Composite pulse laser device

Abstract

The invention relates to the technical field of laser pulses, in particular to a composite pulse laser device which comprises an output mirror, a polaroid, a laser gain module, a first reflecting mirror, a first Q switch, a second reflecting mirror, a second Q switch and a controller. A second reflecting mirror, a second Q switch, a polaroid and an output mirror form a second pulse laser resonance arm cavity, the polaroid transmits the first-direction polarized laser and reflects the second-direction polarized laser, and laser of tens of nanoseconds and hundreds of nanoseconds is output from the laser gain module and the output mirror. The pulse laser output of the first pulse laser resonance arm cavity and the second pulse laser resonance arm cavity is controlled through the controller, flexible adjustment of pulse intervals is achieved, the structure is compact, design is flexible, laser output of tens of nanoseconds and laser output of hundreds of nanoseconds can be achieved at the same time under the control of the same electric signal, and high practicability is achieved.

Description

Technical Field

[0001] The invention relates to the field of laser pulse technology, in particular to a composite pulse laser device. Background Art

[0002] Large-energy Q-switched solid-state lasers with nanosecond pulse widths have the advantages of compact structure and low cost, and are widely used in laser processing, nonlinear optics, material preparation, laser ranging, laser three-dimensional scanning and other fields. For example, in the field of nonlinear optics, nanosecond lasers can achieve high-intensity laser pulse output. Since the damage threshold of the material is proportional to the laser pulse width, short-pulse lasers are required. In the field of laser ranging, short pulses reduce measurement errors, resulting in higher measurement accuracy. In the field of laser processing, nanosecond lasers have higher power, and longer pulse widths can achieve full dissolution of the processed materials, resulting in higher processing efficiency.

[0003] Commonly used nanosecond Q-switched lasers are generally single continuous pulse lasers, and the output pulse lasers are certain. For example, the use of acousto-optic Q-switching technology can generally obtain hundreds of nanosecond laser pulse outputs, and the use of electro-optic Q-switching technology can generally obtain tens of nanosecond laser pulse outputs. In actual production and life, for different target material application scenarios, a single continuous pulse laser is difficult to meet the actual production and life needs, and composite nanosecond pulse outputs with different pulse widths are urgently needed to cope with different target material application scenarios. Summary of the invention

[0004] The invention provides a composite pulse laser device, which is used to solve the defect of single output pulse width of nanosecond Q-switched laser in the prior art, and realizes the output of laser pulses with different pulse widths.

[0005] The invention provides a composite pulse laser device, comprising an output mirror, a polarizing plate, a laser gain module, a first reflecting mirror, a first Q switch, a second reflecting mirror, a second Q switch and a controller, wherein the output mirror is used for outputting a laser beam; the polarizing plate is used for transmitting a first-direction polarized laser and reflecting a second-direction polarized laser; the laser gain module is located between the output mirror and the polarizing plate and is used for radiating laser; the first reflecting mirror and the first Q switch are located at a first-direction input side of the polarizing plate, the first reflecting mirror, the first Q switch, the polarizing plate and the output mirror are sequentially arranged at intervals to form a first pulse laser resonant arm cavity; the second reflecting mirror and the second Q switch are located at a second-direction input side of the polarizing plate, the second reflecting mirror, the second Q switch, the polarizing plate and the output mirror are sequentially arranged at intervals to form a second pulse laser resonant arm cavity; the controller controls the first Q switch and the second Q switch respectively to adjust the laser pulse timing intervals in the first pulse laser resonant arm cavity and the second pulse laser resonant arm cavity.

[0006] According to a composite pulse laser device provided by the present invention, the first Q switch is an electro-optical Q switch to generate a laser pulse of tens of nanoseconds in the first pulse laser resonant arm cavity; the second Q switch is an acousto-optic Q switch to generate a laser pulse of hundreds of nanoseconds in the second pulse laser resonant arm cavity.

[0007] According to a composite pulse laser device provided by the present invention, the first Q switch adopts a de-voltage Q-switching method, and the electro-optical crystal in the first Q switch includes a high-voltage state and a low-voltage state. In the high-voltage state, the polarization direction of the laser beam passing through the electro-optical crystal is rotated 90°, and the laser beam is blocked in the first pulse laser resonant arm cavity; in the low-voltage state, the polarization direction of the laser beam passing through the electro-optical crystal remains unchanged, and the laser beam forms an effective laser oscillation in the first pulse laser resonant arm cavity.

[0008] According to a composite pulse laser device provided by the present invention, the first Q switch adopts a boost-type Q-switching method, a 1 / 4λ wave plate is arranged between the first Q switch and the polarizer, and the electro-optical crystal in the first Q switch includes a high-pressure state and a low-pressure state. In the low-pressure state, the polarization direction of the laser light beam passing through the electro-optical crystal remains unchanged, and the polarization direction is rotated 90° after passing through the 1 / 4λ wave plate, and the laser light beam is blocked in the first pulse laser resonant arm cavity; in the high-pressure state, the polarization direction of the laser light beam passing through the electro-optical crystal is rotated 90°, and the polarization direction is further rotated 90° after passing through the 1 / 4λ wave plate, and the laser light beam forms an effective laser oscillation in the first pulse laser resonant arm cavity.

