End-pumped pulse laser

Abstract

The utility model provides an end-pumped pulse laser, which sequentially comprises a pumping source, a pumping beam splitting module, a laser amplification module and a seed source, the pumping source and the seed source are oppositely arranged on the same horizontal straight line, and a beam expanding lens group is further arranged between the laser amplification module and the seed source; the pumping beam splitting module comprises a plurality of pumping lenses, a plurality of pumping beam splitters and a pumping reflector, and can split a pumping source light beam into a plurality of pumping light beams with the same or different energies; the laser amplification module comprises a reflecting mirror, a laser crystal and a matching mirror which are arranged in the propagation direction of the multiple pump light beams, and further comprises a spatial optical isolator, the laser amplification module can amplify the seed laser for multiple times, and finally a high-energy single-pulse laser beam is output. The laser finally output by the pulse laser has the characteristics of narrow pulse width, high peak energy and small focusing light spot, and is more suitable for quickly, accurately and nondestructively evaluating the sensitization degree of the ship body on site.

Description

Technical Field

[0001] The utility model relates to the technical field of lasers, in particular to an end-pumped pulse laser. Background Art

[0002] 5xxx series aluminum-magnesium alloys are increasingly being considered as replacements for structural steels, particularly in marine applications. These non-heat-treatable alloys offer a high strength-to-weight ratio, good corrosion resistance, and good weldability and formability. However, 5xxx series aluminum-magnesium alloys are susceptible to sensitization, which refers to the formation of a harmful second phase at the grain boundaries caused by high temperature aging, which can cause intergranular corrosion and reduce mechanical properties.

[0003] If this alloy sensitization and embrittlement cannot be discovered and treated in time, it will seriously affect the service life of the ship. At present, the general method for evaluating the degree of alloy sensitization (DoS) is the ASTM G67-13 nitric acid mass loss test (NAMLT) technology, but this method is expensive, time-consuming and destructive. Laser induced breakdown spectroscopy (LIBS) uses high-energy pulsed lasers to focus on the surface of the sample to be tested, ablating the sample to generate plasma, and indirectly obtains the changes in the chemical composition of the alloy by analyzing the wavelength and intensity of the plasma emission spectrum. LIBS is a new technology for rapid, accurate and non-destructive on-site evaluation of the degree of sensitization of the hull surface, and has broad application prospects. Utility Model Content

[0004] The purpose of this utility model is to provide an end-pumped pulse laser, which is more suitable for rapid, accurate and non-destructive on-site assessment of the sensitization degree of the hull compared to the multi-mode Q-switched infrared laser currently used in LIBS. The specific technical solution is as follows:

[0005] An end-pumped pulse laser, the laser comprising a pump source, a pump beam splitting module, a laser amplification module, and a seed source in sequence, the pump source and the seed source being relatively arranged on the same horizontal line, and a beam expander group being further arranged between the laser amplification module and the seed source;

[0006] The pump beam splitting module includes a plurality of pump lenses, a plurality of pump beam splitters and a pump reflector, and the pump beam splitting module can split the pump source laser beam into a plurality of pump beams with the same or different energies;

[0007] The laser amplification module includes a reflector, a laser crystal and a matching mirror arranged in the propagation direction of the multiple pump light beams, and also includes a spatial optical isolator. The laser amplification module can amplify the seed source laser multiple times.

[0008] Further, the pump beam splitting module includes, in sequence, a first pump lens, a first pump beam splitter, and a second pump lens after the pump source, and also includes a second pump beam splitter and a pump reflector disposed side by side with the first pump beam splitter on one side of the horizontal straight line and in a direction perpendicular to the horizontal straight line, and also includes a third pump lens after the second pump beam splitter and a fourth pump lens after the pump reflector;

[0009] The laser amplification module includes a first reflector, a first laser crystal, a spatial light isolator and a first matching mirror after the second pump lens, and also includes a second reflector, a second laser crystal, a second matching mirror and a fourth reflector after the third pump lens, and also includes a third reflector, a third matching mirror and a third laser crystal after the fourth pump lens. The forward input end of the spatial light isolator faces the first matching mirror.

[0010] Furthermore, the pump source is a fiber-coupled semiconductor pulse laser, and the output laser wavelength of the laser is 808 nm or 878.5 nm.

[0011] Further, the focal length of the first pump lens is 20-25 mm, and the focal lengths of the second pump lens, the third pump lens and the fourth pump lens are 50-75 mm;

[0012] The pump beam splitter is a 45° partial reflection mirror, the reflection-transmission ratio of the first pump beam splitter is 3:7 or 4:6, and the reflection-transmission ratio of the second pump beam splitter is 1:1.

