High-repetition-rate 660 nm all-solid-state red laser

Abstract

The application provides a high-repetition-frequency 660nm all-solid-state red laser, which comprises a first light path, a second light path and at least one Pockels cell, a main cavity mirror and a first gain module are sequentially arranged on the first light path, a second gain module, an acousto-optic Q-switching device and a frequency doubling structure are sequentially arranged on the second light path, the frequency doubling structure comprises a KTP frequency doubling crystal and an output mirror, a dichroic mirror is arranged between the acousto-optic Q-switching device and the KTP frequency doubling crystal, the Pockels cell is arranged between the first gain module and the second gain module, and the two gain modules, the Pockels cell, the acousto-optic Q-switching device and the main cavity mirror form a main structure of the laser. The two gain modules are utilized, two Pockels cells are adopted to split 1064nm, 1338nm and 1319nm, after a single 1319nm wavelength is obtained, 660nm laser can be obtained through the acousto-optic Q-switching technology and the intracavity frequency doubling technology.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and more particularly to a high repetition rate 660nm all-solid-state red laser. Background Technology

[0002] As one of the important wavelengths of visible light, 660nm red laser has significant applications and enormous development potential in fields such as laser color display, laser printing, and laser medicine, and is receiving increasing attention. In laser display, red light, as one of the three primary colors, plays an irreplaceable role. Currently, the technology for generating green light, another of the three primary colors, is relatively mature, enabling high-power, high-quality green light output; therefore, research on red light is crucial. Furthermore, compared to 671nm red light, 660nm red light has a larger visual function in the human eye. The human eye is more than twice as sensitive to 660nm red light as to 671nm red light, making 660nm red lasers more suitable for applications in laser color displays. In laser medicine, due to the selective absorption of laser wavelengths by human tissues, red lasers near the 660nm band have strong penetration capabilities in the blood. Normal skin tissue and blood absorb very little red light, with most of it being absorbed by melanin and other tissues, resulting in less bleeding. Therefore, red lasers are widely used to treat skin pigmentation disorders, chronic inflammation, and endocrine disorders. In laser applications, 660nm red light can be used to pump LiTaO3:Cr. 3+ The crystal, capable of producing a 901.6nm laser output, can also serve as a pump source for crystals such as Cr:LiSAF and Cr:LiCAF. Therefore, the 660nm red pulsed laser has significant research value and promising market prospects in various fields.

[0003] A 660nm laser is typically obtained by frequency doubling the 1319nm light output from an Nd:YAG laser using KTP. However, Nd:YAG crystals face competition from other wavelengths in the 1.3μm band. Besides the common 1064nm, lasers in the 946nm, 1338nm, and 1319nm bands can also be generated. However, 946nm is a three-level system with a high threshold, making it difficult to oscillate at room temperature. While the stimulated emission cross-sections of 1338nm and 1319nm are very similar and they share a common upper laser level, 1319nm oscillates more easily than 1338nm, meaning its oscillation threshold is relatively low. Other fluorescence lines have relatively higher oscillation thresholds and are essentially non-competitive, so they are ignored here. Therefore, in experiments, researchers attempted to obtain a single 1319nm laser output using a coating method. However, because the wavelengths of 1319nm and 1338nm are quite similar, conventional coatings are no longer suitable; custom coatings are required, resulting in higher costs. In addition, inserting a standard etalon or a dispersive prism can also achieve 1.3μm laser output, but this increases the intracavity laser loss, is not conducive to the straight short cavity structure, and is very complicated. Moreover, if only measures are taken to suppress the 1064nm oscillation, a single 1319nm laser output still cannot be obtained. Summary of the Invention

[0004] In response to the aforementioned technical problems, a high repetition rate 660nm all-solid-state red laser is provided.

[0005] The technical means employed in this invention are as follows:

[0006] A high repetition rate 660nm all-solid-state red laser includes: a first optical path, a second optical path, and at least one Perimeter Broca prism. The first optical path is sequentially provided with a main cavity mirror and a first gain module. The second optical path is sequentially provided with a second gain module, an acousto-optic Q-switching device, and a frequency doubling structure. The frequency doubling structure includes a KTP frequency doubling crystal and an output mirror. A dichroic mirror is disposed between the acousto-optic Q-switching device and the KTP frequency doubling crystal. The Perimeter Broca prism is disposed between the first gain module and the second gain module. The two gain modules, the Perimeter Broca prism, the acousto-optic Q-switching device, and the main cavity mirror constitute the main structure of the laser.