[0009] According to a composite pulse laser device provided by the present invention, the first-direction polarized laser is horizontally polarized light, the second-direction polarized laser is vertically polarized light, and the polarizer forms an angle of 45° with the horizontal direction.

[0010] The first reflecting mirror, the first Q switch, the polarizing plate, the laser gain module and the output mirror are sequentially arranged at intervals in the horizontal direction so that the polarizing plate transmits the horizontal linear polarized light.

[0011] The second reflector and the second Q switch generate the vertical linear polarized light, which is reflected by the polarizer and enters the laser gain module.

[0012] According to a composite pulse laser device provided by the present invention, a half-wave plate is arranged between the laser gain module and the polarizer, and the half-wave plate is used to change the energy distribution ratio of the first-direction polarized laser and the second-direction polarized laser to adjust the intensity of the two pulse lasers.

[0013] According to a composite pulse laser device provided by the present invention, the laser gain module includes a laser gain medium and a pump source, and the pump light emitted by the pump source is injected into the laser gain medium to generate laser in the laser gain medium.

[0014] According to a composite pulse laser device provided by the present invention, the laser gain medium of the laser gain module includes an isotropic crystal and / or an anisotropic crystal, the isotropic crystal is used to form a single-wavelength laser output of the first-direction polarized laser and the second-direction polarized laser, and the anisotropic crystal is used to form a different-wavelength laser output of the first-direction polarized laser and the second-direction polarized laser.

[0015] According to a composite pulse laser device provided by the present invention, the pumping mode of the pump source adopts side pumping or end pumping.

[0016] According to a composite pulse laser device provided by the present invention, the polarizer is a thin-film polarizer or a polarization beam splitter prism.

[0017] The composite pulse laser device provided by the present invention forms a first pulse laser resonant arm cavity through a first reflector, a first Q switch, a polarizer and an output mirror, forms a second pulse laser resonant arm cavity through a second reflector, a second Q switch, a polarizer and an output mirror, transmits a first-direction polarized laser through the polarizer, and reflects a second-direction polarized laser through the polarizer, and can output pulse lasers of tens of nanoseconds and hundreds of nanoseconds from a laser gain module and an output mirror, and controls the output of the pulse lasers of the first pulse laser resonant arm cavity and the second pulse laser resonant arm cavity through a controller to realize flexible and adjustable pulse intervals. The composite pulse laser device of the present invention has a compact structure and flexible design, can simultaneously realize pulse laser outputs of tens of nanoseconds and hundreds of nanoseconds under the control of the same electrical signal, and has strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 This is one of the structural schematic diagrams of the composite pulse laser device provided by the present invention.

[0020] Figure 2 This is the second structural schematic diagram of the composite pulse laser device provided by the present invention.

[0021] Figure 3It is a schematic diagram of the composite pulse outputted by the first embodiment of the present invention.

[0022] Figure 4 It is a schematic diagram of the composite pulse outputted by the second embodiment of the present invention.

[0023] Figure 5 It is a schematic diagram of the composite pulse outputted by the third embodiment of the present invention.

[0024] Figure numerals: 1, output mirror; 2, polarizer; 3, laser gain module; 4, first reflector; 5, first Q switch; 6, second reflector; 7, second Q switch; 8, controller; 9, 1 / 4λ wave plate; 10, half-wave plate. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limitations on the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0027] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral 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. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0028] In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "above" or "below" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0029] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0030] Combine the following Figures 1 to 5 The specific structure and working process of the composite pulse laser device of the present invention are described.

[0031] One embodiment of the present invention provides a composite pulse laser device, see Figure 1 As shown, it includes an output mirror 1, a polarizer 2, a laser gain module 3, a first reflector 4, a first Q switch 5, a second reflector 6, a second Q switch 7 and a controller 8, wherein the output mirror 1 is used to output a laser beam; the polarizer 2 is used to transmit a first-direction polarized laser and reflect a second-direction polarized laser; the laser gain module 3 is located between the output mirror 1 and the polarizer 2 and is used to radiate laser; the first reflector 4 and the first Q switch 5 are located on the first-direction input side of the polarizer 2, and the first reflector 4, the first Q switch 5, the polarizer 2 and the output mirror 1 are arranged in sequence to form a first pulse laser resonant arm cavity; the second reflector 6 and the second Q switch 7 are located on the second-direction input side of the polarizer 2, and the second reflector 6, the second Q switch 7, the polarizer 2 and the output mirror 1 are arranged in sequence to form a second pulse laser resonant arm cavity; the controller 8 is respectively connected to and controls the first Q switch 5 and the second Q switch 7 to adjust the laser pulse timing interval in the first pulse laser resonant arm cavity and the second pulse laser resonant arm cavity.

