A pump laser

Abstract

The application belongs to the technical field of optics, and specifically provides a pump laser, a high-energy laser system adopting a xenon lamp pump, a Gaussian mirror cavity, a working frequency within 100 Hz, nanosecond level and joule level electro-optic Q-switching, good long-term stability, easy maintenance and strong environmental adaptability. The high-energy laser system can effectively solve the problems of internal pollution after long-term light emission of the existing lamp-pumped narrow pulse width high-energy laser system, easy aging of the pump source under high load, difficulty in replacing the pump source after aging, easy dotting on the surface of the optical crystal, deterioration of the output light spot and existence of destructive self-laser in the internal.

Description

Technical Field

[0001] This invention belongs to the field of optical technology, and specifically relates to a pump laser. Background Technology

[0002] Lamp-pumped narrow-pulse high-energy laser systems are a core component of many laser devices, widely used in industrial processing, scientific research, medical aesthetics, analytical measurement, and many other fields. They offer irreplaceable advantages, particularly in specific applications such as laser-enhanced shock, pulsed laser deposition, lidar, particle velocimetry, mass spectrometry, laser freckle removal, and laser tattoo removal.

[0003] With the rapid development of the laser equipment industry, in order to cope with the rapid changes in the laser equipment market, laser users have also put forward higher requirements for the output indicators of laser systems, as well as the long-term stability, long-term reliability, maintainability, and environmental adaptability of lasers.

[0004] Existing lamp-pumped narrow-pulse high-energy laser systems generally suffer from the following problems: 1) internal contamination occurs after long-term laser output; 2) pulsed xenon lamps are prone to aging and failure under high loads, and are difficult to replace after aging; 3) the crystal surface of the laser is prone to spotting after long-term laser output; 4) the output beam deteriorates due to high-energy lasers; 5) the laser contains destructive self-lasing and other disadvantages.

[0005] In view of the many problems that exist in existing lamp-pumped narrow-pulse-width high-energy laser systems, this invention proposes a pump laser that can effectively solve the common problems of existing lamp-pumped narrow-pulse-width high-energy laser systems. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of internal contamination after long-term output of existing lamp-pumped narrow-pulse-width high-energy laser systems, easy spotting on the surface of the optical crystal, deterioration of the output beam, and the presence of destructive self-lasing inside.

[0007] Therefore, the present invention provides a pump laser, including a laser housing and a laser generating unit and a first-stage traveling wave amplification unit disposed within the laser housing;

[0008] The laser generating unit includes a first pump source and a reflector I, a laser switch, a first gain medium, a pinhole aperture I, and an output mirror arranged coaxially along the optical path; the first pump source provides pump excitation to the first gain medium.

[0009] The first-stage traveling-wave amplification unit includes a pinhole aperture II, a mirror II, a mirror III, a plano-concave lens II, a second pump source, a second gain medium, and a third pump source; the pinhole aperture II and the mirror II are coaxially arranged behind the output mirror; the mirror III is placed at a 90-degree angle to the mirror II; the mirror III, the plano-concave lens II, and the second gain medium are coaxially arranged; the light generated by the laser generation unit passes through the pinhole aperture II, the mirror II, the mirror III, the plano-concave lens II, and the second gain medium in sequence before being output;

[0010] The first pump source, the first gain medium, the second pump source, the second gain medium, and the third pump source are all placed in the focusing cavity, with the first gain medium positioned between the first pump source and the second pump source; and the second gain medium positioned between the second pump source and the third pump source.

[0011] Specifically, the two ends of the second gain medium are parallel and have an inclination angle θ; the inclination angle θ is calculated by the formula θ=(1 / 2)arctan(d / L2); where d is the aperture of the pinhole aperture II and L2 is the distance from the center of the aperture of the pinhole aperture I to the center of the front end face of the second gain medium.

[0012] Specifically, the aforementioned laser generating unit further includes a plano-concave lens I and a plano-convex lens arranged coaxially along the optical path direction; the plano-concave lens I is disposed between the first gain medium and the pinhole aperture I, and the plane of the plano-concave lens I faces the rear end face of the first gain medium; the plano-convex lens is disposed between the pinhole aperture I and the output mirror, and the convex surface of the plano-convex lens faces the concave surface of the plano-concave lens I.

[0013] Specifically, the formula for calculating the distance L4 between the vertex of the concave surface of the plano-concave lens I and the vertex of the convex surface of the plano-convex lens is L4 = R3 / 2 + R2 / 2 + ΔL; where R2 is the curvature of the concave surface of the plano-concave lens I, R3 is the curvature of the convex surface of the plano-convex lens, and ΔL is the preset adjustment amount for adjusting the size of the output light spot and the divergence angle.

