Pump cavity structure of multi-pump source disk laser

Abstract

The present invention discloses a multi-pump source disk laser pump cavity structure, comprising a proximal end and a distal end. The structure is characterized by comprising: N pump laser beams, N beam collimators, N parabolic reflector groups, a laser gain medium, and N deflection optical prism groups, wherein N is greater than or equal to 2; the wavelengths of the pump laser beams are all within the absorption spectrum of the laser gain medium; the laser gain medium includes a dielectric reflective surface; the parabolic reflector group is provided with a plurality of reflective curved surfaces, each of which is a parabola; the pump laser beams are incident after passing through one of the beam collimators, and after multiple reflections, are absorbed by the laser gain medium to form a pump spot. The present invention has the beneficial effect of effectively solving the problem of asymmetric intensity distribution of large-diameter pump spots, resulting in a high-power pump spot with a flat-top light effect.

Description

Technical Field

[0001] The invention belongs to the field of lasers, and in particular relates to a multi-pump source disk laser pump cavity structure. Background Art

[0002] Since the invention of the disk laser in 1993, the laser gain medium used in the disk laser has a thickness of only 100 to 300 microns. Combined with back jet cooling technology, it can achieve excellent heat dissipation of the laser gain medium, thereby achieving extremely high laser output power, laser pulse energy, and excellent beam quality. However, due to the small thickness of the laser gain medium, a special pump optical path design is required to allow the pump laser to pass through the laser gain medium multiple times to obtain a sufficiently high absorption rate. In order to ensure that the pump light is uniformly absorbed by the laser gain medium, the designed pump optical path needs to be able to make the spot formed by the pump light superimposed on the laser gain medium have the effect of a flat-top spot.

[0003] Patent EP0 632 551B1 discloses a method that utilizes multiple pump light reflectors and auxiliary reflectors, along with a spherical mirror to deflect the pump light. This method reflects the pump light reflected from a laser gain medium multiple times back onto the laser gain medium, ultimately superimposing it to form a flat-top pump spot. Ideally, the better the collimation of the pump light beam, the closer the resulting pump light spot is to the ideal flat-top spot. However, in actual use, after multiple reflections, the pump light's transmission distance increases, causing the pump light beam to continue to diverge, preventing the final pump light spot from forming a flat-top spot. Furthermore, the laser gain medium undergoes certain thermal deformation upon heating, acting as a lens with a focal length of f, exacerbating the divergence of the pump light beam. Furthermore, assuming the absorption coefficient of the laser gain medium remains unchanged, the power of the pump light initially incident on the laser gain medium is partially absorbed, which is greater than the power of the pump light absorbed by the pump light that is deflected and reflected and then re-enters the laser gain medium. Repeated deflection, reflection, and absorption typically result in a pump spot with a non-ideal flat-top intensity distribution. Instead, the intensity distribution of the pump spot near the first incident spot is higher than that near the last incident spot. This phenomenon becomes more pronounced as the pump spot diameter increases. For example, when the spot diameter is greater than 10 mm, the intensity distribution of the pump spot is likely to be significantly higher on one side than on the other. This non-flat-top pump spot reduces the matching between the pump spot and the laser mode in the laser, thereby reducing parameters such as the output laser beam quality and output power.

[0004] Although several patents and academic articles, such as patent EP1 252 687B1, patent CN 103688426 B, doctoral thesis "Pumping optical system and resonator for disk lasers" ISBN 3-8316-0173-9, and doctoral thesis "Disk laser with kilowatt constant wave power" ISBN 3-89675-763, have designed a variety of improved pump optical design structures, such as using parabolic reflectors to compensate for the divergence angle of the pump beam, using a telephoto imaging system to compensate for the equivalent focal length caused by thermal deformation of the laser gain medium, or using an asymmetric double prism to improve the imaging effect of the telephoto imaging system, none of them have effectively solved the aforementioned problem of non-flat top intensity distribution of large-diameter pump spot. Summary of the Invention

[0005] The object of the present invention is to provide a multi-pump source disk laser pump cavity structure that can solve or partially solve the above problems.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A multi-pump source disk laser pump cavity structure, comprising a proximal end and a distal end, characterized in that it comprises: two groups of pump laser beams, two groups of beam collimators, two groups of parabolic reflector groups, one laser gain medium, and two groups of deflection optical prism groups, wherein the wavelengths of the pump laser beams are all within the absorption spectrum of the laser gain medium;

[0008] The laser gain medium includes a medium reflection surface, and the parabolic reflector group is provided with a plurality of reflection curved surfaces, and the reflection curved surfaces are all parabolic;