[0032] It can be understood that the composite pulse laser device of this embodiment forms a first pulse laser resonant arm cavity through the first reflector 4, the first Q switch 5, the polarizer 2 and the output mirror 1, and forms a second pulse laser resonant arm cavity through the second reflector 6, the second Q switch 7, the polarizer 2 and the output mirror 1. The polarizer 2 transmits the polarized laser in the first direction and reflects the polarized laser in the second direction. The laser gain module 3 and the output mirror 1 can output pulse lasers of tens of nanoseconds and hundreds of nanoseconds. The controller 8 controls the output of the pulse lasers of the first pulse laser resonant arm cavity and the second pulse laser resonant arm cavity to achieve flexible and adjustable pulse interval. The device has a compact structure and flexible design. It can simultaneously achieve pulse laser outputs of tens of nanoseconds and hundreds of nanoseconds under the control of the same electrical signal, and has strong practicality.

[0033] In some embodiments of the composite pulse laser device of the present invention, the first Q switch 5 is an electro-optical Q switch to generate a laser pulse of tens of nanoseconds in the first pulse laser resonant arm cavity; the second Q switch 7 is an acousto-optic Q switch to generate a laser pulse of hundreds of nanoseconds in the second pulse laser resonant arm cavity.

[0034] It is understandable that the electro-optical Q switch utilizes the electro-optic effect (i.e., the phenomenon that the refractive index of certain crystals changes under the action of an external electric field). When no voltage is applied to the electro-optical crystal, the crystal has a high loss to the laser beam passing through it, preventing the laser from oscillating. When an appropriate voltage is applied, the refractive index of the crystal changes, allowing the beam to pass through. At this time, the loss in the laser cavity suddenly decreases, and the energy stored in the laser medium is rapidly released to form a laser pulse with a high peak power. The first Q switch 5 uses an electro-optical Q switch, which can generate a laser pulse of ten nanoseconds in the first pulse laser resonant arm cavity.

[0035] The acousto-optic Q switch works based on the acousto-optic effect, that is, when ultrasound passes through a specific crystal (such as quartz), a periodic change in the refractive index is formed in the crystal, which is equivalent to a dynamic diffraction grating. When there is no ultrasound, the laser beam cannot pass through the crystal effectively because the loss is high at this time. Once the ultrasound is activated, the dynamic grating formed will allow the laser beam of a specific wavelength to pass through, while reducing the loss in the laser cavity, thereby triggering strong laser oscillations. The second Q switch 7 uses an acousto-optic Q switch, which can generate laser pulses of hundreds of nanoseconds in the second pulse laser resonant arm cavity.

[0036] Specifically, in some specific examples of the composite pulse laser device of the present invention, the first Q switch 5 adopts a de-voltage Q-switching method, and the electro-optical crystal in the first Q switch 5 includes a high-voltage state and a low-voltage state. In the high-voltage state, the polarization direction of the laser light beam passing through the electro-optical crystal is rotated 90°, and the laser light beam is blocked in the first pulse laser resonant arm cavity; in the low-voltage state, the polarization direction of the laser light beam passing through the electro-optical crystal remains unchanged, and the laser light beam forms an effective laser oscillation in the first pulse laser resonant arm cavity.

[0037] It is understandable that the first Q switch 5 (electro-optical Q switch) can generate high-energy, short-pulse-width laser pulses by using a depressurized Q-switching method. In the initial state, the electro-optical Q switch (EOQ) is in a high-voltage state. At this time, the refractive index of the electro-optical crystal changes under the action of an external electric field, causing the polarization direction of the laser beam passing through the electro-optical crystal to rotate by 90°. This rotation of the polarization direction prevents the laser beam from passing through the polarizer 2 or other polarization selection elements in the first pulse laser resonant arm cavity, so the laser beam is blocked in the first pulse laser resonant arm cavity and cannot form effective laser oscillation. In the high-voltage state, the energy of the laser gain medium in the laser gain module 3 continues to accumulate, but due to the rotation of the polarization direction, the laser beam cannot pass through the first pulse laser resonant arm cavity, and the energy is mainly stored in the laser medium. When it is necessary to generate a laser pulse, the controller 8 quickly reduces the voltage of the electro-optical Q switch to a low voltage state. At this time, the refractive index of the electro-optical crystal returns to its initial state and no longer causes the rotation of the polarization direction. The polarization direction of the laser beam remains unchanged and can smoothly pass through the polarizer 2 or other polarization selection elements in the first pulse laser resonant arm cavity, thereby forming an effective laser oscillation in the first pulse laser resonant arm cavity. As the laser oscillation is established, the energy stored in the laser gain medium of the laser gain module 3 is rapidly released to form a high-energy, short pulse width laser pulse, which is output through the output mirror 1.