[0014] Specifically, the output mirror mentioned above is a double-sided Gaussian mirror with curvature.

[0015] Specifically, the formula for calculating the focal length R4 of the side of the Gaussian mirror facing the convex surface of the plano-convex lens is R4=[(R2 / 2)+ΔL]×(R2 / 2)÷ΔL-L5; where R2 is the concave curvature of the plano-convex lens I, ΔL is the preset adjustment amount for adjusting the size of the output spot and the divergence angle, and L5 is the distance from the center of the output mirror to the center of the plano-convex lens plane; the focal length of the other side of the Gaussian mirror is -R4.

[0016] Specifically, the first, second, and third pump sources mentioned above are all laser pulse xenon lamps; the pumping method of the pump laser is multi-lamp series or multi-lamp parallel side-pumping of a single gain medium.

[0017] Specifically, the aforementioned reflector I is a single-sided coated zero-degree total reflection mirror, and the coated surface is convex; the front end of the first gain medium is provided with an equivalent thermal lens; the formula for calculating the convex curvature R1 of the reflector I is R1=2×(f T7 -L1) where, f T7 L1 is the focal length of the equivalent thermal lens of the first gain medium, and L2 is the distance from the vertex of the convex surface of mirror I to the center of the front end surface of the first gain medium.

[0018] Specifically, the aforementioned laser switch includes a waveplate, a Q-switch, and a polarizer arranged coaxially along the optical path.

[0019] Specifically, the laser housing is further provided with an air pump and a filter; the air pump inlet is connected to the inside of the laser housing; the air pump outlet is connected to the air filter inlet; and the filter outlet is connected to the inside of the laser housing.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] The pumped laser provided by this invention is a high-energy laser system employing xenon lamp pumping, a Gaussian cavity, and operating frequencies within 100 Hz, with nanosecond-level and joule-level electro-optic Q-switching. It exhibits good long-term stability, ease of maintenance, and strong environmental adaptability. It effectively solves the problems of existing lamp-pumped narrow-pulse-width high-energy laser systems, such as internal contamination after long-term output, easy aging and failure of the pump source under high load, difficulty in replacement after aging, easy spotting on the optical crystal surface, deterioration of the output beam, and destructive self-lasing.

[0022] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the pump laser provided by the present invention.

[0024] Figure 2 This is an optical schematic diagram of the pump laser provided by the present invention.

[0025] Reference numerals: 1. Mirror I; 2. Waveplate; 3. Q-switch; 4. Polarizer; 5. Concentrating cavity; 6. First pump source; 7. First gain medium; 8. Plano-concave lens I; 9. Plano-convex lens; 10. Pinhole stop I; 11. Output mirror; 12. Mirror II; 13. Pinhole stop II; 14. Mirror III; 15. Plano-concave lens II; 16. Second pump source; 17. Second gain medium; 18. Third pump source; 19. Air pump; 20. Filter. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Although representative embodiments of the present invention have been described in detail, those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the embodiments, but should be defined by the appended claims and their equivalents. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature; in the description of the invention, unless otherwise stated, "a plurality of" means two or more.

[0027] Reference Figure 1-2 This invention provides a pumped laser, comprising a laser housing and a laser generating unit and a first-stage traveling-wave amplification unit disposed within the laser housing; the laser generating unit includes a first pump source 6 and a mirror I1, a laser switch, a first gain medium 7, a pinhole aperture I10, and an output mirror 11 arranged coaxially along the optical path; the first pump source 6 provides pump excitation to the first gain medium 7; the first-stage traveling-wave amplification unit includes a pinhole aperture II13, a mirror II12, a mirror III14, a plano-concave lens II15, a second pump source 16, a second gain medium 17, and a third pump source 18; the pinhole aperture II13 is arranged coaxially after the output mirror 11. The laser generating unit consists of a reflector II 12 and a reflector III 14 placed at a 90-degree angle to reflector II 12. The reflector III 14, the plano-concave lens II 15, and the second gain medium 17 are arranged coaxially. The light generated by the laser generating unit passes sequentially through the pinhole aperture II 13, the reflector II 12, the reflector III 14, the plano-concave lens II 15, and the second gain medium 17 before being output. The first pump source 6, the first gain medium 7, the second pump source 16, the second gain medium 17, and the third pump source 18 are all placed in the focusing cavity 5, with the first gain medium 7 positioned between the first pump source 6 and the second pump source 16. The second gain medium 17 is positioned between the second pump source 16 and the third pump source 18.