[0009] The pump laser beams at the proximal end are respectively passed through a beam collimator and then incident on the parabolic reflector group at the distal end, so as to undergo multiple reflections between a deflection optical prism group, a reflective curved surface, and a medium reflective surface, and pass through the laser gain medium multiple times to be absorbed by the laser gain medium and form a pump light spot;

[0010] The deflection optical prism groups are all coaxial annular structures composed of multiple prism pairs, each of which includes two prisms, and both prisms have reflection planes that form a 90° angle with each other; the reflection planes of all prism pairs are evenly distributed in an annular shape toward the distal end;

[0011] The two groups of pump laser beams include a first pump laser beam and a second pump laser beam, the two groups of parabolic reflector groups include a first parabolic reflector group and a second parabolic reflector group; the two groups of deflection optical prism groups include a first deflection optical prism group and a second deflection optical prism group;

[0012] The first pump laser beam and the second pump laser beam have the same optical power, and the spot diameters formed by them on the laser gain medium are the same, and they overlap on the laser gain medium;

[0013] The first pump laser beam, the first deflection optical prism group, and the first parabolic reflector are located in the outer ring of the pump cavity structure, and the second pump laser beam, the second deflection optical prism group, and the second parabolic reflector are located in the inner ring of the pump cavity structure;

[0014] The input position of the second pump laser beam is in the inner ring, and the input position of the first pump laser beam is in the outer ring; the incident angle of the second pump laser beam on the laser gain medium is smaller than the incident angle on the laser gain medium, and the beam collimator corresponding to the second pump laser beam has a larger magnification.

[0015] Preferably, the laser gain medium and the medium reflection surface are both circular; the parabolic reflector group is a ring structure, on which a plurality of the reflection curved surfaces are arranged at equal intervals around its circumference; the medium reflection surface and the parabolic reflector group are coaxial, and the focal points of all the reflection curved surfaces on the parabolic reflector group are located on the medium reflection surface; the laser gain medium is located between the medium reflection surface and the parabolic reflector group.

[0016] Preferably, the reflective curved surfaces all have the same equivalent focal length.

[0017] Preferably, the deflection optical prism assembly includes a plane reflector or a corner cone reflector, which is used to return the incident pump laser beam along its original path.

[0018] Preferably, both the reflective curved surface and the reflective flat surface are coated with a first dielectric film having a high reflectivity for the pump laser beam.

[0019] Preferably, the thickness of the laser gain medium is 0.15 to 0.35 mm, and it includes a front surface facing the parabolic reflector group and a rear surface facing away from the parabolic reflector group; the front surface is coated with a second dielectric film that increases the transmittance of the pump laser beam; and the rear surface is coated with a third dielectric film that has a high reflectivity for the pump laser beam to form the dielectric reflection surface.

[0020] Preferably, the laser gain medium is fixed to the heat sink by welding, gluing or bonding, and the other side of the heat sink is in contact with a jet coolant to cool the laser gain medium. The heat sink is made of tungsten copper, diamond, sapphire, silicon carbide or aluminum nitride ceramic.

[0021] Preferably, the pump laser beam has 12, 16 or 24 reflection areas on the parabolic reflector assembly, and the light spots of the pump laser beam on the reflection areas do not overlap.

[0022] The beneficial effects of the present invention are: effectively solving the problem of asymmetric intensity distribution of large-diameter pump light spots, so that the high-power pump light spots finally obtained have a flat-top light effect distribution, which can further improve the mode matching effect between the pump laser and the laser mode in the resonator, and improve the conversion efficiency of the laser and the beam quality of the output laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A multi-pump source disk laser pump cavity structure according to the first embodiment of the present invention;

[0024] Figure 2 A multi-pump source disk laser pump cavity structure of the second embodiment;

[0025] Figure 3 It is a front view structural diagram of the first embodiment;

[0026] Figure 4 Schematic diagram of the distribution of the reflection area of ​​the pump laser beam on the hollow parabolic reflector of the third embodiment;

[0027] Figure 5 Schematic diagram of the distribution of the reflection area of ​​the pump laser beam on the hollow parabolic reflector of the fourth embodiment;

[0028] Figure 6 Schematic diagram of the structure of the optical deflection prism group corresponding to the outer ring pump laser beam of the first embodiment;

[0029] Figure 7 Schematic diagram of the structure of the optical deflection prism group corresponding to the inner ring pump laser beam of the first embodiment;

[0030] Figure 8 A simulation diagram of the intensity distribution of the pump spot formed by the disk laser pump cavity in the prior art;

[0031] Figure 9 A two-dimensional light intensity map in the horizontal direction of a simulation diagram of the pump spot intensity distribution formed by a single pump source;

[0032] Figure 10 This is a simulation diagram of the intensity distribution of the pump spot formed by the disk laser pump cavity using dual pump sources;

[0033] Figure 11 This is a two-dimensional light intensity map in the horizontal direction of a simulation diagram of the pump spot intensity distribution formed by using dual pump sources. DETAILED DESCRIPTION

[0034] The technical solution of this patent is further described in detail below in conjunction with specific implementation methods.