[0038] In some other specific examples of the composite pulse laser device of the present invention, the first Q switch 5 adopts a boost-type Q-switching method, a 1 / 4λ wave plate 9 is arranged between the first Q switch 5 and the polarizer 2, and the electro-optical crystal in the first Q switch 5 includes a high-pressure state and a low-pressure state. In the low-pressure state, the polarization direction of the laser light beam passing through the electro-optical crystal remains unchanged, and the polarization direction is rotated 90° after passing through the 1 / 4λ wave plate 9, and the laser light beam is blocked in the first pulse laser resonant arm cavity; in the high-pressure state, the polarization direction of the laser light beam passing through the electro-optical crystal is rotated 90°, and the polarization direction is rotated again 90° after passing through the 1 / 4λ wave plate 9, and the laser light beam forms an effective laser oscillation in the first pulse laser resonant arm cavity.

[0039] It can be understood that the first Q switch 5 adopts a boost-type Q-switching method, and realizes precise control of the laser pulse by inserting a 1 / 4λ wave plate 9 in the first pulse laser resonant arm cavity. In the initial state, the electro-optical Q switch (EOQ) is in a low-voltage state. At this time, the refractive index of the electro-optical crystal is not affected by the external electric field, and the polarization direction of the laser beam remains unchanged when passing through the electro-optical crystal. The 1 / 4λ wave plate 9 inserted in the first pulse laser resonant arm cavity will rotate the polarization direction of the passing laser beam by 90°. Specifically, the linear polarized light becomes circularly polarized light after passing through the 1 / 4λ wave plate 9, and then returns to the 1 / 4λ wave plate 9 after passing through the electro-optical crystal, and becomes linearly polarized light again, but the polarization direction is rotated by 90°. In the low-voltage state, the polarization direction of the laser beam remains unchanged when passing through the electro-optical crystal, but the polarization direction rotates by 90° after passing through the 1 / 4λ wave plate 9. This makes it impossible for the laser beam to pass through the polarizer 2 or other polarization selection elements in the first pulse laser resonant arm cavity, so the laser beam is blocked in the first pulse laser resonant arm cavity and cannot form effective laser oscillation. Therefore, the energy of the laser gain medium in the laser gain module 3 continues to accumulate, but due to the rotation of the polarization direction, the first pulse laser resonant arm cavity cannot generate laser light. At this time, the energy is mainly stored in the laser gain medium. When it is necessary to generate a laser pulse, the controller 8 quickly raises the voltage of the electro-optical Q switch to a high voltage state. At this time, the refractive index of the electro-optical crystal changes under the action of the external electric field, causing the polarization direction of the laser beam passing through the electro-optical crystal to no longer rotate. As a result, the polarization direction of the laser beam remains unchanged and can smoothly pass through the polarizer 2 or other polarization selection elements in the first pulse laser resonant arm cavity, thereby forming effective laser oscillation in the first pulse laser resonant arm cavity. As the laser oscillation is established, the energy stored in the laser gain medium is rapidly released to form a high-energy, short-pulse-width laser pulse, which is output through the output mirror 1.

[0040] In some embodiments of the composite pulse laser device of the present invention, the first reflector 4 and the first Q switch 5 are located in the first pulse laser resonant arm cavity, the second reflector 6 and the second Q switch are located in the second pulse laser resonant arm cavity, the first pulse laser resonant arm cavity generates a first direction polarized laser, the second pulse laser resonant arm cavity generates a second direction polarized laser, the first direction polarized laser is horizontally polarized light, the second direction polarized laser is vertically polarized light, the polarizer 2 is at an angle of 45° with the horizontal direction, the polarizer 2 transmits horizontally polarized light and reflects vertically polarized light, whereby after the gain medium 3 is excited by the pump light, laser outputs of tens of nanoseconds and hundreds of nanoseconds can be generated respectively.

[0041] Further, in some embodiments, a half-wave plate 10 is arranged between the laser gain module 3 and the polarizer 2, and the half-wave plate 10 is used to change the energy distribution ratio of the first direction polarized laser and the second direction polarized laser to adjust the intensity of the two pulsed lasers. It can be understood that the combination of the half-wave plate 10 and the polarizer 2 can simultaneously achieve adjustable intensity of the two pulsed lasers, wherein the half-wave plate 10 can rotate the polarization direction of the light, and the polarizer 2 can select the polarization direction of the transmission, and the combination of the half-wave plate 10 and the polarizer 2 can achieve continuous adjustment of the light energy.

[0042] In some embodiments of the composite pulse laser device of the present invention, the laser gain module 3 includes a laser gain medium and a pump source, the pump mode of the pump source can be side pumping or end pumping, the pump light emitted by the pump source is injected into the laser gain medium, and laser light is generated in the laser gain medium. The laser gain medium of the laser gain module 3 includes an isotropic crystal and / or an anisotropic crystal, the isotropic crystal is used to form a single wavelength laser output of a first direction polarized laser and a second direction polarized laser, and the anisotropic crystal is used to form a different wavelength laser output of a first direction polarized laser and a second direction polarized laser. Specifically, after passing through the polarizer 2, a first-direction polarized laser and a second-direction polarized laser output are formed. When the laser gain module 3 adopts an isotropic crystal, the isotropic crystal will not preferentially select a specific polarization direction after being excited by laser pumping or other forms of light, forming a single-wavelength laser output; when the laser gain module 3 adopts an anisotropic crystal, after being excited by laser pumping or other forms of light, the anisotropic crystal has an asymmetric structure inside the anisotropic crystal, resulting in differences in its optical properties in different directions, forming laser outputs with different wavelengths and different polarization states.