[0028] Among them, the reflector I1 is a zero-degree total reflection mirror with a single-sided coating, and the coating surface is convex. The front end surface of the first gain medium 7 is provided with an equivalent thermal lens; the formula for calculating the convex curvature R1 of the reflector I1 is as follows:

[0029] R1=2×(f T7 -L1)

[0030] Among them, f T7L1 is the focal length of the equivalent thermal lens of the first gain medium 7, and L2 is the distance from the vertex of the convex surface of the mirror I1 to the center of the front end face of the first gain medium 7.

[0031] Furthermore, the laser switch includes a waveplate 2, a Q-switch 3, and a polarizer 4 arranged coaxially along the optical path. The waveplate 2 is preferably a λ / 4 waveplate with a phase delay accuracy higher than λ / 300, and is placed immediately behind the convex surface of the reflector I1. The Q-switch 3 is preferably a KD*P electro-optic Q-switch, placed immediately behind the waveplate 2, and has a voltage extinction ratio higher than 1500:1. The polarizer 4 is preferably a horizontal polarizer, placed immediately behind the Q-switch 3, and has a polarization ratio exceeding 1000:1. The polarization angle of the polarizer 4 can be selected as 45 degrees or 56 degrees. The laser switch composed of the waveplate 2, Q-switch 3, and polarizer 4 has a laser switching capability of 0.5 J or more within 50 Hz.

[0032] To eliminate destructive self-lasing within the laser and improve the effective energy storage utilization of the gain medium, the two end faces of the second gain medium 17 are parallel and have a tilt angle θ; the formula for calculating the tilt angle θ is as follows:

[0033]

[0034] Where d is the aperture of pinhole aperture II 13, and L2 is the distance from the center of the aperture of pinhole aperture I 10 to the center of the front end face of the second gain medium 17.

[0035] Preferably, the first gain medium 7 and the second gain medium 17 are NdYAG crystal rods. The first pump source 6, the second pump source 16, and the third pump source 18 are laser pulse xenon lamps, made of high-quality UV-filtering quartz glass tubes, with electrodes made of high-density molybdenum. The internal xenon gas is encapsulated using transition glass encapsulation technology, with an arc length the same as the length of the gain medium and an outer diameter the same as the diameter of the gain medium. The pumping method of the pump sources is multi-lamp series or multi-lamp parallel side-pumping of a single gain medium. Compared to single-lamp pumping single-lamp or single-lamp pumping multiple rods, the lifespan of the xenon lamp can be increased exponentially. The formula for calculating the number of flashes N of the xenon lamp is:

[0036]

[0037] Among them, E x The explosion energy of a xenon lamp is constant, k is a constant coefficient, typically around 4 to 8, and E O This refers to the energy injected into the xenon lamp. As shown in the formula above, using a dual-lamp pump to power a single lamp increases the xenon lamp's lifespan by 2% compared to a single-lamp pump to power a single lamp. (4 / 8) times.

[0038] Furthermore, the focusing cavity 5, which houses the pump source and gain medium, is preferably a combined water-cooled gold-plated cavity. The cavity type is a multi-lamp, multi-rod cavity with a separate lamp and rod structure. The number of lamps is one more than the number of rods. The lamps and rods are alternately placed from left to right in a lamp-rod-lamp-rod-lamp configuration. The axial spacing between the lamps and rods is twice the diameter of the crystal rod. The lamps and rods are placed in odd-numbered and even-numbered positions, respectively. Each rod has one lamp on each side to ensure uniform pumping. The reflector surface inside the focusing cavity 5 is gold-plated, achieving a reflectivity of over 98% in the 400nm-1200nm spectral range. The length of the reflector is the same as the length of the crystal rod, and the width and height of the reflector are calculated using the following formulas:

[0039] The width of the reflector = the diameter of the crystal rod × (twice the number of crystal rods + twice the number of xenon lamps - 1);

[0040] The height of the reflector = the diameter of the crystal rod × 3

[0041] In a detailed embodiment, the aperture 110 and aperture 213 are made of polysulfone material, which has strong radiation resistance. The aperture d of aperture 110 and aperture 213 is equal to the diameter of the NdYAG crystal rod.