[0035] In the description of the present invention, it should be noted that the terms "far", "near", "inside", "outside", "upper", "lower", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the present invention.

[0036] like Figures 1 to 11 As shown, the present invention discloses a multi-pump source disk laser pump cavity structure.

[0037] See also Figure 1 、 Figure 2 、 Figure 6 and Figure 7 , which shows a specific embodiment of the present invention, a dual-pump source disk laser pump cavity structure. It includes: two groups of pump laser beams, namely a first pump laser beam 8 and a second pump laser beam 9; two groups of beam collimators, namely a first beam collimator 6 and a second beam collimator 7; two groups of annular and coaxial parabolic reflectors, namely a first parabolic reflector group 1 and a second parabolic reflector group 2; a disk-shaped laser gain medium 3; and two groups of deflection optical prisms, namely a first deflection optical prism group 4 and a second deflection optical prism group 5.

[0038] The wavelengths of both pump laser beams fall within the absorption spectrum of the laser gain medium 3. The first parabolic reflector assembly 1 and the second parabolic reflector assembly 2 are equipped with several parabolic reflective surfaces (not labeled). The deflection optical prism assemblies are coaxial ring structures composed of multiple prism pairs. Each prism pair includes two prisms, each with reflective planes (not labeled) at 90° angles to each other. The reflective planes of all prism pairs are evenly distributed in a circular pattern toward the distal end.

[0039] The reflection curved surface and the reflection flat surface are both coated with a first dielectric film with high reflectivity in the wavelength band of the pump laser beam.

[0040] After being collimated by the first beam collimator 6, the first pump laser beam 8 is incident on point A1 on the second parabolic reflector 2, and then reflected and focused on the laser gain medium 3; after part of the laser energy is absorbed, the remaining first pump laser beam 8 is reflected to point A2 of the second parabolic reflector 2, and then reflected again to the first deflection optical prism group 4; the first deflection optical prism group 4 is located in the outer ring of the pump cavity structure and is composed of multiple prism pairs, each prism pair consisting of two prisms P1 and P2 at a 90° angle to each other. After the first deflection optical prism group 4 deflects the transmission direction of the first pump laser beam 8 by 180°, it is incident on A3 via the second parabolic reflector 2; similarly, under the action of the first deflection optical prism group 4 and the second parabolic reflector 2 in the outer ring, the first pump laser beam 8 is incident on the laser gain medium 3 multiple times, reaches the plane reflector 10, is then reflected by it, returns along the original optical path, and is incident on the laser gain medium 3 multiple times again; finally, the first pump laser beam 8 is absorbed by the laser gain medium 3.

[0041] After being collimated by the second beam collimator 7, the second pump laser beam 9 is incident on the A1 of the first parabolic reflector 1, and then is reflected and focused on the laser gain medium 3; the remaining second pump laser beam 9 after absorbing part of the laser energy is reflected to the B2 of the first parabolic reflector 1, and then is reflected again to the second deflection optical prism group 5; the second deflection optical prism group 5 is located in the inner ring of the pump cavity structure, and is composed of two prism pairs, each prism consisting of two prisms P3 and P4 or prisms P5 and P6 that are at an angle of 90 degrees to each other; the second After the second deflection optical prism group 5 deflects the transmission direction of the second pump laser beam 9 by 180°, it is incident on point B3 via the first parabolic reflector 1; similarly, under the action of the first deflection optical prism group 4 and the first parabolic reflector 1 in the inner ring, the second pump laser beam 9 is incident on the laser gain medium 3 multiple times, and then is incident on the corner reflector composed of prism P3 and prism P6. The transmission direction of the beam is deflected by 180°, returns along the original optical path, and is incident on the laser gain medium 3 multiple times again; finally, the second pump laser beam 9 is absorbed by the laser gain medium.

[0042] The first deflection optical prism group 4 in the outer ring is composed of a plurality of 3 or more prism pairs, each prism pair consisting of two prisms P1 and P2 at an angle of 90° to each other; thereby, the optical path of the first pump laser beam 8 is symmetrically distributed in a petal-like manner, and the deflected beam is only reflected once between every two prisms at an angle of 90° to each other; this structure can prevent the first pump laser beam 8 from crossing over the laser gain medium and being blocked by the second deflection optical prism group 5 in the inner ring.