[0043] It is understandable that the laser gain module 3 can achieve laser output with different polarization directions and wavelengths by selecting appropriate laser gain media and pumping modes. Isotropic crystals are suitable for laser output with a single wavelength, and common isotropic crystals include Nd:YAG (neodymium-doped yttrium aluminum garnet) and Nd:glass (neodymium-doped glass); while anisotropic crystals are suitable for laser output with different wavelengths, and common anisotropic crystals include Nd:YVO4 (neodymium-doped yttrium vanadate) and Ti:Sapphire (titanium sapphire). The choice of pumping mode (side pumping or end pumping) depends on the specific application needs and performance requirements of the laser. The pumping light enters from the side of the laser gain medium and is usually pumped by LD bars and bulbs. It is commonly used in isotropic crystal laser gain media and is suitable for high-power lasers. It can provide uniform pumping distribution; the pumping light enters from one end of the laser gain medium and is usually pumped by a single fiber coupling method to pump crystal rods or chips. It is commonly used in isotropic crystal laser gain media and is suitable for miniaturized and high-efficiency lasers. It can achieve higher pumping efficiency and better beam quality.

[0044] In some embodiments of the composite pulse laser device of the present invention, the polarizer 2 may be a thin film polarizer or a polarization beam splitter prism. The polarizer 2 plays a key role in polarization control in the composite pulse laser device, and a thin film polarizer or a polarization beam splitter prism may be selected according to specific requirements. These two polarizers each have advantages and disadvantages and are suitable for different application scenarios.

[0045] Among them, thin-film polarizers are usually composed of multiple layers of transparent materials (such as plastic or glass) with different refractive indices, and the surface is coated with one or more layers of thin films, which have the characteristics of selective transmission or reflection of light in a specific polarization direction. When linearly polarized light is incident on a thin-film polarizer, light in a specific polarization direction (polarized laser in the first direction) will be transmitted, while polarized light in the vertical direction (polarized laser in the second direction) will be reflected. In this way, the thin-film polarizer can selectively transmit light in the desired polarization direction, thereby achieving polarization control. Thin-film polarizers are relatively low in cost, easy to integrate into laser systems, and can be designed to have a wide operating wavelength range.

[0046] Polarization beam splitter (PBS) is usually made of two right-angle prisms glued together with a layer of polarization beam splitter film in between. The polarization beam splitter film has the characteristics of selective transmission or reflection of light in a specific polarization direction. When linear polarized light is incident on the polarization beam splitter, light in a specific polarization direction (polarized laser in the first direction) will be transmitted, while polarized light in the vertical direction (polarized laser in the second direction) will be reflected. In this way, the polarization beam splitter can selectively transmit light in the desired polarization direction, thereby achieving polarization control. The polarization beam splitter is not very sensitive to changes in the incident angle and is suitable for a larger range of angle changes. It has high transmittance and reflectivity, is suitable for high-power laser applications, and can achieve a high extinction ratio, that is, the contrast between transmitted light and reflected light.

[0047] The composite pulse laser device of the present invention is further described below in conjunction with specific embodiments.

[0048] Embodiment 1: Figure 1 An embodiment structure of the composite pulse laser device of the present invention is shown, which is a pulse laser device combining electro-optical de-stressing Q switching and acousto-optic Q switching, including an output mirror 1, a polarizer 2, a laser gain module 3, a first reflector 4, a first Q switch 5, a second reflector 6, a second Q switch 7, a controller 8, a half-wave plate 10 and a water cooling device (not marked in the figure).

[0049] The first reflector 4, the first Q switch 5, the polarizer 2 and the output mirror 1 form the first pulse laser resonant arm cavity, and the second reflector 6, the second Q switch 7, the polarizer 2 and the output mirror 1 form the second pulse laser resonant arm cavity, wherein the polarizer 2 is used to transmit the polarized laser in the first direction and reflect the polarized laser in the second direction, the polarized laser in the first direction is horizontally polarized light, and the polarized laser in the second direction is vertically polarized light. The laser gain module 3 is placed in the resonant cavity to generate oscillating laser; the half-wave plate 10 is combined with the polarizer 2 to adjust the intensity of the output laser pulse; the first Q switch 5 (electro-optical Q switch) is placed in the first pulse laser resonant arm cavity to generate laser pulses of tens of nanoseconds, and the second Q switch 7 (acousto-optical Q switch) is placed in the second pulse laser resonant arm cavity to generate laser pulses of hundreds of nanoseconds. The controller 8 outputs an electrical signal to control the first Q switch 5 and the second Q switch 7. The first Q switch 5 is a depressurized electro-optical Q switch. When the voltage is high, the polarization direction of the laser traveling back and forth between the electro-optical Q switch is rotated by 90°. When the voltage is low, the polarization direction remains unchanged, that is, the laser pulse is output. The output laser is a 1064 nm tens of nanosecond pulse laser. The second Q switch 7 is an acousto-optic Q switch, and the output laser is a 1064 nm hundreds of nanosecond pulse laser. The half-wave plate 10 is placed between the laser gain module 3 and the polarizer 2, and is combined with the polarizer 2. By rotating the half-wave plate 10, the energy distribution ratio of the first-direction polarized laser and the second-direction polarized laser is changed to adjust the intensity of the two-way laser pulse. The water cooling device acts on the laser gain medium of the laser gain module 3, and is mainly water-cooled by cooling water to avoid excessive temperature in the laser gain medium, which causes a decrease in the power and beam quality of the laser output.