[0042] Furthermore, the laser generating unit also includes a plano-concave lens I8 and a plano-convex lens 9 arranged coaxially along the optical path direction; the concave curvature R2 of the plano-concave lens I8 is generally -30mm, and it is positioned between the first gain medium 7 and the pinhole aperture I10, placed close to the rear end face of the first gain medium 7, and the plane of the plano-concave lens I8 faces the rear end face of the first gain medium 7; the convex curvature R3 of the plano-convex lens 9 is generally between 90mm and 120mm, and it is positioned between the pinhole aperture I10 and the output mirror 11, and the convex surface faces the concave surface of the plano-concave lens I8.

[0043] The formula for calculating the distance L4 between the vertex of the concave surface of plano-concave lens I8 and the vertex of the convex surface of plano-convex lens 9 is as follows:

[0044]

[0045] Where ΔL is a preset adjustment value, typically ± a few mm. Changing ΔL adjusts the size and divergence angle of the output light spot. The changes in the output light spot size Δd and the divergence angle Δθ are calculated using the following formulas:

[0046] Δd=2×d×ΔL÷R2

[0047]

[0048] A plano-convex lens 9 and a plano-concave lens I 8 form a Galilean telescope to prevent reflected light from damaging the laser crystal due to incomplete transmission from the plano-convex lens 9 and plano-concave lens I 8. The magnification of the telescope composed of plano-concave lens I 8 and plano-convex lens 9 is equal to the depolarization depth of the output beam from the resonant cavity. Due to the thermal effect of the NdYAG crystal rod, the laser accumulates a large amount of thermal depolarization within the resonant cavity before exiting, causing the output beam to gradually change from a circle to a quadrilateral. The depolarization depth is defined as the reciprocal of the ratio of the radius of the largest circle that can be drawn with the geometric center of the output beam as the origin to the radius of the NdYAG crystal rod.

[0049] Furthermore, the output mirror 11 is a double-sided Gaussian mirror with curvature, placed behind the plano-convex lens 9. The distance from the center of the output mirror 11 to the center of the plane of the plano-convex lens 9 is L5. The formula for calculating the focal length R4 of the convex side of the Gaussian mirror facing the plano-convex lens 9 is as follows:

[0050]

[0051] Where R2 is the concave curvature of the plano-concave lens I8, ΔL is the preset adjustment amount for adjusting the output spot size and divergence angle, and L5 is the distance from the center of the output mirror 11 to the center of the plane of the plano-convex lens 9; the focal length of the other side of the Gaussian mirror is -R4. Using a Gaussian mirror instead of a regular mirror can change the energy distribution of the output spot from a Gaussian distribution to a uniform distribution, greatly reducing the peak power density at the center of the output spot. This can increase the output energy by 3 to 5 times without damaging the crystal and lens or increasing their size. The Gaussian mirror can be coated with a film with gradually changing reflectivity radially from the center of the lens. The center reflectivity is 15% to 35%, and the edge reflectivity is twice that of the center. The coating radius is the radial distance from the center reflectivity to the edge reflectivity, and is the same as the diameter of the NdYAG crystal rod.

[0052] Furthermore, reflectors II12 and III14 are 45-degree reflectors, and the center distance between reflector II12 and pinhole aperture II13 is L6.

[0053] Furthermore, the plano-concave lens II 15 is placed close to the front end face of the second gain medium 17, and the plane of the plano-concave lens II 15 faces the front end face of the second gain medium 17. Preferably, the second gain medium 17 is an NdYAG crystal rod, and its front end face is provided with an equivalent thermal lens. The focal length of the plano-concave lens II 15 is equal to the thermal focal length f of the equivalent thermal lens. T17 The difference between the length of the laser pulse xenon lamp electrode and the total length of the laser pulse xenon lamp electrode is half the difference between the total length and the arc length.

[0054] Furthermore, the second gain medium 17 is placed behind the reflector III 14, and the distance from the front end face of the second gain medium 17 to the center of the reflector III 14 is defined as L7.

[0055] Furthermore,

[0056]

[0057] Where d is the aperture of the pinhole aperture II 13; θ is the tilt angle of the end face of the second gain medium 17.

[0058] To control internal contamination generated after prolonged laser emission, an air filtration system consisting of an air pump 19 and a filter 20 is installed inside the laser housing. The air inlet of the air pump 19 is connected to the interior of the laser housing; the air outlet of the air pump 19 is connected to the air inlet of the filter 20; and the air outlet of the filter 20 is connected to the interior of the laser housing. The air pump 19 draws air from inside the laser housing and sends it to the filter 20 for filtration. After being processed by the filter 20, the air is directly returned to the laser housing. This air filtration system can efficiently remove water molecules, organic gas molecules, and solid particles larger than 0.3 μm from the laser cavity, maintaining the cleanliness inside the laser housing and significantly improving the lifespan of the laser device and the laser itself.