[0007] Furthermore, there are two Perimbroca prisms, namely Perimbroca prism I and Perimbroca prism II, and the first gain module, Perimbroca prism I, Perimbroca prism II and the second gain module are arranged sequentially in the optical path direction.

[0008] Furthermore, the first gain module is an Nd:YAG laser module I, and the second gain module is an Nd:YAG laser module II. The gain medium of both the first gain module and the second gain module is an Nd:YAG crystal with a crystal aperture of 2-3 mm.

[0009] Furthermore, the Nd:YAG crystal is three-dimensionally pumped, with the two gain modules pumped in opposite directions, 90° out of phase.

[0010] Furthermore, the three-dimensional pump includes an Nd:YAG crystal rod, cooling water, a quartz tube, a diffuse reflection cavity, and an LD array. The Nd:YAG crystal rod is located at the center, and the quartz tube is wrapped around the outside of the Nd:YAG crystal rod. Cooling water is provided between the outside of the Nd:YAG crystal rod and the quartz tube. A diffuse reflection cavity is provided outside the quartz tube, and an LD array is provided around the outside of the diffuse reflection cavity along the circumferential direction. The LD array includes multiple bars.

[0011] Furthermore, the plurality of bar strips are staggered in the circumferential direction along the axial direction of the Nd:YAG crystal rod, and the length of the Nd:YAG crystal rod is at least three times the length of the bar strip. Two bars in the same axial direction form a one-dimensional pump line array, and the distance between the two bars is 2 mm.

[0012] Furthermore, the dichroic mirror is a crescent mirror, with a 0° 1319nm antireflection coating on its left end and a 0° 1319nm antireflection 660nm high reflectivity coating on its right end.

[0013] Furthermore, the output mirror is a dichroic mirror, employing a 0° 1319nm high-reflectivity / 660nm anti-reflection output mirror.

[0014] Furthermore, both the main cavity mirror and the output mirror are convex mirrors.

[0015] Furthermore, the repetition rate of the laser is 10-20 kHz.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] The high-repetition-rate 660nm all-solid-state red laser provided by this invention uses two identical LD ​​side-pumped Nd:YAG crystal rods connected in series and two Perinbroka prisms to form a folded cavity, thereby splitting the 1064nm, 1338nm and 1319nm wavelengths. After obtaining a single 1319nm wavelength, the 660nm laser is obtained through acousto-optic Q-switching and intracavity frequency doubling techniques.

[0018] Based on the above reasons, this invention can be widely applied in fields such as laser color display, laser printing, and laser medicine. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the optical path of the present invention.

[0021] Figure 2 This is a schematic diagram of the pumping of the two gain modules of the present invention, wherein (a) is a schematic diagram of the pumping of the first gain module and (b) is a schematic diagram of the pumping of the second gain module.

[0022] Figure 3 This is a schematic diagram of the three-dimensional pump bar of the present invention.

[0023] In the diagram: 1. Main cavity mirror; 2. Nd:YAG laser module I; 3. Perinbroca prism I; 4. Perinbroca prism II; 5. Nd:YAG laser module II; 6. Acousto-optic Q-switching device; 7. Dichroic mirror; 8. KTP frequency doubling crystal; 9. Output mirror;

[0024] 100, Nd:YAG crystal rod; 200, cooling water; 300, quartz tube; 400, diffuse reflection cavity; 500, LD array; 600, bar. Detailed Implementation

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0028] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0029] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0030] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0031] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0032] This invention provides a high repetition rate 660nm all-solid-state red laser, which is a high repetition rate 1319nm single-wavelength laser, and obtains 660nm laser by KTP intracavity frequency doubling.