[0050] The laser gain module 3 includes a quasi-continuously operated semiconductor 808 nm laser pump source, the laser gain medium is a Nd:YAG crystal, and a quasi-continuous 1064 nm laser is output by side pumping; the laser gain medium is a Nd:YAG crystal rod, the doping concentration is 1%, the size is D3 mm × 80 mm, and the crystal surface is coated with 808 nm and 1064 nm high-transmittance films (transmittance greater than 99%); the output mirror 1 is coated with a 1064 nm high-reflection film (reflectivity greater than 90%); the first reflector 4 and the second reflector 6 are coated with a 1064 nm high-reflection film (reflectivity greater than 99%).

[0051] Specifically, the laser gain module 3 radiates 1064 nm laser by side pumping, oscillates in the resonant cavity to form laser, the polarizer 2 transmits horizontal linear polarized light, reflects vertical linear polarized light, and forms a first pulse laser resonant arm cavity and a second pulse laser resonant arm cavity with the first reflector 4 and the second reflector 6, so as to realize the operation of two 1064 nm fundamental frequency light of horizontal linear polarized light and vertical linear polarized light; the first Q switch 5 and the second Q switch 7 are respectively placed in the first pulse laser resonant arm cavity and the second pulse laser resonant arm cavity, and are controlled by the controller 8 outputting an electrical signal; the first Q switch 5 (electro-optical Q switch) outputs a 1064 nm laser with a pulse width of 10 ns and a frequency of 500 Hz, and the second Q switch 7 (acousto-optical Q switch) outputs a 1064 nm laser with a pulse width of 100 ns and a frequency of 500 Hz. The controller 8 adjusts the relative delay between the first Q switch 5 and the second Q switch 7 to 1 ms, and outputs a composite pulse with a frequency of 500 Hz asymmetric pulse, wherein the frequency between pulses with different pulse widths is 1 kHz, and rotate the half-wave plate to change the angle at the same time to control the intensities of the two polarized lasers to be equal; finally, nanosecond pulse lasers with different pulse widths, the same intensity and the same pulse interval are output through the output mirror 1, such as Figure 3 shown.

[0052] In this embodiment, the resonant cavity is composed of an input mirror 1, a polarizer 2, a first reflector 4 and a second reflector 6; nanosecond pulse outputs of two pulse widths are realized by electro-optical Q switching and acousto-optic Q switching; the delay time of the controller 8 outputting the electrical signal is adjusted to achieve adjustable intervals of nanosecond pulses of the same pulse width; combined with the half-wave plate 10 and the polarizer 2, the pulse intensity of the two pulse widths can be adjusted. Therefore, the composite pulse laser device of this embodiment has the advantages of compact structure and high Q-switched laser conversion efficiency.

[0053] Embodiment 2: Figure 2 Another embodiment structure of the composite pulse laser device of the present invention is shown, which is a pulse laser device combining boost Q switching and acousto-optic Q switching, including an output mirror 1, a polarizer 2, a laser gain module 3, a first reflector 4, a first Q switch 5, a second reflector 6, a second Q switch 7, a controller 8, a half-wave plate 10 and a water cooling device (not marked in the figure).

[0054] The structure of the composite pulse laser device in this embodiment is mostly the same as that of the first embodiment. The difference is that in this embodiment, the first Q switch 5 is a boosted electro-optical Q-switching method. At this time, a 1 / 4λ wave plate 9 is also inserted into the first pulse laser resonant arm cavity. When the pressure is low, the polarization direction of the laser traveling back and forth between the first Q switch 5 and the 1 / 4λ wave plate 9 is rotated by 90°. When the pressure is high, the polarization direction remains unchanged, that is, the laser pulse is output, and the output laser is a 1064 nm tens of nanosecond laser.

