system, the inherent linewidth of blue semiconductor lasers is generally wide (usually in the order of 1-10 MHz), which is much higher than that of near-infrared band lasers (up to kHz or even sub-kHz level), so linewidth compression means is needed to achieve narrow linewidth output. The current mainstream linewidth compression structures include Littrow structure and Littman structure, etc. Among them, the reflection part of the Littrow structure is completed by a blazed grating, the rotation is limited, the wavelength tuning range is narrow, and due to the application of diffraction splitting characteristics in most Littrow structures, different order diffraction beams are used for feedback and output, which reduces the output spot brightness; the plane mirror in the Littman structure rotates alone, obtains a larger wavelength tuning range, cooperates with a suitable grating, has a high diffraction efficiency, obtains strong feedback, and can obtain high-power, narrow-linewidth, wide-tuning-range laser output.

[0004] However, in the traditional Littman type linewidth compression device, the module linewidth is obtained by combining the wavelengths of each single tube, and since the linewidth locking paths of the single tubes in the module are independent, the differences in the wavelengths and linewidths of the single tubes will also cause the linewidth of the module to broaden, and the best linewidth compression effect cannot be obtained. In the adaptive condition linewidth compression device with external cavity feedback (CN116365351A), a blazed grating is used for linewidth compression by the single tube array, but the single tubes are relatively independent, the wavelength consistency is greatly affected by the assembly accuracy, and since the grating needs to feedback all the single tubes, the device is large in size. At the same time, since the feedback is mostly in the form of splitting into the external cavity, the light intensity of the output part is affected. In the common external cavity linewidth compression system (CN119297719A), in order to achieve linewidth compression, the beams of each single tube are split by a cubic beam splitter, so the final brightness is reduced. Summary of the Invention

[0005] In view of the above-mentioned defects or improvement needs of the existing technology, the purpose of this invention is to provide a blue semiconductor laser series edge sampling injection linewidth compression module, which aims to solve the problem of reduced output brightness after linewidth compression in traditional external cavity structures.

[0006] To achieve the above objectives, the present invention provides a blue semiconductor laser tandem edge-sampling injection linewidth compression module, comprising: a collimation system, a reflection array, and an external cavity feedback system; The collimation system includes a blue laser array and a fast and slow axis collimating lens group. The blue laser array is used to excite equally spaced and equally powerful blue laser beams. The fast and slow axis collimating lens group is used to collimate the blue laser beams and reduce the divergence angle of the blue laser beams. The reflection array includes a plane mirror array and a stepped mirror. The plane mirror array is used to spatially combine the blue laser beams output after passing through the fast and slow axis collimating mirror group. The combined blue laser beams are reflected by the stepped mirror and then connected in series. The outermost blue laser beam is reflected to the external cavity feedback system, and the other blue laser beams are combined and output. The external cavity feedback system includes a transmission grating and a reflector. The outermost blue laser beam passes through the diffraction grating, is reflected at the reflector, and then returns to the blue single-tube array, thus realizing the construction of a Littman-type external cavity. The transmission grating is used to compress the linewidth of the incident blue laser beam. By dispersing the wavelength, the reflector causes light of a specific wavelength to return to the blue single tube, resulting in linewidth compression.

[0007] Furthermore, the blue light single-tube array includes N parallel blue light single tubes, which are numbered from the first to the Nth blue light single tube. The fast and slow axis collimating lens group includes a fast axis collimating lens array and a slow axis collimating lens array. The fast axis collimating lens array includes N first cylindrical mirrors, and the slow axis collimating lens array includes N second cylindrical mirrors. The laser emitted by the N blue light single tubes passes through the N first cylindrical mirrors and the N second cylindrical mirrors in sequence to achieve fast axis and slow axis collimation.

[0008] Furthermore, the stepped reflector includes a first stepped reflector and a second stepped reflector, which are arranged in parallel. Each of the first and second stepped reflectors includes multiple reflective surfaces that are continuously arranged at 90° to each other. The first stepped reflector reflects the light emitted by the first blue laser tube back to the second blue laser tube, the light emitted by the third blue laser tube back to the fourth blue laser tube, the light emitted by the fifth blue laser tube back to the sixth blue laser tube, and so on, reflecting the light emitted by the (N-1)th blue laser tube back to the Nth blue laser tube. The second stepped reflector reflects the light emitted by the second blue laser tube back to the third blue laser tube, the light emitted by the fourth blue laser tube back to the fifth blue laser tube, and so on, reflecting the light emitted by the Nth blue laser tube. After reflection by the plane mirror, the light returns along the original path. Since the optical path is reversible, the N blue laser beams ultimately form feedback and are connected in series.

[0009] Furthermore, the transmission grating has a +1 order diffraction efficiency of 94% for S-polarized light at 444 nm.

[0010] Furthermore, the front end transmittance of each blue light tube is 95%.

[0011] Furthermore, the central axis of each optical lens in the narrow linewidth compression device coincides with the central axis of the beam, and each lens is coated with a blue light anti-reflection film.