[0033] This invention discloses a high-repetition-rate 660nm all-solid-state red laser, comprising a main laser structure and a frequency doubling structure, with two optical paths (a first optical path and a second optical path). The main laser structure includes two gain modules, two Perinbroka prisms, an acousto-optic Q-switching crystal (acousto-optic Q-switching device 6), and a main cavity mirror 1. The frequency doubling structure includes a KTP frequency doubling crystal 8 and an output mirror 9. A dichroic mirror 7 is disposed between the acousto-optic Q-switching device 6 and the KTP frequency doubling crystal 8. The output mirror 9 is also a dichroic mirror, separating the 1319nm and 660nm light beams.

[0034] The two gain modules are designated as the first gain module and the second gain module. The first gain module is an Nd:YAG laser module I2, and the second gain module is an Nd:YAG laser module II5. The two Perinbroca prisms are designated as Perinbroca prism I3 and Perinbroca prism II4. The main cavity mirror 1 and the first gain module are distributed in the first optical path. The second gain module, the acousto-optic Q-switching crystal, the dichroic mirror 7, the KTP frequency doubling crystal 8, and the output mirror 9 are distributed in the second optical path. The two Perinbroca prisms are positioned between the first gain module and the second gain module. The first gain module, Perinbroca prism I3, Perinbroca prism II4, and the second gain module are arranged sequentially in the optical path direction. The light rays pass sequentially through the main cavity mirror 1 and the first gain module to the Perinbroca prism I3. The light rays exiting the Perinbroca prism I3 pass sequentially through the second gain module, the acousto-optic Q-switching crystal, the dichroic mirror 7, the KTP frequency doubling crystal 8, and the output mirror 9, and are finally output through the output mirror 9 to obtain a 660nm laser.

[0035] This invention employs two identical LD ​​side-pumped Nd:YAG crystal rods connected in series, and uses two Perinbroka prisms to form a folded cavity, thereby splitting the 1064nm, 1338nm and 1319nm wavelengths. After obtaining a single 1319nm wavelength, a 660nm laser is obtained through acousto-optic Q-switching and intracavity frequency doubling techniques.

[0036] In a preferred embodiment, the gain medium of both gain modules of the laser is an Nd:YAG crystal with a crystal aperture of 2-3 mm. This is because a crystal aperture that is too large will result in poor beam quality, while a crystal aperture that is too small will be prone to breakage due to its poor strength, or may vibrate under the scouring of cooling water. Therefore, the crystal aperture is set to 2-3 mm.

[0037] In a preferred embodiment, the Nd:YAG crystal is three-dimensionally pumped, with two gain modules pumped in opposite directions, 90° out of phase. Figure 2As shown in (a) and (b), at high repetition rates, the pump module may cause uneven excitation within the gain medium due to thermal effects and uneven light field distribution, resulting in asymmetry or uneven energy distribution in the output spot. Reversing the second gain module changes the incident direction and superposition mode of the pump light, counteracting the uneven pumping generated by the first gain module and making the overall light field distribution more uniform in the gain medium. This adjustment helps balance the light intensity distribution in different directions, reduces energy concentration areas in the spot, and makes the spot distribution more uniform. The three-dimensional pump includes an Nd:YAG crystal rod 100, cooling water 200, a quartz tube 300, a diffuse reflection cavity 400, and an LD array 500. This structure can maximize the homogenization of the light spot. The Nd:YAG crystal rod 100 is located at the center, and the quartz tube 300 is wrapped around the Nd:YAG crystal rod 100. Cooling water 200 is between the outside of the Nd:YAG crystal rod 100 and the quartz tube 300. A diffuse reflection cavity 400 is provided outside the quartz tube 300. An LD array 500 is provided around the diffuse reflection cavity 400 along the circumferential direction. The LD array 500 includes multiple bars 600.

[0038] In a preferred embodiment, the three-dimensional pump bars 600 are staggered in the circumferential direction along the axial direction of the Nd:YAG crystal rod 100, such as... Figure 3 As shown, the length of the Nd:YAG crystal rod 100 is at least three times the length of the bar 600, which can disperse heat generation and improve thermal management.

[0039] In a preferred embodiment, the rated continuous pumping power of a single module is 300W, and the total pumping power of the two modules is 600W. Higher pumping intensities can easily cause over-radiation, parasitic oscillations, and very severe thermal effects.