[0055] Specifically, the laser gain device 3 radiates 1064 nm laser by side pumping, oscillates in the resonant cavity to form laser, the polarizer 2 transmits horizontal linear polarized light and reflects vertical linear polarized light, and together with the first reflector 4 and the second reflector 6, forms the first pulse laser resonant arm cavity and the second pulse laser resonant arm cavity, realizing the operation of two 1064 nm fundamental frequency light of horizontal linear polarized light and vertical linear polarized light; the first Q switch 5 and the second Q switch 7 are respectively placed in the first pulse laser resonant arm cavity and the second pulse laser resonant arm cavity, and are controlled by the controller 8 outputting electrical signals; the first Q switch 5 (electro-optical Q switch) outputs a 1064 nm laser with a pulse width of 10 ns and a frequency of 500 Hz, and the second Q switch 7 (acousto-optical Q switch) outputs a 1064 nm laser with a pulse width of 100 ns and a frequency of 500 Hz. The controller 8 adjusts the relative delay to 0.5 ms, outputs a composite pulse frequency of 500 Hz asymmetric pulses, where the frequency between pulses with different pulse widths is 2 kHz, and changes the angle of the half-wave plate 10 at the same time to control the intensities of the two polarized lasers to be equal; finally, nanosecond pulse lasers with different pulse widths, the same intensity and different pulse intervals are output through the output mirror 1, as shown in FIG. Figure 4 shown.

[0056] Embodiment 3: This embodiment adopts the same structure as Embodiment 2, except that, in this embodiment, the laser gain module 3 includes a quasi-continuously operated semiconductor 980nm laser pump source, the laser gain medium is a Yb:KGW crystal, and a quasi-continuous 1028nm laser and a 1037nm laser are output by side pumping; the laser gain medium is a Yb:KGW crystal rod, the size is D3 mm × 10mm, the doping concentration is 3%, and the crystal surface is coated with 980 nm, 1028 nm and 1037 nm high-transmittance films (transmittance greater than 99%); the output mirror 1 is coated with 1028 nm and 1037 nm high-reflection films (reflectivity greater than 90%); the first reflector 4 and the second reflector 6 are coated with 1028 nm and 1037 nm high-reflection films (reflectivity greater than 99%).

[0057] The first Q switch 5 adopts a boosted electro-optical Q-switching method. At this time, a 1 / 4λ wave plate 9 is also inserted into the first pulse laser resonant arm cavity. When the voltage is low, the polarization direction of the laser traveling back and forth between the first Q switch 5 and the 1 / 4λ wave plate 9 is rotated by 90°. When the voltage is high, the polarization direction remains unchanged, that is, the laser pulse is output. The output laser is a 1028 nm tens of nanosecond pulse laser.

[0058] Specifically, the laser gain device 3 radiates 1064 nm laser by side pumping, oscillates in the resonant cavity to form laser, the polarizer 2 transmits horizontal linear polarized light and reflects vertical linear polarized light, and together with the first reflector 4 and the second reflector 6, forms the first pulse laser resonant arm cavity and the second pulse laser resonant arm cavity, realizing the operation of two 1064 nm fundamental frequency light of horizontal linear polarized light and vertical linear polarized light; the first Q switch 5 and the second Q switch 7 are respectively placed in the first pulse laser resonant arm cavity and the second pulse laser resonant arm cavity, and are controlled by the controller 8 outputting electrical signals; the first Q switch 5 (electro-optical Q switch) outputs a 1028 nm laser with a pulse width of 10 ns and a frequency of 500 Hz, and the second Q switch 7 (acousto-optical Q switch) outputs a 1037 nm laser with an output pulse width of 100 ns and a frequency of 500 Hz, the controller 8 adjusts the relative delay to 0.5 ms, and outputs a composite pulse with a frequency of 500 Hz asymmetric pulses, wherein the frequency between pulses with different pulse widths is 2 kHz, and at the same time change the angle of the half-wave plate 10 to control the intensities of the two polarized lasers to be unequal; finally, nanosecond pulse lasers with different pulse widths, intensities and pulse intervals are output through the output mirror 1, such as Figure 5 shown.