[0043] The second deflection optical prism group 5 in the inner ring is composed of two prism pairs, each prism is composed of two prisms P3, P4 or P5, P6 with a 90° angle between each other; the optical path distribution is asymmetrical, and the deflected light beam will be reflected multiple times 2 or 3 times between different positions of each two prisms with a 90° angle between each other.

[0044] The first parabolic reflector 1 and the second parabolic reflector 2 are coaxial, and their equivalent focal lengths may be the same or different, as long as their equivalent focal planes are both located on the plane of the laser gain medium 3 .

[0045] The wavelengths of the first pump laser beam 8 and the second pump laser beam 9 emitted by the two pump light sources can be the same or different. When using pump sources with different wavelengths, the wavelengths of the first pump laser beam 8 and the second pump laser beam 9 must be within the absorption spectrum of the laser gain medium. The first pump laser beam 8 and the second pump laser beam 9 have the same optical power, and the spots formed on the laser gain medium 3 have the same diameter. They are symmetrically distributed about a common center line and overlap on the laser gain medium 3.

[0046] The first beam collimator 6 and the second beam collimator 7 are not the same; and further, since the incident angle of the second pump laser beam 9 input at the inner ring on the laser gain medium 3 is smaller than the incident angle of the first pump laser beam 8 input at the outer ring on the laser gain medium 3, the second beam collimator 7 should have a slightly larger magnification to ensure that the spot diameter of the second pump laser beam 9 on the laser gain medium 3 is the same as the spot diameter of the first pump laser beam 8 on the laser gain medium 3.

[0047] The thickness of the laser gain medium 3 is 0.15 to 0.35 mm. The surface facing the parabolic reflector 2 is the front surface, and the opposite surface is the rear surface. The front surface is coated with a second dielectric film that increases the transmittance of the first pump laser beam 8, the second pump laser beam 9, and the seed light (not shown). The rear surface is coated with a third dielectric film that has a high reflectivity for the first pump laser beam 8, the second pump laser beam 9, and the seed light.

[0048] The laser gain medium 3 is fixed to a heat sink (not shown) by welding, gluing, or chemical bonding. The other side of the heat sink is in contact with a jet of coolant to cool the laser gain medium 3. The heat sink can be made of a material with high thermal conductivity, such as tungsten copper (CuW), diamond, sapphire, silicon carbide (SiC), or aluminum nitride (AlN).

[0049] Figure 8A simulated diagram of the intensity distribution of the pump spot formed by a disk laser pump cavity using a single pump source shows that the intensity distribution is symmetrical vertically but not horizontally. "incoherent irradiance" represents incoherent irradiance; "X coordinate value" represents the X-axis coordinate, and "Y coordinate value" represents the Y-axis coordinate.

[0050] Figure 9 This is a two-dimensional intensity diagram in the horizontal direction of a simulated diagram of the pump spot intensity distribution formed by a single pump source. As can be seen from the figure, in the horizontal direction, the intensity on the right side of the pump spot is higher than that on the left side;

[0051] Figure 10 This is a simulation diagram of the intensity distribution of the pump spot formed by the disk laser pump cavity using dual pump sources. As can be seen from the figure, the light intensity distribution is centrally symmetrical and has a good flat-top effect.

[0052] Figure 11 This is a two-dimensional light intensity diagram in the horizontal direction of a simulation diagram of the pump spot intensity distribution formed by dual pump sources. It can be seen from the figure that the intensity on the right side of the pump spot is at the same level as the intensity on the left side, and the flat-top effect is good.

[0053] Thus, the present invention cleverly uses dual pump sources and two sets of deflection optical prisms to generate two pump light spots, whose intensity distributions are symmetrical and superimposed, effectively solving the problem of asymmetric intensity distribution of large-diameter pump light spots. The resulting high-power pump light spot has a flat-top light effect distribution, which can further improve the mode matching effect between the pump laser and the laser mode in the resonator, thereby improving the conversion efficiency of the laser and the beam quality of the output laser.

[0054] Figure 2 Specific embodiment 2 is shown, which is a dual-pump source disk laser pump cavity structure with only one parabolic reflector, and its equivalent focal plane is located on the plane of the laser gain medium 3.

[0055] Figure 4 Specific embodiment 3 is shown, in which the first pump laser beam 8 located in the outer ring has 12 reflection areas on the parabolic reflector, which are respectively recorded as A1, A2, ..., A12; the second pump laser beam 9 located in the inner ring has 16 reflection areas on the parabolic reflector, which are respectively recorded as B1, B2, ..., B16.