[0040] As a preferred embodiment, single-bar pumps with limited power are used as much as possible to disperse the heat generation area and reduce the thermal effect. A typical rated power of a single-bar pump is 50W. Two bars 600 on the same axis form a one-dimensional pump array, with a spacing of 2mm between the two bars 600.

[0041] In a preferred embodiment, the radii of curvature of the main cavity mirror 1 and the output mirror 9 are adjusted to form a thermally stable cavity between them. Since the thermal focal lengths of both modules are relatively large, both the main cavity mirror 1 and the output mirror 9 are convex mirrors, and the specific radii of curvature need to be calculated based on the thermal lens.

[0042] In a preferred embodiment, the left end of the dichroic mirror 7 is coated with a 0° 1319nm antireflection film (an antireflection film under conditions of a wavelength of 1319nm and an incident angle of 0°), and the right end is coated with a 0° 1319nm antireflection 660nm high reflectivity film (achieving high reflection at a 0° incident angle and a wavelength of 1319nm, while reducing transmission and increasing reflection at a wavelength of 660nm). The output mirror 9 is a 0° 1319nm high reflectivity / 660nm antireflection output mirror (achieving high reflectivity at a wavelength of 1319nm, while achieving high transmittance at a wavelength of 660nm, with an incident angle of 0°). The dichroic mirror 7 is a crescent-shaped mirror and forms a confocal unstable cavity with the output mirror 9, compressing the distance between the dichroic mirror 7 and the output mirror 9 as much as possible, thereby improving the magnification of the required confocal unstable cavity.

[0043] As a preferred embodiment, two Perinbroka prisms are used between the two gain modules, which can reduce laser loss and suppress laser resonance beyond 1319nm.

[0044] As a preferred embodiment, the repetition rate of the high repetition rate 660nm laser is preferably 10-20kHz. When the repetition rate is too low, due to the accumulation of gain, superradiation and parasitic oscillation at 1064nm are likely to occur. At the same time, incomplete acousto-optic Q-switching may also occur. On the other hand, if the repetition rate is too high, the peak power of the Q-switched laser will decrease, reducing the frequency doubling efficiency.

[0045] In this invention, the 1064nm, 1338nm, and 1319nm fundamental frequency light emitted from an Nd:YAG laser crystal is split by two Perinbroka prisms to achieve a single wavelength output of 1319nm at a repetition rate above 10kHz. After obtaining the single 1319nm wavelength, a 660nm laser is obtained through acousto-optic Q-switching and intracavity frequency doubling. The system uses an acousto-optic Q-switch as the Q-switching device, which consists of an acousto-optic medium, an electro-acoustic transducer, sound-absorbing material, and a driving power supply. It operates in a traveling wave mode, which is suitable for high repetition rate Q-switching due to its fast field elimination and short switching time. KTP intracavity frequency doubling is chosen as the frequency doubling method. Intracavity frequency doubling has a much higher efficiency than external frequency doubling because the fundamental frequency light passes through the frequency doubling crystal multiple times. The system optimizes the cavity length based on the crystal thermal lensing effect, matching the laser mode inside the cavity with the mode behind the crystal thermal lens, improving the laser output efficiency and beam quality, and ensuring stable laser output.

[0046] When pump light acts on an Nd:YAG crystal, some of the energy is converted into heat, resulting in a significant axial temperature gradient within the crystal. This causes thermal stress and thermally induced refractive index changes within the crystal, ultimately forming a thermal lens. In a laser resonator, this thermal lensing effect alters the optical field distribution and mode structure, affecting the laser's resonant modes. As the focal length of the thermal lens changes, the radius of the fundamental mode in the laser gain medium also changes, and the dynamic operating characteristics of the laser resonator vary accordingly.