[0059] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A pumped laser, comprising a laser housing and a laser generating unit and a first-stage traveling-wave amplification unit disposed within the laser housing; characterized in that: The laser generating unit includes a first pump source and a reflector I, a laser switch, a first gain medium, a pinhole aperture I, and an output mirror arranged coaxially along the optical path. The first pump source provides pump excitation to the first gain medium. The reflector I is a single-sided coated zero-degree total reflection mirror with a convex coating. The front end of the first gain medium is provided with an equivalent thermal lens. The formula for calculating the convex curvature R1 of the reflector I is: ; Among them, f T7 L1 is the focal length of the equivalent thermal lens of the first gain medium, and L2 is the distance from the vertex of the convex surface of mirror I to the center of the front end surface of the first gain medium. The first-stage traveling-wave amplification unit includes a pinhole aperture II, a mirror II, a mirror III, a plano-concave lens II, a second pump source, a second gain medium, and a third pump source; the pinhole aperture II and the mirror II are coaxially arranged behind the output mirror; the mirror III is placed at a 90-degree angle to the mirror II; the mirror III, the plano-concave lens II, and the second gain medium are coaxially arranged; the light generated by the laser generation unit passes through the pinhole aperture II, the mirror II, the mirror III, the plano-concave lens II, and the second gain medium in sequence before being output; The first pump source, the first gain medium, the second pump source, the second gain medium, and the third pump source are all placed in a focusing cavity. The focusing cavity is a multi-lamp, multi-rod cavity, with the lamp rod axis spacing being twice the diameter of the crystal rod, and one lamp on each side of each rod. The surface of the reflector inside the focusing cavity is gold-plated. The length of the reflector is the same as the length of the crystal rod, the width of the reflector = the diameter of the crystal rod × (twice the number of crystal rods + twice the number of xenon lamps - 1), and the height of the reflector = the diameter of the crystal rod × 3. The first gain medium is placed between the first pump source and the second pump source. The second gain medium is placed between the second pump source and the third pump source.

2. The pump laser as described in claim 1, characterized in that: The two ends of the second gain medium are parallel and have an inclination angle θ; the inclination angle θ is calculated by the formula θ=(1 / 2)arctan (d / L2); where d is the aperture of the pinhole aperture II and L2 is the distance from the center of the aperture of the pinhole aperture I to the center of the front end face of the second gain medium.

3. The pump laser as described in claim 1, characterized in that: The laser generating unit further includes a plano-concave lens I and a plano-convex lens arranged coaxially along the optical path direction; the plano-concave lens I is disposed between the first gain medium and the pinhole aperture I, and the plane of the plano-concave lens I faces the rear end face of the first gain medium; the plano-convex lens is disposed between the pinhole aperture I and the output mirror, and the convex surface of the plano-convex lens faces the concave surface of the plano-concave lens I.

4. The pump laser as described in claim 3, characterized in that: The formula for calculating the distance L4 between the vertex of the concave surface of the plano-concave lens I and the vertex of the convex surface of the plano-convex lens is as follows: Where R2 is the concave curvature of the plano-concave lens I, and R3 is the convex curvature of the plano-convex lens. The preset adjustment amount is used to adjust the output spot size and divergence angle.

5. The pump laser as described in claim 3, characterized in that: The output mirror is a double-sided Gaussian mirror with curvature.

6. The pump laser as described in claim 5, characterized in that: The formula for calculating the focal length R4 of the side of the Gaussian mirror and the plano-convex lens facing each other is as follows: Where R2 is the concave curvature of the plano-concave lens I. To adjust the preset adjustment amount of the output spot size and divergence angle, L5 is the distance from the center of the output mirror to the center of the plano-convex lens plane; the focal length of the other side of the Gaussian mirror is -R4.

7. The pump laser as claimed in claim 1, characterized in that: The first pump source, the second pump source, and the third pump source are all laser pulse xenon lamps; the pumping method of the pump laser is multi-lamp series or multi-lamp parallel side-pumping of a single gain medium.

8. The pump laser as described in claim 1, characterized in that: The laser switch includes a waveplate, a Q-switch, and a polarizer arranged coaxially along the optical path.

9. The pump laser as claimed in claim 1, characterized in that: The laser housing is also equipped with an air pump and a filter; the air inlet of the air pump is connected to the inside of the laser housing; the air outlet of the air pump is connected to the air inlet of the filter; and the air outlet of the filter is connected to the inside of the laser housing.

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