[0013] Further, the first reflector is a 0° high-beam dichroic mirror, the fourth reflector is a 45° high-beam dichroic mirror, and the second reflector and the third reflector are 45° high-transmittance dichroic mirrors;

[0014] The first matching mirror, the second matching mirror and the third matching mirror are infrared plano-concave lenses with a focal length of 200-500 mm;

[0015] The first laser crystal, the second laser crystal and the third laser crystal are Nd:YVO4 crystals coated with infrared anti-reflection films on both sides;

[0016] The spatial optical isolator inputs horizontal polarization in a forward direction, outputs horizontal polarization in a forward direction, inputs horizontal polarization in a reverse direction, and outputs vertical polarization in a lateral direction.

[0017] Furthermore, the beam expander set is a Galilean telescope, and the magnification of the beam expander set is 2 times / 4 times;

[0018] The seed source is a LD directly pumped passive Q-switched infrared laser, and the beam quality of the laser is less than 1.3.

[0019] The utility model provides an end-pumped pulse laser, which has the following beneficial effects:

[0020] The utility model provides an end-pump pulse laser, which can amplify the seed laser multiple times. The laser finally output has the characteristics of narrow pulse width, high peak energy and small focused spot, and is more suitable for fast, accurate and non-destructive on-site evaluation of the sensitization degree of the hull. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The utility model is a schematic diagram of the structure of an end-pumped pulse laser. DETAILED DESCRIPTION

[0022] The following will be combined with the accompanying drawings provided by the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. According to the following description, the advantages and features of the utility model will be clearer. It should be noted that the drawings are all in a very simplified form and are not in precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the utility model.

[0023] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connection" and "connected" should be interpreted in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] In the description of the present invention, terms such as "upper", "lower", "left", "right", "front", "back", "center", "horizontal", "vertical", "top", "bottom", "inside" and "outside" and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of description and simplification of operation, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0025] Embodiment 1: This embodiment provides an end-pumped pulse laser, which includes a pump source, a pump beam splitting module, a laser amplification module, and a seed source. The pump source and the seed source are relatively arranged on the same horizontal line, and a beam expander group is also arranged between the laser amplification module and the seed source. Among them, the pump beam splitting module includes multiple pump lenses, multiple pump beam splitters and a pump reflector, and the pump beam splitting module can split the pump light into multiple beams; the laser amplification module includes multiple reflectors, multiple laser crystals, multiple matching mirrors and a spatial optical isolator. After passing through the reflectors in the laser amplification module, the multiple pump light beams are respectively focused on the surfaces of multiple laser crystals, and the pump light energy is absorbed by the laser crystal; the seed source is turned on after the pump source, and the output laser beam enters the laser amplification module and is amplified multiple times, and then outputs a high-energy single pulse laser.

[0026] The following is a detailed description of an implementation of an end-pumped seed amplified pulse laser provided by the present invention. Figure 1 shown.

[0027] As a specific embodiment of the pump source, the pump source 1 is a fiber-coupled 808nm or 878.8nm semiconductor pulse laser, the fiber core diameter is 200μm or 400μm, the numerical aperture is 0.22, the maximum output single pulse energy of the pump source 1 is 120mJ, and the maximum output frequency is 1KHz.

[0028] As a specific implementation of the pump beam splitting module, the pump beam splitting module includes 4 pump lenses, 2 pump beam splitters and 1 pump reflector. The first pump lens 2 is behind the pump source 1, the first pump beam splitter 3 is behind the first pump lens 2, the second pump beam splitter 4 and the pump reflector 5 are placed on one side of the first pump beam splitter, and the connection direction of the three is perpendicular to the output direction of the pump light, the second pump lens 6 is behind the first pump beam splitter 3, the third pump lens 7 is behind the second pump beam splitter 4, and the fourth pump lens is behind the pump reflector 5.

[0029] Optionally, the pump lenses are all 808nm or 878.8nm plano-convex lenses, which can collimate the pump beam, wherein the focal length of the first pump lens 2 is 20-25mm, and the focal lengths of the second pump lens 6, the third pump lens 7 and the fourth pump lens 8 are 50-75mm.

[0030] Optionally, the pump beam splitter is a 45° partial reflector of 808nm or 878.8nm, the reflection-transmittance ratio of the first pump beam splitter 3 is 40:60 or 30:70, and the pump beam output by the pump source 1 can be transmitted and reflected to split into two pump beams with different energies, and the reflection-transmittance ratio of the second pump beam splitter 4 is 50:50, and the reflected pump beam can be transmitted and reflected to split into two pump beams with the same energy.

[0031] Optionally, the pump reflector is a 45° reflector of 808 nm or 878.8 nm, which can reflect the pump beam.