[0047] Based on the stability analysis of the resonant cavity using the ABCD matrix method, when the focal length f changes due to the thermal lensing effect, the spot size and phase distribution at the crystal also change accordingly. The system of this invention satisfies the cavity stability condition by adjusting the cavity length L. In the experiment, with other parameters fixed, an initial cavity length can be calculated and set based on preliminary theory at a lower pump power, since the thermal lensing effect is weaker. Then, the pump power is gradually increased while the laser output characteristics, such as output power and beam quality, are monitored in real time. When changes in output characteristics are detected, the cavity length is fine-tuned, and the changes in output are observed to find the optimal cavity length value for achieving the best output. This process is repeated until a relatively optimized cavity length can be found at different pump powers. By optimizing the cavity length, the laser mode inside the cavity can be matched with the mode behind the crystal thermal lens, reducing mode mismatch loss, increasing the spot base film size, improving laser output efficiency and beam quality, and ensuring stable laser output.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-repetition-rate 660nm all-solid-state red laser, characterized in that, include: The laser consists of a first optical path, a second optical path, and at least one Perinbroka prism. The first optical path is provided with a main cavity mirror (1) and a first gain module in sequence. The second optical path is provided with a second gain module, an acousto-optic Q-switching device (6), and a frequency doubling structure in sequence. The frequency doubling structure includes a KTP frequency doubling crystal (8) and an output mirror (9). A dichroic mirror (7) is provided between the acousto-optic Q-switching device (6) and the KTP frequency doubling crystal (8). The Perinbroka prism is located between the first gain module and the second gain module. The two gain modules, the Perinbroka prism, the acousto-optic Q-switching device (6), and the main cavity mirror (1) constitute the main structure of the laser.

2. The high repetition rate 660nm all-solid-state red laser according to claim 1, characterized in that, The Perinbroca prism is provided in two parts, namely Perinbroca prism I (3) and Perinbroca prism II (4). The first gain module, Perinbroca prism I (3), Perinbroca prism II (4) and the second gain module are arranged sequentially in the optical path direction.

3. The high repetition rate 660nm all-solid-state red laser according to claim 1, characterized in that, The first gain module is an Nd:YAG laser module I (2), and the second gain module is an Nd:YAG laser module II (5). The gain medium of both the first and second gain modules is an Nd:YAG crystal with a crystal aperture of 2-3 mm.

4. The high repetition rate 660nm all-solid-state red laser according to claim 3, characterized in that, The Nd:YAG crystal is three-dimensionally pumped, with two gain modules pumped in opposite directions, 90° out of phase.

5. The high repetition rate 660nm all-solid-state red laser according to claim 4, characterized in that, The three-dimensional pump includes an Nd:YAG crystal rod (100), cooling water (200), a quartz tube (300), a diffuse reflection cavity (400), and an LD array (500). The Nd:YAG crystal rod (100) is located at the center. The quartz tube (300) is wrapped around the outside of the Nd:YAG crystal rod (100). Cooling water (200) is between the outside of the Nd:YAG crystal rod (100) and the quartz tube (300). The diffuse reflection cavity (400) is provided outside the quartz tube (300). The LD array (500) is provided around the diffuse reflection cavity (400) along the circumferential direction. The LD array (500) includes multiple bars (600).

6. The high repetition rate 660nm all-solid-state red laser according to claim 5, characterized in that, The plurality of bar strips (600) are staggered in the circumferential direction along the axial direction of the Nd:YAG crystal rod (100). The length of the Nd:YAG crystal rod (100) is at least three times the length of the bar strips (600). Two bar strips (600) in the same axial direction form a one-dimensional pump line array, and the distance between the two bar strips (600) is 2 mm.

7. The high repetition rate 660nm all-solid-state red laser according to claim 1, characterized in that, The dichroic mirror (7) is a crescent mirror, with a 0° 1319nm anti-reflection coating on its left end and a 0° 1319nm anti-reflection 660nm high-reflection coating on its right end.

8. The high repetition rate 660nm all-solid-state red laser according to claim 1, characterized in that, The output mirror (9) is a dichroic mirror, using a 0° 1319nm high reflectivity / 660nm anti-reflection output mirror.

9. The high repetition rate 660nm all-solid-state red laser according to claim 1, characterized in that, Both the main cavity mirror (1) and the output mirror (9) are convex mirrors.

10. The high repetition rate 660nm all-solid-state red laser according to claim 1, characterized in that, The repetition rate of the laser is 10-20kHz.

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