[0059] Through the specific description of the above embodiments 1 to 3, and in combination with Figure 3 , Figure 4 and Figure 5 It can be seen that the composite pulse laser device provided by the present invention is a composite pulse laser device that can output different pulse widths and has adjustable pulse interval and intensity. The laser gain module 3, the Q switch (the first Q switch 5 and the second Q switch 7), the half-wave plate 10 and the polarizer 2 form two pulse laser resonant arm cavities in the same resonant cavity, and the structure is compact; the polarizer 2 transmits horizontal polarized light and reflects vertical polarized light, and together with the cavity mirrors (the output mirror 1, the first reflector 4, and the second reflector 6) form cavity arms respectively; the Q switch is an electro-optical Q switch and an acousto-optic Q switch controlled by the same controller 8, the electro-optical Q switch is placed in the first pulse laser resonant arm cavity, and the acousto-optic Q switch is placed in the second pulse laser resonant arm cavity, which can respectively realize pulse laser output of tens of nanoseconds and hundreds of nanoseconds; the output of the pulse laser is controlled by an electrical signal of the controller 8 to realize flexible and adjustable pulse interval; the half-wave plate 10 and the polarizer 2 are combined to simultaneously realize adjustable intensity of the two pulse lasers. The structure is compact and flexible in design. Under the control of the same electrical signal, it can simultaneously achieve pulse laser output of tens of nanoseconds and hundreds of nanoseconds. The pulse interval and intensity of different pulse widths can be flexibly adjusted, which makes it very practical.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite pulse laser device, characterized in that: include: An output mirror (1), used for outputting a laser beam; A polarizing plate (2) for transmitting laser light polarized in a first direction and reflecting laser light polarized in a second direction; A laser gain module (3), located between the output mirror (1) and the polarizer (2), and used for radiating laser light; A first reflecting mirror (4) and a first Q switch (5) are located on the first direction input side of the polarizer (2), and the first reflecting mirror (4), the first Q switch (5), the polarizer (2) and the output mirror (1) are arranged in sequence and spaced apart to form a first pulse laser resonant arm cavity; A second reflecting mirror (6) and a second Q switch (7) are located on the second direction input side of the polarizer (2), and the second reflecting mirror (6), the second Q switch (7), the polarizer (2) and the output mirror (1) are arranged in sequence and spaced apart to form a second pulse laser resonant arm cavity; A controller (8) controls the first Q switch (5) and the second Q switch (7) respectively to adjust the laser pulse timing intervals in the first pulse laser resonant arm cavity and the second pulse laser resonant arm cavity.

2. The composite pulse laser device according to claim 1, characterized in that: The first Q switch (5) is an electro-optical Q switch, which generates a laser pulse of ten nanoseconds in the first pulse laser resonant arm cavity; and the second Q switch (7) is an acousto-optical Q switch, which generates a laser pulse of one hundred nanoseconds in the second pulse laser resonant arm cavity.

3. The composite pulse laser device according to claim 2, characterized in that: The first Q switch (5) adopts a de-stressed Q-switching method. The electro-optical crystal in the first Q switch (5) includes a high-pressure state and a low-pressure state. In the high-pressure state, the polarization direction of the laser beam passing through the electro-optical crystal is rotated by 90 degrees, and the laser beam is blocked in the first pulse laser resonant arm cavity; in the low-pressure state, the polarization direction of the laser beam passing through the electro-optical crystal remains unchanged, and the laser beam forms an effective laser oscillation in the first pulse laser resonant arm cavity.

4. The composite pulse laser device according to claim 2, characterized in that: The first Q switch (5) adopts a boost-type Q-switching method. A 1 / 4λ wave plate (9) is arranged between the first Q switch (5) and the polarizing plate (2). The electro-optical crystal in the first Q switch (5) includes a high-pressure state and a low-pressure state. In the low-pressure state, the polarization direction of the laser light beam passing through the electro-optical crystal remains unchanged. After passing through the 1 / 4λ wave plate (9), the polarization direction rotates 90°, and the laser light beam is blocked in the first pulse laser resonant arm cavity. In the high-pressure state, the polarization direction of the laser light beam passing through the electro-optical crystal rotates 90°. After passing through the 1 / 4λ wave plate (9), the polarization direction rotates another 90°, and the laser light beam forms an effective laser oscillation in the first pulse laser resonant arm cavity.

5. The composite pulse laser device according to claim 2, characterized in that: The first-direction polarized laser light is horizontally polarized light, the second-direction polarized laser light is vertically polarized light, and the polarizer (2) forms an angle of 45° with the horizontal direction; The first reflector (4), the first Q switch (5), the polarizer (2), the laser gain module (3) and the output mirror (1) are arranged in sequence and spaced apart in a horizontal direction, so that the polarizer (2) transmits the horizontal linear polarized light; The second reflector (6) and the second Q switch (7) generate the vertical linear polarized light, which is reflected by the polarizer (2) and enters the laser gain module (3).

6. The composite pulse laser device according to claim 5, characterized in that: A half-wave plate (10) is arranged between the laser gain module (3) and the polarizing plate (2), and the half-wave plate (10) is used to change the energy distribution ratio of the laser light polarized in the first direction and the laser light polarized in the second direction, so as to adjust the intensity of the two pulsed laser lights.

7. The composite pulse laser device according to any one of claims 1 to 6, characterized in that: The laser gain module (3) comprises a laser gain medium and a pump source, and pump light emitted by the pump source is injected into the laser gain medium to generate laser light in the laser gain medium.

8. The composite pulse laser device according to claim 7, characterized in that: The laser gain medium of the laser gain module (3) comprises an isotropic crystal and / or an anisotropic crystal, wherein the isotropic crystal is used to form a single-wavelength laser output of the first-direction polarized laser and the second-direction polarized laser, and the anisotropic crystal is used to form a different-wavelength laser output of the first-direction polarized laser and the second-direction polarized laser.

9. The composite pulse laser device according to claim 7, characterized in that: The pumping mode of the pump source adopts side pumping or end pumping.

10. The composite pulse laser device according to any one of claims 1 to 6, characterized in that: The polarizer (2) is a thin-film polarizer or a polarization splitter prism.

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