[0012] Furthermore, the narrow linewidth compression device also includes a water cooling system; the water cooling system includes chilled water pipes and a water chiller; The water chiller is connected to the blue light single-tube array via the cold water pipe, and the water chiller is used to dissipate heat from the blue light single-tube array.

[0013] Compared with existing technologies, the technical solutions conceived in this invention propose a sampling feedback method that allows individual tubes in the module to be connected in series and influence each other to achieve wavelength uniformity and further compress linewidth, reducing the impact of differences in single-tube wavelength and linewidth on linewidth compression. Since the grating in the device only needs to provide feedback on the beam emitted by one single tube, it helps reduce the required grating area, facilitating miniaturization and cost reduction. Furthermore, the innovative use of low-brightness edge spots as sampling targets avoids beam splitting, ensuring that the entire external cavity of the device is composed of planar reflective devices, maintaining constant output brightness while preserving the brightness of the central spot. This reduces debugging difficulty while enabling the output of a higher-brightness combined beam. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the linewidth compression module in a specific embodiment of the present invention.

[0015] Figure 2 This is a structural diagram of the collimation system according to a specific embodiment of the present invention.

[0016] Figure 3 This is a structural diagram of a spatial bundle combining device according to a specific embodiment of the present invention.

[0017] Figure 4 This is a schematic diagram of a stepped reflector series system according to a specific embodiment of the present invention.

[0018] Figure 5 This is a schematic diagram of the output end beam splitting in a specific embodiment of the present invention.

[0019] Figure 6 This is a structural diagram of the external cavity of the transmission grating according to a specific embodiment of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0021] This invention provides a blue semiconductor laser cascaded edge-sampling injection linewidth compression module, comprising a blue single tube 1-6, a fast-axis collimating mirror array 7, a slow-axis collimating mirror array 8, a plane mirror 9-14, a stepped reflector 15-16, a reflector 17, a reflector 18, a transmission grating 19, and an external cavity reflector 20.

[0022] Specifically, the following detailed description is provided in conjunction with optional embodiments: In this example, as Figure 1The diagram shows the principle of the linewidth compression module. The laser emitted by the blue light array composed of blue single tubes 1-6 is collimated by a fast-axis collimating mirror array composed of cylindrical mirrors 7 and a slow-axis collimating mirror array composed of cylindrical mirrors 8. After the direction is adjusted by a reflecting mirror array composed of plane mirrors 9-14, spatial beam combining is achieved. Specifically, the laser emitted by blue single tube 1 is reflected by reflecting mirror 17 and then subjected to wavelength tuning and linewidth compression in the Littman external cavity composed of transmission grating 19 and reflecting mirror 20, resulting in blue single tube 1 outputting a specific wavelength laser with a narrow linewidth. Note that after the laser emitted by blue single tube 1 passes through the stepped reflector 15, the edge of the light spot is truncated for sampling feedback. Stepped reflector 15 connects the beams of blue single tubes 1 and 2, 3 and 4, and 5 and 6 in series, while stepped reflector 16 connects the beams of blue single tubes 2 and 3, and 4 and 5 in series. A beam overflowing from blue single tube 6 is reflected by reflecting mirror 18 and used to enhance feedback. Thus, the six blue light tubes are connected in series and influence each other. The light from the blue light tube 1, after linewidth compression and wavelength selection, is injected into other cavities. Finally, the entire module outputs a high-power laser beam with good coherence, narrow linewidth and uniform wavelength.

[0023] In this example, as Figure 2 The diagram shows the collimation system structure. The uncollimated laser beam emitted by the blue single tube 1 is collimated on the fast axis after passing through the cylindrical mirror 7, and then on the slow axis after passing through the cylindrical mirror 8, finally outputting a high-quality laser beam with a small divergence angle.

[0024] In this example, as Figure 3 The diagram shows the structure of a spatial beam combiner. A blue laser array composed of single blue light tubes 1 passes through a fast-axis collimating mirror array composed of cylindrical mirrors 7 and a slow-axis collimating mirror array composed of cylindrical mirrors 8, outputting six beams with extremely small divergence angles. A reflector array composed of plane mirrors 9-14 is angled at 45° to the laser beam direction, causing the laser beams to rotate 90° after passing through the array and to be closely arranged along the fast axis with very small gaps in space, thereby increasing power density.

[0025] In this example, as Figure 4 The diagram shows a stepped-mirror series system. Stepped-mirror 15 reflects light emitted from blue single-tube 1 back to blue single-tube 2, light emitted from blue single-tube 3 back to blue single-tube 4, and light emitted from blue single-tube 5 back to blue single-tube 6. Stepped-mirror 16 reflects light emitted from blue single-tube 2 back to blue single-tube 3, light emitted from blue single-tube 4 back to blue single-tube 5, and light emitted from blue single-tube 6, after being reflected by plane mirror 18, returns along the same path. Note that due to the reversibility of the optical path, there are also beams propagating in the opposite direction in the above optical path. Thus, the six laser beams form feedback and are connected in series into a whole. Through the stepped-mirror series system, the six laser beams have strong coherence.