[0032] As a specific implementation of the laser amplification module, the laser amplification module includes 4 reflectors, 3 laser crystals, 3 matching mirrors and a spatial optical isolator. The first reflector 14, the second reflector 17 and the third reflector 18 are respectively arranged after the three pump lenses, the first reflector 14 is arranged in parallel with the second pump lens, the second reflector 17 and the third pump lens 7 have an angle of 45°, and are perpendicular to the placement direction of the second pump beam splitter 4, and the third reflector 18 and the fourth pump lens 8 have an angle of 45°, and are parallel to the placement direction of the third pump beam splitter 5.

[0033] The first reflector 14 is followed in sequence by the first laser crystal 13, the spatial light isolator 12, and the first matching mirror 11, with the forward input end of the spatial light isolator 12 facing the first matching mirror 11; the second reflector 17 is followed in sequence by the second laser crystal 16, the second matching mirror 15, and the fourth reflector 21, which is placed opposite to the forward input end of the spatial light isolator 12 and tilted at 45°, and is parallel to the second reflector 17; the third reflector 18 is followed in sequence by the third matching mirror 19 and the third laser crystal 20.

[0034] Optionally, the reflectors are all dichroic mirrors, the first reflector 14 is a 0° 1064nm high-transmittance dichroic mirror, the second reflector 17 and the third reflector 18 are 45° 808nm or 878.8nm high-transmittance dichroic mirrors, and the fourth reflector 21 is a 45° 1064nm high-transmittance dichroic mirror.

[0035] Optionally, the laser crystals are Nd:YVO4 crystals coated with infrared anti-reflection films on both sides, and the crystal shape is a rectangular parallelepiped.

[0036] Optionally, the matching mirrors are all infrared plano-concave lenses with a focal length of 200 to 500 nm.

[0037] Optionally, the spatial optical isolator 12 inputs horizontal polarization in the forward direction and outputs horizontal polarization in the forward direction, and inputs horizontal polarization in the reverse direction and outputs vertical polarization in the lateral direction.

[0038] As a specific implementation of the seed source, the seed source 9 is behind the first matching mirror 11 , and a beam expander lens group 10 is further arranged between the seed source 9 and the first matching mirror 11 .

[0039] Optionally, the seed source 9 is a LD directly pumped passively Q-switched infrared laser with a beam quality less than 1.3 and an output pulse width of sub-nanoseconds.

[0040] Optionally, the beam expander lens assembly 10 is a Galilean telescope, and its beam expansion factor is 2 times / 4 times.

[0041] Embodiment 2: This embodiment provides an end-pumped pulse laser amplification method. The method is based on an end-pumped pulse laser provided in the above embodiment 1. The method specifically includes the following steps:

[0042] S1, the pump source is turned on before the seed source, and the pump beam is collimated and parallelized by the pump lens;

[0043] S2, the pump beam is split into multiple pump beams with different energies after passing through the pump beam splitting module;

[0044] S3, multiple pump beams are input into the laser amplification module and focused onto the surfaces of multiple laser crystals respectively, and the energy of the pump beams is absorbed by the laser crystals;

[0045] S4, the seed source starts to output the laser beam, which enters the laser amplification module after being expanded by the beam expander. The laser beam is amplified multiple times before being output.

[0046] A specific implementation of step S1 in the above method: the pump source is turned on 250μs before the seed source, and outputs a pump beam with a single pulse energy of 100mJ and a frequency of 1KHz. The pump beam is collimated and parallelized by a first pump lens with a focal length of 20mm, and the focal spot size of the pump beam is 6mm.

[0047] An optional implementation of step S2 in the above method: the pump beam enters the pump beam splitting module, passes through the first pump beam splitter and the second pump beam splitter, and is split into three pump beams with energies of 40mJ, 30mJ, and 30mJ respectively. The pump beams continue to pass through a pump lens with a focal length of 60mm to be collimated and parallel.

[0048] An optional implementation of step S3 in the above method: three pump light beams enter the laser amplification module, pass through the first reflector, the second reflector, and the third reflector respectively, and then are focused onto the surface of the laser crystal. At this time, the focal spots of the three pump light beams are approximately 1.1 to 1.2 mm, and 85% of the energy of the pump light beams is absorbed by the laser crystal. After absorbing the pump light, the neodymium ions in the laser crystal transition to a high energy level, so that the energy storage of the laser crystal is approximately 30 mJ, 25 mJ, and 25 mJ, respectively.

[0049] An optional implementation of step S4 in the above method: 250μs after the pump light is turned on, the seed source is turned on, and the output beam parameter product is a horizontally polarized laser beam of 0.2mm×2mrad, the pulse width is 1.5, the energy is about 150uJ, and the frequency is 1KHz. The laser beam first enters the laser amplification module after being expanded by a beam expander, and then passes through the spatial optical isolator in the forward direction after passing through the first matching mirror, and then passes through the first laser crystal, and is amplified to 600uJ for the first time in the first laser crystal; after being reflected by the first reflector, it passes through the first laser crystal for the second time and is amplified to 1.8mJ for the second time. After that, the twice-amplified laser signal passes through the spatial isolator in the reverse direction and is output from the side, and after being reflected by the fourth reflector, it passes through the second matching mirror, and then passes through the second laser crystal and is amplified to 5mJ for the third time; after passing through the second reflector and the third reflector placed perpendicularly to each other, it passes through the third matching mirror, and then passes through the third laser crystal and is amplified to 11mJ for the fourth time. Finally, the seed laser beam is amplified four times to output a near-fundamental mode laser beam with a single pulse energy of 11mJ, a frequency of 1kHz, and a pulse width of 1.5.