[0056] Figure 5 Specific embodiment 4 is shown, in which the first pump laser beam 8 located in the outer ring has 24 reflection areas on the parabolic reflector, which are respectively recorded as A1, A2, ..., A24; the second pump laser beam 9 located in the inner ring has 16 reflection areas on the parabolic reflector, which are respectively recorded as B1, B2, ..., B16.

[0057] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A multi-pump source disk laser pump cavity structure, comprising a proximal end and a distal end, characterized in that: include: Two groups of pump laser beams, two groups of beam collimators, two groups of parabolic reflector groups, one laser gain medium, and two groups of deflection optical prism groups, wherein the wavelengths of the pump laser beams are all within the absorption spectrum of the laser gain medium; The laser gain medium includes a medium reflection surface, and the parabolic reflector group is provided with a plurality of reflection curved surfaces, and the reflection curved surfaces are all parabolic; The pump laser beams at the proximal end are respectively passed through a beam collimator and then incident on the parabolic reflector group at the distal end, so as to undergo multiple reflections between a deflection optical prism group, a reflective curved surface, and a medium reflective surface, and pass through the laser gain medium multiple times to be absorbed by the laser gain medium and form a pump light spot; The deflection optical prism groups are all coaxial annular structures composed of multiple prism pairs, each of which includes two prisms, and both prisms have reflection planes that form a 90° angle with each other; the reflection planes of all prism pairs are evenly distributed in an annular shape toward the distal end; The two groups of pump laser beams include a first pump laser beam and a second pump laser beam, the two groups of parabolic reflector groups include a first parabolic reflector group and a second parabolic reflector group; the two groups of deflection optical prism groups include a first deflection optical prism group and a second deflection optical prism group; The first pump laser beam and the second pump laser beam have the same optical power, and the spot diameters formed by them on the laser gain medium are the same, and they overlap on the laser gain medium; The first pump laser beam, the first deflection optical prism group, and the first parabolic reflector are located in the outer ring of the pump cavity structure, and the second pump laser beam, the second deflection optical prism group, and the second parabolic reflector are located in the inner ring of the pump cavity structure; The input position of the second pump laser beam is in the inner ring, and the input position of the first pump laser beam is in the outer ring; the incident angle of the second pump laser beam on the laser gain medium is smaller than the incident angle on the laser gain medium, and the beam collimator corresponding to the second pump laser beam has a larger magnification.

2. The multi-pump source disk laser pump cavity structure according to claim 1, characterized in that: The laser gain medium and the medium reflection surface are both circular; the parabolic reflector group is a ring structure, on which a plurality of the reflection curved surfaces are arranged at equal intervals around its circumference; the medium reflection surface and the parabolic reflector group are coaxial, and the focal points of all the reflection curved surfaces on the parabolic reflector group are located on the medium reflection surface; the laser gain medium is located between the medium reflection surface and the parabolic reflector group.

3. The multi-pump source disk laser pump cavity structure according to claim 2, characterized in that: The reflective curved surfaces all have the same equivalent focal length.

4. The multi-pump source disk laser pump cavity structure according to claim 3, characterized in that: The deflection optical prism assembly includes a plane reflector or a corner cone reflector, which is used to return the incident pump laser beam along the original path.

5. The multi-pump source disk laser pump cavity structure according to claim 1, characterized in that: The reflective curved surface and the reflective flat surface are both coated with a first dielectric film having high reflectivity for the pump laser beam.

6. The multi-pump source disk laser pump cavity structure according to claim 5, characterized in that: The thickness of the laser gain medium is 0.15 to 0.35 mm, and it includes a front surface facing the parabolic reflector assembly and a rear surface facing away from the parabolic reflector assembly; the front surface is coated with a second dielectric film that increases the transmittance of the pump laser beam; and the rear surface is coated with a third dielectric film with high reflectivity for the pump laser beam to form the dielectric reflective surface.

7. The multi-pump source disk laser pump cavity structure according to claim 6, characterized in that: The laser gain medium is fixed to the heat sink by welding, gluing or bonding, and the other side of the heat sink is in contact with a jet coolant to cool the laser gain medium. The heat sink is made of tungsten copper, diamond, sapphire, silicon carbide or aluminum nitride ceramic.

8. The multi-pump source disk laser pump cavity structure according to claim 1, characterized in that: The pump laser beam has 12, 16 or 24 reflection areas on the parabolic reflector group, and the light spots of the pump laser beam on the reflection areas do not overlap.

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