[0026] In this example, as Figure 5 The diagram shows the beam splitting at the output end. After the output beam from the six lasers is combined, it is truncated at the edges by stepper mirrors 15 and 16, while the central high-brightness portion remains unaffected. The first beam, after being split by mirror 17, enters the external cavity as feedback light. It then passes through the Littman external cavity formed by the transmission grating 19 and mirror 20 before returning to the lasers along the same path, providing feedback and ensuring good beam coherence. Furthermore, because stepper mirrors 15 and 16 connect the lasers in series, all lasers influence each other, resulting in a combined beam with advantages such as narrow linewidth, high brightness, consistent wavelength, and high coherence. The final output is a combined beam from five lasers. Since only planar reflective optics are used in the optical path, the beam quality is maintained from laser collimation to the output end, and the brightness remains unaffected.

[0027] In this example, as Figure 6 The diagram shows the external cavity structure of the transmission grating. The laser beam emitted by the blue laser tube 1 is collimated by cylindrical mirrors 7 and 8, then rotates 90° after passing through a plane mirror 9 placed at a 45° angle. After edge sampling and feedback by the stepped reflector 15, the central portion of the beam rotates 90° after passing through a reflector 17 placed at a 45° angle, separating from the output beam path. After passing through the transmission grating 19, it is reflected at the reflector 20 and returns to the blue laser tube 1 along the same path, thus realizing the construction of a Littman-type external cavity. Continuous wavelength tuning can be achieved by rotating the angle of the reflector 20.

[0028] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A blue semiconductor laser cascaded edge-sampling injection linewidth compression module, characterized in that, include: Collimation system, reflective array, external cavity feedback system; The collimation system includes a blue laser array and a fast and slow axis collimating lens group. The blue laser array is used to excite equally spaced and equally powerful blue laser beams. The fast and slow axis collimating lens group is used to collimate the blue laser beams and reduce the divergence angle of the blue laser beams. The reflection array includes a plane mirror array and a stepped mirror. The plane mirror array is used to spatially combine the blue laser beams output after passing through the fast and slow axis collimating mirror group. The combined blue laser beams are reflected by the stepped mirror and then connected in series. The outermost blue laser beam is reflected to the external cavity feedback system, and the other blue laser beams are combined and output. The external cavity feedback system includes a transmission grating and a reflector. The outermost blue laser beam passes through the diffraction grating, is reflected at the reflector, and then returns to the blue single-tube array, thus realizing the construction of a Littman-type external cavity. The transmission grating is used to compress the linewidth of the incident blue laser beam.

2. The linewidth compression module according to claim 1, characterized in that, The blue light single-tube array includes N parallel blue light single tubes, numbered from the first to the Nth. The fast and slow axis collimating lens group includes a fast axis collimating lens array and a slow axis collimating lens array. The fast axis collimating lens array includes N first cylindrical mirrors, and the slow axis collimating lens array includes N second cylindrical mirrors. The laser emitted by the N blue light single tubes passes through the N first cylindrical mirrors and the N second cylindrical mirrors in sequence to achieve fast and slow axis collimation.

3. The linewidth compression module according to claim 1, characterized in that, The stepped reflector includes a first stepped reflector and a second stepped reflector, which are arranged in parallel. Each of the two reflectors includes multiple reflective surfaces that are continuously arranged at 90° to each other. The first stepped reflector reflects the light emitted by the first blue laser tube back to the second blue laser tube, the light emitted by the third blue laser tube back to the fourth blue laser tube, the light emitted by the fifth blue laser tube back to the sixth blue laser tube, and so on, and the light emitted by the (N-1)th blue laser tube back to the Nth blue laser tube. The second stepped reflector reflects the light emitted by the second blue laser tube back to the third blue laser tube, the light emitted by the fourth blue laser tube back to the fifth blue laser tube, and so on, and the light emitted by the Nth blue laser tube is reflected by a plane mirror and then returns along the original path. Since the optical path is reversible, the N blue laser beams eventually form feedback and are connected in series.

4. The linewidth compression module according to claim 1, characterized in that, The transmission grating has a +1 order diffraction efficiency of 94% for S-polarized light at 444 nm.

5. The linewidth compression module according to claim 1, characterized in that, The front surface transmittance of each blue light tube is 95%.

6. The linewidth compression module according to claim 2, characterized in that, The central axis of each optical lens in the narrow linewidth compression device coincides with the central axis of the beam, and each lens is coated with a blue light anti-reflection film.

7. The linewidth compression module according to claim 1, characterized in that, The narrow linewidth compression device also includes a water cooling system; the water cooling system includes chilled water pipes and a water chiller. The water chiller is connected to the blue light single-tube array via the cold water pipe, and the water chiller is used to dissipate heat from the blue light single-tube array.

Images