[0050] The reflection-transmission ratio of the first pump beam splitter is 40:60, and the reflection-transmission ratio of the second pump beam splitter is 30:30.

[0051] The focal length of the matching mirror is 200mm. The matching mirror ensures that the beam parameter product BPP of the seed light when entering the laser crystal always remains at 0.4mm×1mrad, and the spot diameter always remains between 0.8mm-0.9mm, so that the seed light can achieve a high degree of matching with the pump light no matter how many times it is amplified, so that the energy storage of the laser crystal can be maximized.

[0052] The doping concentration of neodymium ions in the laser crystal is 0.6 at%, and the size is 4×4×20 mm.

[0053] The focal lengths of the concave and convex mirrors of the beam expander are 25mm and 50mm.

[0054] Those skilled in the art should understand that the present invention can be implemented in many other specific forms without departing from the spirit and scope of the present invention, and all other embodiments obtained by ordinary technicians in this field without making any creative work based on the embodiments of the present invention shall fall within the scope of protection of the present invention.

Claims

1. An end-pumped pulse laser, characterized in that: The laser comprises a pump source, a pump beam splitting module, a laser amplification module, and a seed source in sequence. The pump source and the seed source are relatively arranged on the same horizontal line, and a beam expander group is also arranged between the laser amplification module and the seed source. The pump beam splitting module includes a plurality of pump lenses, a plurality of pump beam splitters and a pump reflector, and the pump beam splitting module can split the pump source laser beam into a plurality of pump beams with the same or different energies; The laser amplification module includes a reflector, a laser crystal and a matching mirror arranged in the propagation direction of the multiple pump light beams, and also includes a spatial optical isolator. The laser amplification module can amplify the seed source laser multiple times.

2. The end-pumped pulse laser according to claim 1, characterized in that: The pump beam splitting module includes a first pump lens, a first pump beam splitter, and a second pump lens in sequence after the pump source, and also includes a second pump beam splitter and a pump reflector arranged side by side with the first pump beam splitter on one side of the horizontal straight line and in a direction perpendicular to the horizontal straight line, and also includes a third pump lens after the second pump beam splitter and a fourth pump lens after the pump reflector; The laser amplification module includes a first reflector, a first laser crystal, a spatial light isolator and a first matching mirror after the second pump lens, and also includes a second reflector, a second laser crystal, a second matching mirror and a fourth reflector after the third pump lens, and also includes a third reflector, a third matching mirror and a third laser crystal after the fourth pump lens. The forward input end of the spatial light isolator faces the first matching mirror, and the fourth reflector faces the forward input end of the spatial light isolator.

3. The end-pumped pulse laser according to claim 2, characterized in that: The pump source is a fiber-coupled semiconductor pulse laser, and the output laser wavelength of the laser is 808 nm or 878.5 nm.

4. The end-pumped pulse laser according to claim 2, characterized in that: The focal length of the first pump lens is 20-25 mm, and the focal lengths of the second pump lens, the third pump lens and the fourth pump lens are 50-75 mm; The pump beam splitter is a 45° partial reflection mirror, the reflection-transmission ratio of the first pump beam splitter is 3:7 or 4:6, and the reflection-transmission ratio of the second pump beam splitter is 1:

1.

5. The end-pumped pulse laser according to claim 2, characterized in that: The first reflector is a 0° high-beam dichroic mirror, the fourth reflector is a 45° high-beam dichroic mirror, and the second reflector and the third reflector are 45° high-transmittance dichroic mirrors; The first matching mirror, the second matching mirror and the third matching mirror are infrared plano-concave lenses with a focal length of 200-500 mm; The first laser crystal, the second laser crystal and the third laser crystal are Nd:YVO4 crystals coated with infrared anti-reflection films on both sides; The spatial optical isolator inputs horizontal polarization in a forward direction, outputs horizontal polarization in a forward direction, inputs horizontal polarization in a reverse direction, and outputs vertical polarization in a lateral direction.

6. The end-pumped pulse laser according to claim 1, characterized in that: The beam expander set is a Galilean telescope, and the magnification of the beam expander set is 2 times / 4 times; The seed source is a LD directly pumped passive Q-switched infrared laser, and the beam quality of the laser is less than 1.3.

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